Mobile Application Development Chapter 5: Working with Android Media Player

MOBILE APPLICATION

DEVELOPMENT

Chapter 5

Android Media Player

•

We can play and control the audio files in

android by the help of 

MediaPlayer class

.

•

Here, we are going to see a simple example to

play the audio file. In the next page, we will

see the example to control the audio playback

like start, stop, pause etc.

•

MediaPlayer class

–

The 

android.media.MediaPlayer

 class is used to

control the audio or video files.

•

Methods of MediaPlayer class

–

There are many methods of MediaPlayer class.

Some of them are as follows:

Activity class

•

Let's write the code of to play the audio file.

Here, we are going to play maine.mp3 file located

inside the sdcard/Music directory.

•

File: MainActivity.java

package

 com.example.audiomediaplayer1;

import

 android.media.MediaPlayer;

import

 android.net.Uri;

import

 android.os.Bundle;

import

 android.app.Activity;

import

 android.view.Menu;

import

 android.widget.MediaController;

import

 android.widget.VideoView;

public

class

 MainActivity 

extends

 Activity {

    @Override

protected

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        MediaPlayer mp=

new

 MediaPlayer();

try

{

            mp.setDataSource("/sdcard/Music/maine.mp3");//Write your location here

            mp.prepare();

            mp.start();

        }

catch

(Exception e){e.printStackTrace();}

    }

    @Override

public

boolean

 onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.activity_main, menu);

return

true

;

    }

}

Android MediaPlayer Example of

controlling the audio

•

activity_main.xml

–

Drag three buttons from palette to start, stop and

pause the audio play. Now the xml file will look

like this:

MainActivity.java

package

 com.example.audioplay;

import

 android.media.MediaPlayer;

import

 android.os.Bundle;

import

 android.os.Environment;

import

 android.app.Activity;

import

 android.view.Menu;

import

 android.view.View;

import

 android.view.View.OnClickListener;

import

 android.widget.Button;

public

class

 MainActivity 

extends

 Activity {

    Button start,pause,stop;

    @Override

protected

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

 start=(Button)findViewById(R.id.button1);

        pause=(Button)findViewById(R.id.button2);

        stop=(Button)findViewById(R.id.button3);

        //creating media player

final

 MediaPlayer mp=

new

 MediaPlayer();

try

{

                //you can change the path, here path is external directory(e

.g. sdcard) /Music/maine.mp3

        mp.setDataSource(Environment.getExternalStorageDirectory().g

etPath()+"/Music/maine.mp3");

        mp.prepare();

        }

catch

(Exception e){e.printStackTrace();}

        start.setOnClickListener(

new

 OnClickListener() {

            @Override

public

void

 onClick(View v) {

                mp.start();     }     });

pause.setOnClickListener(

new

 OnClickListener() {

            @Override

public

void

 onClick(View v) {

                mp.pause();

            }

        });

        stop.setOnClickListener(

new

 OnClickListener() {

            @Override

public

void

 onClick(View v) {

                mp.stop();

            }

        });

    }

}

•

By the help of 

MediaController

 and 

VideoView

 classes,

we can play the video files in android.

•

MediaController class

The 

android.widget.MediaController

 is a view that

contains media controls like play/pause, previous, next,

fast-forward, rewind etc.

•

VideoView class

The 

android.widget.VideoView

 class provides methods

to play and control the video player. The commonly

used methods of VideoView class are as follows:

Android Video Player

activity_main.xml

<RelativeLayout

 xmlns:androclass="http://schemas.android.co

m/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" 

>

<VideoView

        android:id="@+id/videoView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_centerVertical="true" 

/>

</RelativeLayout>

Activity class

•

Let's write the code of to play the video file. Here, we are going to play 1.mp4 file located

inside the sdcard/media directory.

package

 com.example.video1;

import

 android.net.Uri;

import

 android.os.Bundle;

import

 android.app.Activity;

import

 android.view.Menu;

import

 android.widget.MediaController;

import

 android.widget.VideoView;

public

class

 MainActivity 

extends

 Activity {

    @Override

protected

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

VideoView videoView =(VideoView)findViewById(R.id.videoView1);

                //Creating MediaController

        MediaController mediaController= 

new

 MediaController(

this

);

            mediaController.setAnchorView(videoView);

              //specify the location of media file

           Uri uri=Uri.parse(Environment.getExternalStorageDirectory().getPath

()+"/media/1.mp4");

              //Setting MediaController and URI, then starting the videoView

           videoView.setMediaController(mediaController);

           videoView.setVideoURI(uri);

           videoView.requestFocus();

           videoView.start();

    }  @Override

public

boolean

 onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.activity_main, menu);

return

true

;  }  }

Android Media Recorder

•

MediaRecorder

 class can be used to record

audio and video files.

•

After recording the media, we can create a

sound file that can be played later.

•

activity_main.xml

–

Drag 2 buttons from the palette, one to start the

recording and another stop the recording. Here,

we are registering the view with the listener in xml

file using 

android:onClick

.

<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

     <Button    android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentTop="true"

        android:layout_marginLeft="68dp"

        android:layout_marginTop="50dp"

        android:text="Start Recording"

        android:onClick="startRecording"   />

      <Button    android:id="@+id/button2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@+id/button1"

        android:layout_below="@+id/button1"

        android:layout_marginTop="64dp"

        android:text="Stop Recording"

        android:onClick="stopRecording"   />

</RelativeLayout>

package

 com.javatpoint.mediarecorder;

import

 java.io.File;

import

 java.io.IOException;

import

 android.app.Activity;

import

 android.content.ContentResolver;

import

 android.content.ContentValues;

import

 android.content.Intent;

import

 android.media.MediaRecorder;

import

 android.net.Uri;

import

 android.os.Bundle;

import

 android.os.Environment;

import

 android.provider.MediaStore;

import

 android.util.Log;

import

 android.view.View;

import

 android.widget.Button;

import

 android.widget.Toast;

public

class

 MainActivity 

extends

 Activity {

      MediaRecorder recorder;

      File audiofile = 

null

;

static

final

 String TAG = "MediaRecording";

      Button startButton,stopButton;

 @Override

public

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        startButton = (Button) findViewById(R.id.button1);

        stopButton = (Button) findViewById(R.id.button2);     }

public

void

 startRecording(View view) 

throws

 IOException {

        startButton.setEnabled(

false

);

        stopButton.setEnabled(

true

);     //Creating file

        File dir = Environment.getExternalStorageDirectory();

try

 {

          audiofile = File.createTempFile("sound", ".3gp", dir);

        } 

catch

 (IOException e) {

          Log.e(TAG, "external storage access error");

return

;

        }   //Creating MediaRecorder and specifying audio source, output format, encoder & output format

        recorder = 

new

 MediaRecorder();

        recorder.setAudioSource(MediaRecorder.AudioSource.MIC);

        recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);

        recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

        recorder.setOutputFile(audiofile.getAbsolutePath());

        recorder.prepare();

        recorder.start();  }

public void stopRecording(View view) {

        startButton.setEnabled(true);

        stopButton.setEnabled(false);

            //stopping recorder

        recorder.stop();

        recorder.release();

           //after stopping the recorder, create the sound file and add it to media library.

        addRecordingToMediaLibrary();

      }

      protected void addRecordingToMediaLibrary() {

            //creating content values of size 4

        ContentValues values = new ContentValues(4);

        long current = System.currentTimeMillis();

        values.put(MediaStore.Audio.Media.TITLE, "audio" + audiofile.getName());

        values.put(MediaStore.Audio.Media.DATE_ADDED, (int) (current / 1000));

        values.put(MediaStore.Audio.Media.MIME_TYPE, "audio/3gpp");

        values.put(MediaStore.Audio.Media.DATA, audiofile.getAbsolutePath());

             //creating content resolver and storing it in the external content uri

        ContentResolver contentResolver = getContentResolver();

        Uri base = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;

        Uri newUri = contentResolver.insert(base, values);

           //sending broadcast message to scan the media file so that it can be available

        sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, newUri));

        Toast.makeText(this, "Added File " + newUri, Toast.LENGTH_LONG).show();

      }

    }

Android Text To Speech

•

In android, you can convert your text into speech

by the help of 

TextToSpeech

 class. After

completion of the conversion, you can playback

or create the sound file.

•

Constructor of TextToSpeech class

–

TextToSpeech(Context

context,TextToSpeech.OnInitListener)

Methods of TextToSpeech class

TextToSpeech.OnInitListener Interface

•

You need to implement

TextToSpeech.OnInitListener interface, for

performing event handling on TextToSpeech

engine.

•

Method of TextToSpeech.OnInitListener

Interface

–

There is only one method in this interface

activity_main.xml

<RelativeLayout

 xmlns:androclass="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" 

>

<EditText

    android:id="@+id/editText1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentTop="true"

        android:layout_marginLeft="77dp"

        android:layout_marginTop="42dp"

        android:ems="10" 

>

<requestFocus

/>

</EditText>

<Button

      android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@+id/editText1"

        android:layout_below="@+id/editText1"

        android:layout_marginLeft="59dp"

        android:layout_marginTop="39dp"

        android:text="Speak" 

/>

<TextView

    android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignBaseline="@+id/editText1"

        android:layout_alignBottom="@+id/editText1"

        android:layout_alignParentLeft="true"

        android:text="Enter Text:" 

/>

</RelativeLayout>

 MainActivity.java

package

 com.example.texttospeech;

import

 android.os.Bundle;

import

 android.app.Activity;

import

 android.view.Menu;

import

 java.util.Locale;

import

 android.app.Activity;

import

 android.os.Bundle;

import

 android.speech.tts.TextToSpeech;

import

 android.util.Log;

import

 android.view.View;

import

 android.widget.Button;

import

 android.widget.EditText;

public

class

 MainActivity 

extends

 Activity 

implements

TextToSpeech.OnInitListener {

/** Called when the activity is first created. */

private

 TextToSpeech tts;

private

 Button buttonSpeak;

private

 EditText editText;

@Override

public

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

tts = 

new

 TextToSpeech(

this

, 

this

);

buttonSpeak = (Button) findViewById(R.id.button1);

editText = (EditText) findViewById(R.id.editText1);

buttonSpeak.setOnClickListener(

new

 View.OnClickListener() {

    @Override

public

void

 onClick(View arg0) {

        speakOut();

    }

});

}

@Override

public void onDestroy() {

// Don't forget to shutdown tts!

if (tts != null) {

    tts.stop();

    tts.shutdown();

}

super.onDestroy();

}

@Override

public void onInit(int status) {

if (status == TextToSpeech.SUCCESS) {

    int result = tts.setLanguage(Locale.US);

    if (result == TextToSpeech.LANG_MISSING_DATA|| result == TextToSpeech.LANG_NOT_S

UPPORTED) {

        Log.e("TTS", "This Language is not supported");

    } else {

        buttonSpeak.setEnabled(true);

        speakOut();

    }

} else {

    Log.e("TTS", "Initilization Failed!");

}

}

private void speakOut() {

String text = editText.getText().toString();

tts.speak(text, TextToSpeech.QUEUE_FLUSH, null);

}

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.activity_main, menu);

        return true;

    }

}

Android Sensor

•

Sensors

 can be used to monitor the three-

dimensional device movement or change in

the environment of the device.

•

Android provides sensor api to work with

different types of sensors.

Types of Sensors

Android supports three types of sensors:

•

The Android sensor framework provided a following classes and interfaces

to access device sensors and acquire raw sensor data.

•

Android provides SensorManager and Sensor classes to use the sensors in

our application. In order to use sensors, first thing you need to do is to

instantiate the object of SensorManager class. It can be achieved as follows.

SensorManager sMgr;

sMgr = (SensorManager)this.getSystemService(SENSOR_SERVICE);

•

The next thing you need to do is to instantiate the object of Sensor class by

calling the getDefaultSensor() method of the SensorManager class.

Its syntax is given below −

Sensor light;

light=sMgr.getDefaultSensor(Sensor.TYPE_LIGHT);

•

Once that sensor is declared , you need to register its listener and override

two methods which are onAccuracyChanged and onSensorChanged. Its

syntax is as follows −

sMgr.registerListener(this,light,SensorManager.SENSOR_DELAY_NORMAL);

public void onAccuracyChanged(Sensor sensor, int accuracy) { }

public void onSensorChanged(SensorEvent event) { }

•

Getting list of sensors supported

–

You can get a list of sensors supported by your device

by calling the getSensorList method, which will return a

list of sensors containing their name and version

number and much more information. You can then

iterate the list to get the information. Its syntax is given

below −

sMgr=(SensorManager)this.getSystemService(SENSOR_SERVICE

);

List<Sensor> list = sMgr.getSensorList(Sensor.TYPE_ALL);

for(Sensor sensor: list){ }

•

Apart from the these methods, there are other methods

provided by the SensorManager class for managing

sensors framework. These methods are listed below −

activity_main.xml

(List of sensors supported by mobile)

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/

android"

android:orientation="vertical" android:layout_width="match_parent

"

android:layout_height="match_parent"

android:paddingLeft="10dp"

android:paddingRight="10dp">

<TextView

    android:id="@+id/sensorslist"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:layout_marginTop="80dp"

    android:text="Sensors"

    android:textSize="20dp"

    android:textStyle="bold"

    android:layout_gravity="center"

    android:visibility="gone"/>

</LinearLayout>

MainActivity.java

import android.hardware.Sensor;

import android.hardware.SensorManager;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.TextView;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private SensorManager mgr;

    private TextView txtList;   @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        mgr = (SensorManager)getSystemService(Context.SENSOR_SERVICE);

        txtList = (TextView)findViewById(R.id.sensorslist);

        List<Sensor> sensorList = mgr.getSensorList(Sensor.TYPE_ALL);

        StringBuilder strBuilder = new StringBuilder();

        for(Sensor s: sensorList){

            strBuilder.append(s.getName()+"\n");

        }     txtList.setVisibility(View.VISIBLE);

        txtList.setText(strBuilder);   }  }

Changed background color

when device is shuffled

 activity_main.xml

<RelativeLayout

 xmlns:android="http://schemas.android.com/apk/res/androi

d"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" 

>

<TextView

        android:id="@+id/textView"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:text="Shake to switch color" 

/>

</RelativeLayout>

import

 android.app.Activity;

import

 android.graphics.Color;

import

 android.hardware.Sensor;

import

 android.hardware.SensorEvent;

import

 android.hardware.SensorEventListener;

import

 android.hardware.SensorManager;

import

 android.os.Bundle;

import

 android.view.View;

import

 android.widget.Toast;

public

class

 MainActivity 

extends

 Activity 

implements

 SensorEventList

ener{

private

 SensorManager sensorManager;

private

boolean

 isColor = 

false

;

private

 View view;

private

long

 lastUpdate;

 @Override

public

void

 onCreate(Bundle savedInstanceState) {

super

.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        view = findViewById(R.id.textView);

        view.setBackgroundColor(Color.GREEN);

        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);

        lastUpdate = System.currentTimeMillis();

      }

      //overriding two methods of SensorEventListener

      @Override

public

void

 onAccuracyChanged(Sensor sensor, 

int

 accuracy) {}

      @Override

public

void

 onSensorChanged(SensorEvent event) {

if

 (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

          getAccelerometer(event);

        }

      }

private

void

 getAccelerometer(SensorEvent event) {

float

[] values = event.values;

        // Movement

float

 x = values[0];

float

 y = values[1];

float

 z = values[2];

float

 accelationSquareRoot = (x * x + y * y + z * z)

            / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH);

long

 actualTime = System.currentTimeMillis();

        Toast.makeText(getApplicationContext(),String.valueOf(accelationSquareRoot)+" "+

                    SensorManager.GRAVITY_EARTH,Toast.LENGTH_SHORT).show();

if

 (accelationSquareRoot >= 2) //it will be executed if you shuffle

        {    

if

 (actualTime - lastUpdate < 200) {

return

;

          }

          lastUpdate = actualTime;//updating lastUpdate for next shuffle

if

 (isColor) {

            view.setBackgroundColor(Color.GREEN);

          } 

else

 {

            view.setBackgroundColor(Color.RED);

          }

          isColor = !isColor;     }    }

  @Override

protected

void

 onResume() {

super

.onResume();

        // register this class as a listener for the orientation and

        // accelerometer sensors

        sensorManager.registerListener(

this

,sensorManager.getDefaultSe

nsor(Sensor.TYPE_ACCELEROMETER),

                                    SensorManager.SENSOR_DELAY_NORMAL);

      }

      @Override

protected

void

 onPause() {

        // unregister listener

super

.onPause();

        sensorManager.unregisterListener(

this

);

      }

    }

Android Camera

•

Camera

 is mainly used to capture picture and

video. We can control the camera by using

methods of camera API.

•

Android provides the facility to work on camera by

2 ways:

–

By Camera Intent

–

By Camera API

Using existing android camera application

in our application

•

You will use MediaStore.ACTION_IMAGE_CAPTURE to launch an

existing camera application installed on your phone. Its syntax is

given below:-

Intent intent = new

Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);

•

Now you will use the function

startActivityForResult()

 to launch this activity and wait

for its result. Its syntax is given below

startActivityForResult(intent,0);

This method has been defined in the 

activity

 class.

We are calling it from main activity. There are

methods defined in the activity class that does the

same job , but used when you are not calling from the

activity but from somewhere else.

Using Camera By using Camera Api

•

This class is used for controlling device cameras. It can

be used to take pictures when you are building a

camera application.

Camera API works in following ways:

1.

Camera Manager

: This is used to get all the cameras

available in the device like front camera back camera

each having the camera id.

2.

CameraDevice

: You can get it from Camera Manager

class by its id.

3.

CaptureRequest

: You can create a capture request from

camera device to capture images.

4.

CameraCaptureSession

: To get capture request’s from

Camera Device create a CameraCaptureSession.

5.

CameraCaptureSession.CaptureCallback

: This is going

to provide the Capture session results.

Checking Camera Permissions:

•

For the first we have used the Function

requestPermissions(new

String[]{Manifest.permission.CAMERA},MY_CAMERA_PERMIS

SION_CODE);

We will check whether the user has given permissions or

not if not then first we will ask the user for permissions if a

user is using Android version above Android Marshmallow(API

23) because From Android Marshmallow(API 23) and above by

default all dangerous permission disabled. When the App

opens for the first time after installation then you have to

grant permissions. But if the android version is below

Marshmallow then this function won’t be called.

requestPermissions(newString[]{Manifest.permission.CAMERA},

MY_CAMERA_PERMISSION_CODE)

•

startActivityForResult(cameraIntent, CAMERA_REQUEST)

Method:

Now we will call Function startActivityForResult(cameraIntent, CAMERA_REQUEST);

When you start an activity for the result, it request Camera to take a photo then

return it to your calling activity, you pass it a unique integer value or anything you

have not used already in that class. The requestCode helps you to identify from

which 

Intent

 you came back.

So, that CAMERA_REQUEST could be any value you define in your class like this:

private static final int CAMERA_REQUEST = 1888

@Override

public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data)

{

 if (requestCode == CAMERA_REQUEST && resultCode == Activity.RESULT_OK) {

 theImage = (Bitmap) data.getExtras().get("data");

photo=getEncodedString(theImage); setDataToDataBase();

}

 }

•

getEncodedString(Bitmap bitmap) Method:

Since now I am able to click an image from the camera but that

image is in the form of Bitmap but I want to store it as a string in

the database, so I am going to encode it using

ByteArrayOutputStream Class. This Class holds a copy of data and

forwards it to multiple streams.

private String getEncodedString(Bitmap bitmap)

{

ByteArrayOutputStream os = new ByteArrayOutputStream();

bitmap.compress(Bitmap.CompressFormat.JPEG,100, os);

/* or use below if you want 32 bit images

bitmap.compress(Bitmap.CompressFormat.PNG, 100, os);*/

byte[] imageArr = os.toByteArray();

return Base64.encodeToString(imageArr, Base64.URL_SAFE);

}

•

setDataToDataBase() Method:

Now I am storing data(Image) to a database(here I have used SQLite). Here the

ContentValue class helps to put information inside an object in the form of Key-

Value pairs for columns. To Insert or Update your WritableDatabase The object can

then be passed to an instance of the SQLiteDatabase class.

private void setDataToDataBase()

{

db = databaseHandler.getWritableDatabase(); ContentValues cv = new

ContentValues(); cv.put(databaseHandler.KEY_IMG_URL,photo);

 long id = db.insert(databaseHandler.TABLE_NAME, null, cv);

 if (id < 0)

 {

Toast.makeText(getContext(), "Something went wrong. Please try again later...",

Toast.LENGTH_LONG).show();

}

 else

 {

Toast.makeText(getContext(), "Add successful", Toast.LENGTH_LONG).show();

 }

}

•

Please add CAMERA permission inside your

AndroidManifest.xml file .

<uses-permission

android:name="android.permission.CAMERA" />

•

Eg.camera image inside image view as follow:

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/activity_main" android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.android_examples.captureimagecamera_android_examplescom.M

ainActivity"

android:orientation="vertical" android:background="#FFF9C4">

 <ImageView  android:layout_width="fill_parent"

android:layout_height="300dp"

android:layout_centerHorizontal="true“

 android:id="@+id/imageView" />

<Button android:text="Click here to capture image using camera"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/button" />

</LinearLayout>

import android.Manifest;

import android.content.Intent;

import android.content.pm.PackageManager;

import android.graphics.Bitmap;

 import android.support.v4.app.ActivityCompat;

 import android.support.v7.app.AppCompatActivity;

 import android.os.Bundle;

 import android.view.View;

 import android.widget.Button;

 import android.widget.ImageView;

 import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

Button button ;

ImageView imageView ;

Intent intent ;

public static final int RequestPermissionCode = 1 ;

@Override

protected void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

button = (Button)findViewById(R.id.button);

imageView =(ImageView)findViewById(R.id.imageView);

EnableRuntimePermission(); button.setOnClickListener(new

View.OnClickListener()

{

@Override

public void onClick(View view) {

 intent = new

Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);

startActivityForResult(intent, 7);

 }

});

}

protected void onActivityResult(int requestCode, int resultCode, Intent data)

{

 if (requestCode == 7 && resultCode == RESULT_OK)

 {

 Bitmap bitmap = (Bitmap)data.getExtras().get("data");

imageView.setImageBitmap(bitmap);

}

}

public void EnableRuntimePermission()

{

if(ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,

Manifest.permission.CAMERA))

{

Toast.makeText(MainActivity.this,"CAMERA permission allows us to Access CAMERA

app", Toast.LENGTH_LONG).show();

}

else

 {

ActivityCompat.requestPermissions(MainActivity.this,new String[] {

Manifest.permission.CAMERA}, RequestPermissionCode);

}

 }

@Override

public void onRequestPermissionsResult(int RC, String per[], int[]

PResult)

 {

switch (RC)

{

case RequestPermissionCode:

 if (PResult.length > 0 && PResult[0] ==

PackageManager.PERMISSION_GRANTED)

{

Toast.makeText(MainActivity.this,"Permission Granted, Now your

application can access CAMERA.", Toast.LENGTH_LONG).show();

} else

{

Toast.makeText(MainActivity.this,"Permission Canceled, Now your

application cannot access CAMERA.", Toast.LENGTH_LONG).show(); }

break;

 }

 }

 }

Camera Video Capture And Save On

SDCard

•

XML FILE : AndroidManifest.xml

•

To access external storage(SDCARD).

<uses-permission

android:name="android.permission.WRITE_EXTERNAL_STO

RAGE" />

    <uses-permission

android:name="android.permission.RECORD_AUDIO" />

        <!-- We will request access to the camera, saying we

require a camera

         of some sort but not one with autofocus capability. -->

    <uses-permission

android:name="android.permission.CAMERA" />

    <uses-feature android:name="android.hardware.camera"

/>

XML FILE : main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout

xmlns:android="

http://schemas.android.com/apk/res/android

"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent >

      <Button

            android:id="@+id/recording"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="Capture Video"/>

   <TextView

    android:id="@+id/output"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="@string/hello"/>

</LinearLayout>

import java.io.File;

import java.text.SimpleDateFormat;

import android.app.Activity;

import android.content.Intent;

import android.net.Uri;

import android.os.Bundle;

import android.os.Environment;

import android.provider.MediaStore;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

public class VideocameraActivity extends Activity {

    private Uri fileUri;

    public static final int MEDIA_TYPE_VIDEO = 2;

    private static final int CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE = 200;

    public static VideocameraActivity ActivityContext =null;

    public static TextView output;

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

 ActivityContext = this;

         Button buttonRecording = (Button)findViewById(R.id.recording);

        output = (TextView)findViewById(R.id.output);

           buttonRecording.setOnClickListener(new Button.OnClickListener(){

            @Override

            public void onClick(View arg0)

{

                 // create new Intentwith with Standard Intent action that can be sent to have the

camera application capture an video and return it.

                Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);

                // create a file to save the video

                fileUri = getOutputMediaFileUri(MEDIA_TYPE_VIDEO);

                // set the image file name

                intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

                // set the video image quality to high

                intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);

                // start the Video Capture Intent

                startActivityForResult(intent, CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE);

            }});

    }

/** Create a file Uri for saving an image or video */

    private static Uri getOutputMediaFileUri(int type){

          return Uri.fromFile(getOutputMediaFile(type));

    }

    /** Create a File for saving an image or video */

    private static File getOutputMediaFile(int type){

        // Check that the SDCard is mounted

        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(

                  Environment.DIRECTORY_PICTURES), "MyCameraVideo");

        // Create the storage directory(MyCameraVideo) if it does not exist

        if (! mediaStorageDir.exists()){

            if (! mediaStorageDir.mkdirs()){

                output.setText("Failed to create directory MyCameraVideo.");

                Toast.makeText(ActivityContext, "Failed to create directory MyCameraVideo.",

                        Toast.LENGTH_LONG).show();

                Log.d("MyCameraVideo", "Failed to create directory MyCameraVideo.");

                return null;

            }

        }

// Create a media file name

        // For unique file name appending current timeStamp with file name

        java.util.Date date= new java.util.Date();

        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")

                             .format(date.getTime());

        File mediaFile;

        if(type == MEDIA_TYPE_VIDEO) {

            // For unique video file name appending current timeStamp with file name

            mediaFile = new File(mediaStorageDir.getPath() + File.separator +

            "VID_"+ timeStamp + ".mp4");

        } else {

            return null;

        }

        return mediaFile;

    }

@Override

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        // After camera screen this code will excuted

        if (requestCode == CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE) {

            if (resultCode == RESULT_OK) {

                output.setText("Video File : " +data.getData());

                // Video captured and saved to fileUri specified in the Intent

                Toast.makeText(this, "Video saved to:" + data.getData(), Toast.LENGTH_LONG).show();

            } else if (resultCode == RESULT_CANCELED) {

                output.setText("User cancelled the video capture.");

                // User cancelled the video capture

                Toast.makeText(this, "User cancelled the video capture.",

                        Toast.LENGTH_LONG).show();

            } else {

                output.setText("Video capture failed.");

                // Video capture failed, advise user

                Toast.makeText(this, "Video capture failed.",

                        Toast.LENGTH_LONG).show();

            }

        }

    }

}

Bluetooth

•

Bluetooth is a way to send or receive data

between two different devices. Android platform

includes support for the Bluetooth framework

that allows a device to wirelessly exchange data

with other Bluetooth devices.

•

Android provides Bluetooth API to perform these

different operations.

–

Scan for other Bluetooth devices

–

Get a list of paired devices

–

Connect to other devices through service discovery

Android Bluetooth API

The android.bluetooth package provides a lot of interfaces classes to

work with bluetooth such as:

•

BluetoothAdapter

•

BluetoothDevice

•

BluetoothSocket

•

BluetoothServerSocket

•

BluetoothClass

•

BluetoothProfile

•

BluetoothProfile.ServiceListener

•

BluetoothHeadset

•

BluetoothA2dp

•

BluetoothHealth

•

BluetoothHealthCallback

•

BluetoothHealthAppConfiguration

BluetoothAdapter class

•

By the help of BluetoothAdapter class, we can perform

fundamental tasks such as initiate device discovery, query a

list of paired (bonded) devices, create a

BluetoothServerSocket instance to listen for connection

requests etc.

•

Constants of BluetoothAdapter class

BluetoothAdapter class provides many constants. Some of them

are as follows:

–

String ACTION_REQUEST_ENABLE

–

String ACTION_REQUEST_DISCOVERABLE

–

String ACTION_DISCOVERY_STARTED

–

String ACTION_DISCOVERY_FINISHED

Methods of BluetoothAdapter class

•

static synchronized BluetoothAdapter getDefaultAdapter()

 returns

the instance of BluetoothAdapter.

•

boolean enable()

 enables the bluetooth adapter if it is disabled.

•

boolean isEnabled()

 returns true if the bluetooth adapter is

enabled.

•

boolean disable()

 disables the bluetooth adapter if it is enabled.

•

String getName()

 returns the name of the bluetooth adapter.

•

boolean setName(String name)

 changes the bluetooth name.

•

int getState()

 returns the current state of the local bluetooth

adapter.

•

Set<BluetoothDevice> getBondedDevices()

 returns a set of paired

(bonded) BluetoothDevice objects.

•

boolean startDiscovery()

 starts the discovery process.

Android Set Bluetooth Permissions

•

To use Bluetooth features in our android applications,

we must need to add multiple permissions, such

as 

BLUETOOTH

 and 

ACCESS_COARSE_LOCATION

 or 

ACC

ESS_FINE_LOCATION

 in our manifest file.

•

In case, if we want to discover the available Bluetooth

devices or manipulate Bluetooth settings from our app,

we need to define 

BLUETOOTH_ADMIN

 permission.

<manifest ... >

<uses-

permission android:name="android.permission.BLUET

OOTH"/>

<uses-

permission android:name="android.permission.BLUET

OOTH_ADMIN"/>

<uses-

permission android:name="android.permission.ACCESS

_COARSE_LOCATION"/>

...

</manifest>

Android BluetoothAdapter Class

In android, we can perform Bluetooth related activities by using 

BluetoothAdapter

 class in our

applications.

By using 

BluetoothAdapter

 object, we can interact with device’s Bluetooth adapter to perform

Bluetooth related operations. In case, if device does not contain any Bluetooth adapter, then it will

return null.

Following is the code snippet to initialize 

BluetoothAdapter

 class and to know whether the Bluetooth is

supported on the device or not.

BluetoothAdapter bAdapter = BluetoothAdapter.getDefaultAdapter();

if(bAdapter==null)

{

    // Device won't support Bluetooth

}

If you observe above code snippet, we used 

getDefaultAdapter()

 method of 

BluetoothAdapter

 class,

which will return whether the device contains Bluetooth adapter or not.

In case if 

getDefaultAdapter()

 method returns NULL, then the device does not support Bluetooth and

we can disable all Bluetooth features.

Android Enable or Disable Bluetooth

If Bluetooth is supported but disabled, then 

isEnabled()

 method will return 

false

 and

we can request user to enable Bluetooth without leaving our application by

using 

startActivityForResult()

 method with 

ACTION_REQUEST_ENABLE

 intent

action parameter.

Following is the code snippet to enable a Bluetooth by

using 

BluetoothAdapter

 parameter 

ACTION_REQUEST_ENABLE

.

if(!bAdapter.isEnabled())

{

    Intent eintent = new Intent(BluetoothAdapter.ACTION_REQUEST_

ENABLE);

    startActivityForResult(eintent, intVal);

}

If you observe above code snippet, we used 

startActivityForResult()

 method

with 

ACTION_REQUEST_ENABLE

intent

 action parameter to enable a

Bluetooth.

The second parameter 

intVal

 in 

startActivityForResult()

 method is a locally

defined integer that must be greater than 

0

 and the system will return this

parameter back to us during 

onActivityResult()

 implementation as

a 

requestCode

 parameter.

Android Enable Discoverability

To make the device discoverable to other devices, we need to start the

new 

activity

 by calling 

startActivityForResult(intent, int)

 with

the  

ACTION_REQUEST_DISCOVERABLE

intent

.

Following is the code snippet to enable the system’s discoverable mode to make

sure that the device discoverable to other devices.

Intent dIntent =  new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);

dIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);

startActivity(dIntent);

If you observe above code snippet, we are making sure our device discoverable to

other devices using 

ACTION_REQUEST_DISCOVERABLE

. By default, the device

becomes discoverable for 120 seconds. We can extend the device discoverable

duration up to 3600 seconds (1 hour), by adding

the 

EXTRA_DISCOVERABLE_DURATION

 extra.

Android List Paired Devices

By using 

BluetoothAdapter

 method 

getBondedDevices()

, we can get the

Bluetooth paired devices list.

Following is the code snippet to get all paired devices with name and MAC

address of each device.

// Get paired devices.

Set<BluetoothDevice> pairedDevices = bAdapter.getBondedDevices();

if (pairedDevices.size() > 0) {

    // There are paired devices. Get the name and address of each paired d

evice.

    for (BluetoothDevice device : pairedDevices) {

        String deviceName = device.getName();

        String deviceHardwareAddress = device.getAddress(); // MAC address

    }

}

If you observe above code, we are getting the Bluetooth paired devices name

and mac address by using 

BluetoothDevice

 object.

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout

xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

android:paddingBottom="@dimen/activity_vertical_margin"

tools:context=".MainActivity" android:transitionGroup="true">

<TextView android:text="Bluetooth Example"

android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/textview"

android:textSize="35dp" android:layout_alignParentTop="true"

android:layout_centerHorizontal="true" />

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="Tutorials point"

android:id="@+id/textView" android:layout_below="@+id/textview"

android:layout_centerHorizontal="true" android:textColor="#ff7aff24"

android:textSize="35dp" />

<ImageView android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:id="@+id/imageView" android:src="@drawable/abc"

android:layout_below="@+id/textView"

android:layout_centerHorizontal="true"

android:theme="@style/Base.TextAppearance.AppCompat" />

<Button android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="Turn On"

android:id="@+id/button"

android:layout_below="@+id/imageView"

android:layout_toStartOf="@+id/imageView"

android:layout_toLeftOf="@+id/imageView"

android:clickable="true" android:onClick="on" />

<Button android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="Get visible"

android:onClick="visible" android:id="@+id/button2"

android:layout_alignBottom="@+id/button"

android:layout_centerHorizontal="true" />

<Button android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="List devices"

android:onClick="list" android:id="@+id/button3"

android:layout_below="@+id/imageView"

android:layout_toRightOf="@+id/imageView"

android:layout_toEndOf="@+id/imageView" />

 <Button android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="turn off"

android:onClick="off" android:id="@+id/button4"

android:layout_below="@+id/button" android:layout_alignParentLeft="true"

android:layout_alignParentStart="true" />

<ListView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/listView"

android:layout_alignParentBottom="true"

android:layout_alignLeft="@+id/button" android:layout_alignStart="@+id/button"

android:layout_below="@+id/textView2" />

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="Paired devices:"

android:id="@+id/textView2" android:textColor="#ff34ff06"

android:textSize="25dp" android:layout_below="@+id/button4"

android:layout_alignLeft="@+id/listView"

android:layout_alignStart="@+id/listView" />

 </RelativeLayout>

import android.app.Activity;

import android.bluetooth.BluetoothAdapter;

import android.bluetooth.BluetoothDevice;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.ArrayAdapter;

import android.widget.Button;

import android.widget.ListView;

import android.widget.Toast;

import java.util.ArrayList; import java.util.Set;

public class MainActivity extends Activity {

Button b1,b2,b3,b4;

private BluetoothAdapter BA;

private Set<BluetoothDevice>pairedDevices;

ListView lv;

@Override

protected void onCreate(Bundle savedInstanceState)

 {

 super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

b1 = (Button) findViewById(R.id.button); b2=(Button)findViewById(R.id.button2);

b3=(Button)findViewById(R.id.button3); b4=(Button)findViewById(R.id.button4);

 BA = BluetoothAdapter.getDefaultAdapter();

lv = (ListView)findViewById(R.id.listView);

 }

public void on(View v)

{

 if (!BA.isEnabled())

{

Intent turnOn = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);

startActivityForResult(turnOn, 0); Toast.makeText(getApplicationContext(), "Turned

on",Toast.LENGTH_LONG).show();

}

 else

 {

 Toast.makeText(getApplicationContext(), "Already on", Toast.LENGTH_LONG).show();

}

}

public void off(View v)

{

 BA.disable();

 Toast.makeText(getApplicationContext(), "Turned off" ,Toast.LENGTH_LONG).show();

}

public void visible(View v)

{

 Intent getVisible = new

Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);

startActivityForResult(getVisible, 0);

}

public void list(View v)

{

pairedDevices = BA.getBondedDevices();

ArrayList list = new ArrayList();

for(BluetoothDevice bt : pairedDevices)

list.add(bt.getName());

Toast.makeText(getApplicationContext(), "Showing Paired

Devices",Toast.LENGTH_SHORT).show();

final ArrayAdapter adapter = new

ArrayAdapter(this,android.R.layout.simple_list_item_1, list);

lv.setAdapter(adapter);

}

 }

Animation

•

Animation is the process of creating motion and shape change

•

 It define the properties of our Views that should be animated using

a technique called Tween Animation.It take the following

parameters i.e. size, time duration , rotation angle, start value , end

value, and perform the required animation on that object.You

can  execute the animation by specifying transformations on your

View. This can be done in XML resource files or programmatically.

•

Android View animation can make animation on any View objects,

such as ImageView, TextView or Button objects. View animation can

only animate simple properties like position, size, rotation, and the

alpha property that allows you animate the transparency of a View.

•

The drawback of this mechanism is that it can only be applied to

Views.

Property Animation:

•

This animation was introduced in Android 3.0 (API level 11). It

allows the user to animate anything.

•

Property animations are highly customizable, you can specify the

duration, the number of repeats, the type of interpolation, and

the frame rate of the animation. The Property Animation system

is always preferred for more complex animations.

•

Property animations allow us to animate any property of any

object from one value to another over a specified duration.

Drawable Animation:

•

This animation allows the user to load drawable resources and

display them one frame after another. This method of animation is

useful when user wants to animate things that are easier to

represent with Drawable resources.

•

To use Animations in Android , Android has provided us a class

called Animation.

•

To perform animation in android , we will  call a static

function 

loadAnimation()

(this method is used to load animation) of

the class 

AnimationUtils.

 We are going to receive the result in an

instance of Animation Object. Its syntax is as follows −

•

Animation animation

=AnimationUtils.loadAnimation(getApplicationContext(),

R.anim.myanimation);

•

Second parameter refers to our animation.xml file.It is created

under res directory

(res->anim->myanimation.xml)

•

The Animation class has many methods given

below:

1.

start(): 

This method will start the animation.

2.

setDuration(long duration): 

This method sets the

duration of an animation.

3.

getDuration()

: This method gets the duration.

4.

end():

 This method ends the animation.

5.

cancel()

: This method cancels the animation.

Setting The Animation Listeners

(Optional)

Animation listeners can be set by implementing AnimationListener in

our Activity.

 If you will use AnimationListener, then  you  will have to override

following methods.

onAnimationStart

 –

@Override public void onAnimationStart(Animation animation) { }

onAnimationEnd 

–

@Override public void onAnimationEnd(Animation animation) { }

onAnimationRepeat 

–

@Override public void onAnimationRepeat(Animation animation) { }

•

Scale Animation

Scale Animation is used to make a smaller or larger

view either on x axis or y axis. Pivot point can also be

specified around which we want the animation to take

place.

•

Rotate Animation

Rotate Animation is used to rotate a view around a

pivot point by a certain number of degrees.

•

Translate Animation

Translate Animation is used to move a view along the x

or y axis.

•

Alpha Animation

Transparency of a view can be changed by Alpha

Animation

Interpolator:

The dictionary meaning of  Interpolate is to alter, intercept or insert in between two

things or events.

It is used to insert or apply an additional animation effects between the start and the

end value of the property of an object.It is also used to define the rate of change

of an animation.

Types of Interpolator:

1

.Linear Interpolator: 

It is the default interpolator of all animations. It defines that the

rate of the change of the animation is constant.

2.

Accelerate Interpolator:

 Accelerates the moving of the view, it starts out slowly and

then accelerates until it reaches the final position.

3.

Decelerate Interpolator:

 Does the opposite of the accelerate interpolator. It starts

out fast and the slows down.

4.

Accelerate Decelerate Interpolator:

 Makes the moving go slow at the beginning and

the end, but fast in the middle.

5.

Anticipate Interpolator:

 Moves the animation backwards before it starts

6.

Overshoot Interpolator:

 Does the opposite of the anticipate interpolator. It make

the animation to go further than the defined destintion, and then get back to the

defined destination.

7.

Anticipate Overshoot Interpolator: 

 Combines the anticipate and the overshoot

interpoplator. The change starts backward then flings forward and overshoots the

target value and finally goes back to the final value.

8.

Bounce Interpolator:

 Makes an bounce animation before the desired animation

ends.

9.

Cycle Interpolator: 

Repeats the animation for a specified number of cycles.

Important XML Animation Attributes In Android:

1. android:duration:

 The duration in which animation is completed is referred to as

duration attribute. It refers to the ideal duration to show the transition on the

screen.

android:duration="1500“

2. android:fillAfter:

 This attribute defines whether the view should be visible or not

at the end of the animation.We have set its value true in our animation. If it

would set to false then element changes comes to its previous state after the

animation.

android:fillAfter="true“

3. android:interpolator:

 This property refers to the rate of change in animation. You

can define your own interpolators using the time as the constraint. In this

animation we have used an inbuilt interpolator i.e.  linear interpolator.

android:interpolator="@android:anim/linear_interpolator"

4. android:startOffset: 

It refers to  the waiting time before an animation starts.

android:startOffset="2000“

5. android:repeatMode: 

When user wants the animation to be repeated then this

attribute is used

android:repeatMode="restart“

6. android:repeatCount: 

This attribute defines the number of repetitions on

animation.

android:repeatCount="infinite"

Setting the Animation Listeners

•

This is only needed if we wish to listen to events

like start, end or repeat. For this the activity must

implement 

AnimationListener

 and the following

methods need to overridden.

•

onAnimationStart

 : This will be triggered once

the animation started

•

onAnimationEnd

 : This will be triggered once the

animation is over

•

onAnimationRepeat

 : This will be triggered if the

animation repeats

Fade In Animation

fade_in.xml

    <set

xmlns:android="https://schemas.android.com

/apk/res/android" android:fillAfter="true" >

<alpha android:duration="1000"

android:fromAlpha="0.0"

android:interpolator="@android:anim/acceler

ate_interpolator" android:toAlpha="1.0" />

</set>

Here 

alpha

 references the opacity of an object. An object with lower alpha values

is more transparent, while an object with higher alpha values is less transparent,

more opaque. Fade in animation is nothing but increasing alpha value from 0 to 1.

Fade Out Animation

fade_out.xml

<set

xmlns:android="https://schemas.android.com

/apk/res/android" android:fillAfter="true" >

<alpha android:duration="1000"

android:fromAlpha="1.0"

android:interpolator="@android:anim/acceler

ate_interpolator" android:toAlpha="0.0" />

</set>

Fade out android animation is exactly opposite to fade in, where we need to decrease

the alpha value from 1 to 0.

Blink Animation

blink.xml

<set

xmlns:android="https://schemas.android.com/ap

k/res/android"> <alpha android:fromAlpha="0.0"

android:toAlpha="1.0"

android:interpolator="@android:anim/accelerate

_interpolator" android:duration="600"

android:repeatMode="reverse"

android:repeatCount="infinite"/> </set>

Here fade in and fade out are performed infinitely

in reverse mode each time.

Zoom In Animation

zoom_in.xml

<set

xmlns:android="https://schemas.android.com/ap

k/res/android" android:fillAfter="true" > <scale

xmlns:android="https://schemas.android.com/ap

k/res/android" android:duration="1000"

android:fromXScale="1" android:fromYScale="1"

android:pivotX="50%" android:pivotY="50%"

android:toXScale="3" android:toYScale="3" >

</scale> </set>

We use pivotX="50%" and pivotY="50%" to perform

zoom from the center of the element.

Zoom Out Animation

zoom_out.xml

<set

xmlns:android="https://schemas.android.com/ap

k/res/android" android:fillAfter="true" > <scale

xmlns:android="https://schemas.android.com/ap

k/res/android" android:duration="1000"

android:fromXScale="1.0"

android:fromYScale="1.0" android:pivotX="50%"

android:pivotY="50%" android:toXScale="0.5"

android:toYScale="0.5" > </scale> </set>

Rotate Animation

rotate.xml

<set

xmlns:android="https://schemas.android.com/apk/res

/android"> <rotate android:fromDegrees="0"

android:toDegrees="360" android:pivotX="50%"

android:pivotY="50%" android:duration="600"

android:repeatMode="restart"

android:repeatCount="infinite"

android:interpolator="@android:anim/cycle_interpolat

or"/> </set>

A 

from/toDegrees

 tag is used here to specify the degrees

and a cyclic interpolator is used.

Move Animation

move.xml

<set

xmlns:android="https://schemas.android.com

/apk/res/android"

android:interpolator="@android:anim/linear_

interpolator" android:fillAfter="true">

<translate android:fromXDelta="0%p"

android:toXDelta="75%p"

android:duration="800" /> </set>

Slide Up Animation

slide_up.xml

<set

xmlns:android="https://schemas.android.com/apk/res

/android" android:fillAfter="true" > <scale

android:duration="500" android:fromXScale="1.0"

android:fromYScale="1.0"

android:interpolator="@android:anim/linear_interpola

tor" android:toXScale="1.0" android:toYScale="0.0" />

</set>

It’s achieved by

setting 

android:fromYScale=”1.0″

 and 

android:toYScal

e=”0.0″

 inside the 

scale

 tag.

Slide Down Animation

slide_down.xml

<set

xmlns:android="https://schemas.android.com

/apk/res/android" android:fillAfter="true">

<scale android:duration="500"

android:fromXScale="1.0"

android:fromYScale="0.0"

android:toXScale="1.0"

android:toYScale="1.0" /> </set>

Bounce Animation

bounce.xml

<set

xmlns:android="https://schemas.android.com

/apk/res/android" android:fillAfter="true"

android:interpolator="@android:anim/bounc

e_interpolator"> <scale

android:duration="500"

android:fromXScale="1.0"

android:fromYScale="0.0"

android:toXScale="1.0"

android:toYScale="1.0" /> </set>

Sequential Animation

sequential.xml

<set xmlns:android="https://schemas.android.com/apk/res/android"

android:fillAfter="true"

android:interpolator="@android:anim/linear_interpolator" >

 <!-- Move --> <translate android:duration="800" android:fillAfter="true"

android:fromXDelta="0%p" android:startOffset="300" android:toXDelta="75%p"

/> <translate android:duration="800" android:fillAfter="true"

android:fromYDelta="0%p" android:startOffset="1100" android:toYDelta="70%p"

/>

 <translate android:duration="800" android:fillAfter="true"

android:fromXDelta="0%p" android:startOffset="1900" android:toXDelta="-75%p"

/>

 <translate android:duration="800" android:fillAfter="true"

android:fromYDelta="0%p" android:startOffset="2700" android:toYDelta="-70%p"

/>

 <!-- Rotate 360 degrees --> <rotate android:duration="1000"

android:fromDegrees="0"

android:interpolator="@android:anim/cycle_interpolator" android:pivotX="50%"

android:pivotY="50%" android:startOffset="3800" android:repeatCount="infinite"

android:repeatMode="restart" android:toDegrees="360" />

 </set>

Together Animation

together.xml

<set xmlns:android="https://schemas.android.com/apk/res/android"

android:fillAfter="true"

android:interpolator="@android:anim/linear_interpolator" >

<!-- Move -->

<scale xmlns:android="https://schemas.android.com/apk/res/android"

android:duration="4000" android:fromXScale="1"

android:fromYScale="1" android:pivotX="50%"

android:pivotY="50%" android:toXScale="4" android:toYScale="4" >

</scale>

<!-- Rotate 180 degrees -->

<rotate android:duration="500" android:fromDegrees="0"

android:pivotX="50%" android:pivotY="50%"

android:repeatCount="infinite" android:repeatMode="restart"

android:toDegrees="360" />

 </set>

activity_main.xml

<ScrollView xmlns:android="https://schemas.android.com/apk/res/android"

android:layout_width="fill_parent" android:layout_height="fill_parent" >

<RelativeLayout android:layout_width="match_parent"

android:layout_height="match_parent">

<Button android:id="@+id/btnFadeIn" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:text="Fade In" />

 <TextView android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Fade In" android:id="@+id/txt_fade_in"

android:layout_alignBottom="@+id/btnFadeIn"

android:layout_alignLeft="@+id/txt_fade_out"

android:layout_alignStart="@+id/txt_fade_out" />

<Button android:id="@+id/btnFadeOut" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnFadeIn" android:text="Fade Out" />

 <Button android:id="@+id/btnCrossFade" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnFadeOut" android:text="Cross Fade" />

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Cross Fade In" android:id="@+id/txt_out"

android:visibility="gone" android:layout_gravity="center_horizontal"

android:layout_alignTop="@+id/txt_in"

android:layout_alignLeft="@+id/txt_in"

android:layout_alignStart="@+id/txt_in" /> <Button

android:id="@+id/btnBlink" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnCrossFade" android:text="Blink" />

<Button android:id="@+id/btnZoomIn"

android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnBlink" android:text="Zoom In" />

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Blink" android:id="@+id/txt_blink"

android:layout_gravity="center_horizontal"

android:layout_alignBottom="@+id/btnBlink"

android:layout_alignLeft="@+id/txt_zoom_in"

android:layout_alignStart="@+id/txt_zoom_in" />

<Button android:id="@+id/btnZoomOut" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnZoomIn" android:text="Zoom Out" /> <Button

android:id="@+id/btnRotate" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnZoomOut" android:text="Rotate" /> <Button

android:id="@+id/btnMove" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnRotate" android:text="Move" /> <Button

android:id="@+id/btnSlideUp" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnMove" android:text="Slide Up" /> <TextView

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Fade Out" android:id="@+id/txt_fade_out"

android:layout_gravity="center_horizontal"

android:layout_alignBottom="@+id/btnFadeOut"

android:layout_alignLeft="@+id/txt_in" android:layout_alignStart="@+id/txt_in"

/>

<Button android:id="@+id/btnSlideDown" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnSlideUp" android:text="Slide Down" /> <Button

android:id="@+id/btnBounce" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnSlideDown" android:text="Bounce" /> <Button

android:id="@+id/btnSequential" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:layout_margin="5dp"

android:layout_below="@id/btnBounce" android:text="Sequential Animation" />

<Button android:id="@+id/btnTogether" android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_below="@id/btnSequential" android:layout_margin="5dp"

android:text="Together Animation" /> <TextView

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Cross Fade Out" android:id="@+id/txt_in"

android:layout_gravity="center_horizontal"

android:layout_alignBottom="@+id/btnCrossFade"

android:layout_alignLeft="@+id/txt_blink"

android:layout_alignStart="@+id/txt_blink" />

•

<TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium" android:text="Zoom In"

android:id="@+id/txt_zoom_in" android:layout_alignBottom="@+id/btnZoomIn"

android:layout_alignLeft="@+id/txt_zoom_out" android:layout_alignStart="@+id/txt_zoom_out"

/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium" android:text="Zoom Out"

android:id="@+id/txt_zoom_out" android:layout_alignBottom="@+id/btnZoomOut"

android:layout_toRightOf="@+id/btnSequential" android:layout_toEndOf="@+id/btnSequential"

/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium" android:text="Rotate"

android:id="@+id/txt_rotate" android:layout_above="@+id/btnMove"

android:layout_toRightOf="@+id/btnSequential" android:layout_toEndOf="@+id/btnSequential"

/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium" android:text="Move"

android:id="@+id/txt_move" android:layout_alignBottom="@+id/btnMove"

android:layout_alignLeft="@+id/txt_slide_up" android:layout_alignStart="@+id/txt_slide_up" />

<TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium" android:text="Slide Up"

android:id="@+id/txt_slide_up" android:layout_alignBottom="@+id/btnSlideUp"

android:layout_toRightOf="@+id/btnSequential" android:layout_toEndOf="@+id/btnSequential"

/>

•

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Slide Down" android:id="@+id/txt_slide_down"

android:layout_alignBottom="@+id/btnSlideDown"

android:layout_alignLeft="@+id/txt_slide_up"

android:layout_alignStart="@+id/txt_slide_up" /> <TextView

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Bounce" android:id="@+id/txt_bounce"

android:layout_alignBottom="@+id/btnBounce"

android:layout_alignLeft="@+id/txt_slide_down"

android:layout_alignStart="@+id/txt_slide_down" /> <TextView

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Sequential" android:id="@+id/txt_seq"

android:layout_alignBottom="@+id/btnSequential"

android:layout_alignLeft="@+id/txt_bounce"

android:layout_alignStart="@+id/txt_bounce" /> <TextView

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceMedium"

android:text="Together" android:id="@+id/txt_tog"

android:layout_alignBottom="@+id/btnTogether"

android:layout_toRightOf="@+id/btnSequential"

android:layout_toEndOf="@+id/btnSequential" /> </RelativeLayout>

</ScrollView>

•

import android.app.Activity; import android.content.Intent; import

android.os.Bundle; import android.view.View; import

android.view.animation.Animation; import

android.view.animation.AnimationUtils; import

android.widget.Button; import android.widget.TextView; public

class MainActivity extends Activity { Button btnFadeIn, btnFadeOut,

btnCrossFade, btnBlink, btnZoomIn, btnZoomOut, btnRotate,

btnMove, btnSlideUp, btnSlideDown, btnBounce, btnSequential,

btnTogether; Animation

animFadeIn,animFadeOut,animBlink,animZoomIn,animZoomOut,an

imRotate

,animMove,animSlideUp,animSlideDown,animBounce,animSequent

ial,animTogether,animCrossFadeIn,animCrossFadeOut; TextView

txtFadeIn,txtFadeOut,txtBlink,txtZoomIn,txtZoomOut,txtRotate,txt

Move,txtSlideUp,

txtSlideDown,txtBounce,txtSeq,txtTog,txtIn,txtOut; @Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

•

btnFadeIn = (Button) findViewById(R.id.btnFadeIn); btnFadeOut = (Button)

findViewById(R.id.btnFadeOut); btnCrossFade = (Button)

findViewById(R.id.btnCrossFade); btnBlink = (Button) findViewById(R.id.btnBlink);

btnZoomIn = (Button) findViewById(R.id.btnZoomIn); btnZoomOut = (Button)

findViewById(R.id.btnZoomOut); btnRotate = (Button)

findViewById(R.id.btnRotate); btnMove = (Button) findViewById(R.id.btnMove);

btnSlideUp = (Button) findViewById(R.id.btnSlideUp); btnSlideDown = (Button)

findViewById(R.id.btnSlideDown); btnBounce = (Button)

findViewById(R.id.btnBounce); btnSequential = (Button)

findViewById(R.id.btnSequential); btnTogether = (Button)

findViewById(R.id.btnTogether);

txtFadeIn=(TextView)findViewById(R.id.txt_fade_in);

txtFadeOut=(TextView)findViewById(R.id.txt_fade_out);

txtBlink=(TextView)findViewById(R.id.txt_blink);

txtZoomIn=(TextView)findViewById(R.id.txt_zoom_in);

txtZoomOut=(TextView)findViewById(R.id.txt_zoom_out);

txtRotate=(TextView)findViewById(R.id.txt_rotate);

txtMove=(TextView)findViewById(R.id.txt_move);

txtSlideUp=(TextView)findViewById(R.id.txt_slide_up);

txtSlideDown=(TextView)findViewById(R.id.txt_slide_down);

txtBounce=(TextView)findViewById(R.id.txt_bounce);

txtSeq=(TextView)findViewById(R.id.txt_seq);

txtTog=(TextView)findViewById(R.id.txt_tog);

txtIn=(TextView)findViewById(R.id.txt_in);

txtOut=(TextView)findViewById(R.id.txt_out);

•

animFadeIn = AnimationUtils.loadAnimation(getApplicationContext(),

R.anim.fade_in); animFadeIn =

AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_in);

// fade in btnFadeIn.setOnClickListener(new View.OnClickListener() {

@Override public void onClick(View v) {

txtFadeIn.setVisibility(View.VISIBLE);

txtFadeIn.startAnimation(animFadeIn); } }); animFadeOut =

AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_out);

// fade out btnFadeOut.setOnClickListener(new View.OnClickListener() {

@Override public void onClick(View v) {

txtFadeOut.setVisibility(View.VISIBLE);

txtFadeOut.startAnimation(animFadeOut); } });

animCrossFadeIn = AnimationUtils.loadAnimation(getApplicationContext(),

R.anim.fade_in);

animCrossFadeOut = AnimationUtils.loadAnimation(getApplicationContext(),

R.anim.fade_out);

// cross fade btnCrossFade.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

txtOut.setVisibility(View.VISIBLE);

 // start fade in animation

txtOut.startAnimation(animCrossFadeIn);

// start fade out animation

txtIn.startAnimation(animCrossFadeOut);

} });

animBlink = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.blink);

// blink btnBlink.setOnClickListener(new View.OnClickListener()

{ @Override

public void onClick(View v) {

txtBlink.setVisibility(View.VISIBLE);

txtBlink.startAnimation(animBlink); } });

animZoomIn = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.zoom_in); // Zoom In btnZoomIn.setOnClickListener(new

View.OnClickListener() {

 @Override

public void onClick(View v) {

txtZoomIn.setVisibility(View.VISIBLE);

txtZoomIn.startAnimation(animZoomIn);

} });

animZoomOut = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.zoom_out); // Zoom Out

btnZoomOut.setOnClickListener(new View.OnClickListener()

{ @Override public void onClick(View v)

{txtZoomOut.setVisibility(View.VISIBLE);

txtZoomOut.startAnimation(animZoomOut);

} }); animRotate = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.rotate);

// Rotate btnRotate.setOnClickListener(new View.OnClickListener() {

 @Override

public void onClick(View v) {

txtRotate.startAnimation(animRotate); } });

animMove = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.move);

// Move

btnMove.setOnClickListener(new View.OnClickListener()

{

 @Override

public void onClick(View v) {

 txtMove.startAnimation(animMove);

 } });

animSlideUp = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.slide_up);

// Slide Up btnSlideUp.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v)

{

txtSlideUp.startAnimation(animSlideUp);

} });

animSlideDown = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.slide_down);

// Slide Down

btnSlideDown.setOnClickListener(new View.OnClickListener()

{

@Override

public void onClick(View v) {

txtSlideDown.startAnimation(animSlideDown);

} });

animBounce = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.bounce);

// Slide Down btnBounce.setOnClickListener(new View.OnClickListener()

{

@Override

public void onClick(View v) {

txtBounce.startAnimation(animBounce);

} });

animSequential = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.sequential);

// Sequential

btnSequential.setOnClickListener(new View.OnClickListener() {

@Override

 public void onClick(View v) {

txtSeq.startAnimation(animSequential);

 } });

animTogether = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.together);

 // Together

btnTogether.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) { txtTog.startAnimation(animTogether); } }); } }

A sync Task

•

Android UI Main Thread

–

Android handles input events/tasks with a single User

Interface (UI) thread and the thread is called Main

thread. Main thread cannot handle concurrent

operations as it handles only one event/operation at a

time.

•

Concurrent Processing in Android

–

If input events or tasks are not handled concurrently,

whole code of an Android application runs in the main

thread and each line of code is executed one after

each other.

Assume if you perform a long lasting operation, for example

accessing resource (like MP3, JSON, Image) from the

Internet, the application goes hung state until the

corresponding operation is finished.

To bring good user experience in Android applications, all

potentially slow running operations or tasks in an Android

application should be made to run asynchronously.

Here are some examples for slow running tasks

–

Accessing resources (like MP3, JSON, Image) from Internet

–

Database operations

–

Webservice calls

–

Complex logic that takes quite long time

What is AsyncTask?

•

AsyncTask is an abstract Android class which helps the

Android applications to handle the Main UI thread in

efficient way. AsyncTask class allows us to perform long

lasting tasks/background operations and show the result on

the UI thread without affecting the main thread.

•

Android application runs on a single thread when launched.

Due to this single thread model tasks that take longer time

to fetch the response can make the application non-

responsive. To avoid this we use android AsyncTask to

perform the heavy tasks in background on a dedicated

thread and passing the results back to the UI thread. Hence

use of AsyncTask in android application keeps the UI thread

responsive at all times.

Need of AsyncTask In Android

•

By default, our application code runs in our main thread and every

statement is therefore execute in a sequence.

•

If we need to perform long tasks/operations then our main thread

is blocked until the corresponding operation has finished.

•

For providing a good user experience in our application we need to

use AsyncTasks class that runs in a separate thread.

•

This class will executes everything in doInBackground() method

inside of other thread which doesn’t have access to the GUI where

all the views are present.

•

The onPostExecute() method of this class synchronizes itself again

with the main UI thread and allows it to make some updating.

•

This method is called automatically after the doInBackground

method finished its work.

AsyncTask’s three parameters

•

android.os.AsyncTask<Params, Progress, Result>

Where,

1. Params — the type of the parameters sent to the

task upon execution

–

the type of parameters passed into execute()

2.Progress — the type of the progress units published

during the background computation

3.Result — the type of the result of the background

computation

–

must be the return type of doInBackground

Syntax of AsyncTask In Android

•

Create a new class inside Activity class and subclass it by extending AsyncTask

private class Demo extends AsyncTask<URL, Integer, Long>

 {

 protected Long doInBackground(URL... urls)

 {

     //Yet to code

}

 protected void onProgressUpdate(Integer... progress)

 {

     //Yet to code

     }

 protected void onPostExecute(Long result)

 {

   //Yet to code

  }

}

•

Execute the task simply by invoking execute

method

new Demo().execute(url1, url2, url3);

Methods of AsyncTask

•

execute(Params… params)

 : This method is invoked in java code to start the

asynchronous task.

•

void onPreExecute()

 :  Used to do some UI operation before performing

background tasks.

•

String doInBackground(Integer… inputParams)

 : Run immediately

after 

onPreExecute()

 is completed, it is used to perform more time-consuming

operations. This method accepts the input parameters and returns the calculated

results. During the execution, you can call 

publishProgress(Progress… Values)

 to

update the progress information.

•

void onProgressUpdate(Progress… values) : 

This method will be invoked when

execute 

publishProgress(Progress… Values)

 method in java code. Generally, we

update UI component’s status such as text, progress percentage in this method.

•

void onPostExecute(String result)

 :  When background task complete, this method

will be invoked automatically. Parameter result’s value is just

which 

doInBackground(Params… params)

 method returned.

•

void onCancelled(String result)

 : This method will be invoked when 

AsyncTask’s

cancel(boolean cancel) 

method is invoked.

AsyncTask – Rules to be followed

•

The AsyncTask class must be loaded on the UI thread.

•

The task instance must be created on the UI thread.

•

Method execute(Params…) must be invoked on the UI

thread.

•

Should not call onPreExecute(), onPostExecute(Result),

doInBackground(Params…),

onProgressUpdate(Progress…) manually.

•

The task can be executed only once (an exception will

be thrown if a second execution is attempted.)

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest

xmlns:android="http://schemas.android.com/apk/res/android"

package="com.legendblogs.asynctask"> <application android:allowBackup="true"

android:icon="@mipmap/ic_launcher" android:label="@string/app_name"

android:supportsRtl="true" android:theme="@style/AppTheme"> <activity

android:name=".MainActivity"> <intent-filter> <action

android:name="android.intent.action.MAIN" /> <category

android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

</application> </manifest><?xml version="1.0" encoding="utf-8"?> <manifest

xmlns:android="http://schemas.android.com/apk/res/android"

package="com.legendblogs.asynctask"> <application android:allowBackup="true"

android:icon="@mipmap/ic_launcher" android:label="@string/app_name"

android:supportsRtl="true" android:theme="@style/AppTheme"> <activity

android:name=".MainActivity"> <intent-filter> <action

android:name="android.intent.action.MAIN" /> <category

android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

</application> </manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"

android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.legendblogs.asynctask.MainActivity">

 <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:text="Welcome to Legend Blogs Exmpale" android:layout_alignParentTop="true"

android:layout_centerHorizontal="true" android:textStyle="bold" android:textSize="20dp"

android:id="@+id/textView2" />

 <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"

android:textAppearance="?android:attr/textAppearanceLarge" android:text="Please enter a waiting

Time" android:id="@+id/textView" android:layout_below="@+id/textView2"

android:layout_centerHorizontal="true" android:layout_marginTop="64dp" />

<EditText android:layout_width="wrap_content" android:layout_height="wrap_content"

android:id="@+id/editText" android:layout_below="@+id/textView" android:layout_marginTop="56dp"

android:layout_alignEnd="@+id/textView" android:layout_alignStart="@+id/textView" />

<Button android:layout_width="wrap_content" android:layout_height="wrap_content"

android:text="Run AsyncTask" android:id="@+id/button" android:layout_below="@+id/editText"

android:layout_centerHorizontal="true" android:layout_marginTop="62dp" /> </RelativeLayout>

MainActivity.java

package com.legendblogs.asynctask;

 import android.content.Context; import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

 import android.view.View;

 import android.widget.Button;

 import android.widget.EditText;

 public class MainActivity extends AppCompatActivity {

Context context;

 EditText editText;

Button button;

@Override

protected void onCreate(Bundle savedInstanceState)

 {

super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);

this.context = this;

 editText = (EditText) findViewById(R.id.editText);

 button = (Button) findViewById(R.id.button); button.setOnClickListener(new View.OnClickListener() {

@Override

 public void onClick(View v) {

if(editText != null && editText.length() > 0)

 new MyAsyncTask(context).execute(editText.getText().toString());

 } }); } }

MyAsyncTask.java

package com.legendblogs.asynctask; import android.app.ProgressDialog;

import android.content.Context; import android.os.AsyncTask; import

android.util.Log;

public class MyAsyncTask extends AsyncTask<String, String, String>

 {

Context context;

String result;

ProgressDialog progressDialog;

 public MyAsyncTask (Context context)

 {

this.context = context;

 }

@Override

 protected void onPreExecute()

 {

super.onPreExecute();

 progressDialog = ProgressDialog.show(context, "Progress Dialog", null);

}

@Override

protected String doInBackground(String... args)

 {

 int value = Integer.parseInt(args[0]);

for(int i = 0; i <= value ;i++)

{ try

 {

Thread.sleep(1000);

 } catch (Exception e)

{

Log.v("Error: ", e.toString());

 }

result = "Please wait for " + (value - i ) + " seconds"; publishProgress(result);

}

return null;

}

@Override

 protected void onProgressUpdate(String... text)

 {

progressDialog.setMessage(text[0]);

}

 protected void onPostExecute(String result)

 {

 progressDialog.dismiss();

 } }

Shared Preferences

•

Shared Preferences

 are used to save and retrieve the primitive data

types (integer, float, Boolean, string, long) data in the form of key-

value pair from a file within an apps file structure.

•

Generally, the 

Shared Preferences

 object will points to a file that

contains a key-value pairs and provides a simple read and write

methods to save and retrieve the key-value pairs from a file.

•

The Shared Preferences file is managed by an android framework and

it can be accessed anywhere within the app to read or write data into

the file, but it’s not possible to access the file from any other app so

it’s secured.

•

The Shared Preferences are useful to store the small collection of

key-values such as user’s login information, app preferences related

to users, etc. to maintain the state of app, next time when they login

again to the app.

Handle a Shared Preferences

•

we can save the preferences data either in single or

multiple files based on our requirements.

•

In case if we use single file to save the preferences, then

we need to use 

getPreferences()

 method to get the

values from Shared Preferences file and for multiple files

we need to call a 

getSharedPreferences()

 method and

pass a file name as a parameter.

getSharedPreferences (String PREFS_NAME, int mode)

•

Where

–

PREFS_NAME

 is the name of the file.

–

mode

 is the operating mode.

•

Following are the operating modes applicable:

–

MODE_PRIVATE

: the default mode, where the created file can

only be accessed by the calling application

–

MODE_WORLD_READABLE

: Creating world-readable files is

very dangerous, and likely to cause security holes in applications

–

MODE_WORLD_WRITEABLE

: Creating world-writable files is

very dangerous, and likely to cause security holes in applications

–

MODE_MULTI_PROCESS

: This method will check for

modification of preferences even if the Shared Preference

instance has already been loaded

–

MODE_APPEND

: This will append the new preferences with the

already existing preferences

–

MODE_ENABLE_WRITE_AHEAD_LOGGING

: Database open flag.

When it is set, it would enable write ahead logging by default

Initialization

•

We need an editor to edit and save the changes

in shared preferences. The following code can be

used to get the shared preferences.

SharedPreferences pref = getApplicationContext().getSharedPreferences("MyPref", 0);

// 0 - for private mode Editor

      editor = pref.edit();

Storing Data

•

editor.commit()

 is used in order to save changes to

shared preferences.

editor.putBoolean("key_name", true); // Storing boolean

true/false

editor.putString("key_name", "string value"); // Storing string

editor.putInt("key_name", "int value"); // Storing integer

editor.putFloat("key_name", "float value"); // Storing float

editor.putLong("key_name", "long value"); // Storing long

editor.commit(); // commit changes

Retrieving Data

•

Data can be retrieved from saved preferences by

calling 

getString()

 as follows:

pref.getString("key_name", null); // getting String

pref.getInt("key_name", -1); // getting Integer

pref.getFloat("key_name", null); // getting Float

pref.getLong("key_name", null); // getting Long

pref.getBoolean("key_name", null); // getting boolean

Clearing or Deleting Data

•

remove(“key_name”)

 is used to delete that

particular value.

editor.remove("name"); // will delete key name

editor.remove("email"); // will delete key email

editor.commit(); // commit changes

•

clear()

 is used to remove all data

editor.clear();

editor.commit(); // commit changes

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:id="@+id/fstTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:layout_marginTop="150dp"

        android:text="UserName" />

    <EditText

        android:id="@+id/txtName"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10"/>

    <TextView

        android:id="@+id/secTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Password"

        android:layout_marginLeft="100dp" />

    <EditText

        android:id="@+id/txtPwd"

        android:inputType="textPassword"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10" />

    <Button

        android:id="@+id/btnLogin"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:text="Login" />

</LinearLayout>

details.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/andr

oid"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:id="@+id/resultView"

        android:layout_gravity="center"

        android:layout_marginTop="170dp"

        android:textSize="20dp"/>

    <Button

        android:id="@+id/btnLogOut"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_gravity="center"

        android:layout_marginTop="20dp"

        android:text="Log Out" />

</LinearLayout>

MainActivity.java

package com.tutlane.sharedpreferencesexample;

import android.content.Intent;

import android.content.SharedPreferences;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    EditText uname, pwd;

    Button loginBtn;

    SharedPreferences pref;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        uname = (EditText)findViewById(R.id.txtName);

        pwd = (EditText)findViewById(R.id.txtPwd);

        loginBtn = (Button)findViewById(R.id.btnLogin);

        pref = getSharedPreferences("user_details",MODE_PRIVATE);

        intent = new Intent(MainActivity.this,DetailsActivity.class);

        if(pref.contains("username") && pref.contains("password")){

            startActivity(intent);

        }

 loginBtn.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                String username = uname.getText().toString();

                String password = pwd.getText().toString();

                if(username.equals("suresh") && password.equals("dasari")){

                    SharedPreferences.Editor editor = pref.edit();

                    editor.putString("username",username);

                    editor.putString("password",password);

                    editor.commit();

                    Toast.makeText(getApplicationContext(), "Login

Successful",Toast.LENGTH_SHORT).show();

                    startActivity(intent);

                }

                else

                {

                    Toast.makeText(getApplicationContext(),"Credentials are not

valid",Toast.LENGTH_SHORT).show();

                }

            }

        });

    }

}

DetailsActivity.java

package com.tutlane.sharedpreferencesexample;

import android.content.Intent;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

public class DetailsActivity extends AppCompatActivity {

    SharedPreferences prf;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.details);

  TextView result = (TextView)findViewById(R.id.resultView);

        Button btnLogOut = (Button)findViewById(R.id.btnLogOut);

 prf = getSharedPreferences("user_details",MODE_PRIVATE);

        intent = new Intent(DetailsActivity.this,MainActivity.class);

        result.setText("Hello, "+prf.getString("username",null));

        btnLogOut.setOnClickListener(new View.OnClickListener() {

            @Override

 public void onClick(View v) {

                SharedPreferences.Editor editor = prf.edit();

                editor.clear();

                editor.commit();

                startActivity(intent);

            }

        });

    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.tutlane.sharedpreferencesexample">

    <application

        android:allowBackup="true"

        android:icon="@mipmap/ic_launcher"

        android:label="@string/app_name"

        android:roundIcon="@mipmap/ic_launcher_round"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity android:name=".DetailsActivity" android:label="Shared Prefe

rences - Details"></activity>

    </application>

</manifest>

Internal Storage

•

In android, 

Internal Storage

 is useful to store the data files

locally on the device’s internal memory

using 

FileOutputStream

 object. After storing the data files

in device internal storage, we can read the data file from

device using 

FileInputStream

 object.

•

The data files saved in internal storage is managed by an

android framework and it can be accessed anywhere within

the app to read or write data into the file, but it’s not

possible to access the file from any other app so it’s

secured. When the user uninstall the app, automatically

these data files will be removed from the device internal

storage.

Write a File to Internal Storage

•

By using android 

FileOutputStream

 object 

openFileOutput

 method,

we can easily create and write a data to a file in device’s internal

storage.

String FILENAME = "user_details";

String name = "suresh";

FileOutputStream fstream = openFileOutput(FILENAME,

Context.MODE_PRIVATE);

fstream.write(name.getBytes());

fstream.close();

•

we are creating and writing a file in device internal storage by

using 

FileOutputStream

 object 

openFileOutput

 method with 

file

name

 and 

MODE_PRIVATE

 mode to make the file private to our

application. We used 

write()

 method to write the data in file and

used 

close()

 method to close the stream.

•

In android, we have a different modes such

as 

MODE_APPEND

, 

MODE_WORLD_READBLE

, 

MODE_WORLD_WRIT

EABLE

, etc. to use it in our application based on your requirements.

Read a File from Internal Storage

•

By using android 

FileInputStream

 object 

openFileInput

 method, we

can easily read the file from device’s internal storage.

String FILENAME = "user_details";

FileInputStream fstream = openFileInput(FILENAME);

StringBuffer sbuffer = new StringBuffer();

int i;

while ((i = fstream.read())!= -1){

    sbuffer.append((char)i);

}

fstream.close();

If you observe above code, we are reading a file from device internal

storage by using FileInputStream object openFileInput method with

file name. We used read() method to read one character at a time

from the file and used close() method to close the stream.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:id="@+id/fstTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:layout_marginTop="150dp"

        android:text="UserName" />

    <EditText

        android:id="@+id/txtName"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10"/>

    <TextView

        android:id="@+id/secTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Password"

        android:layout_marginLeft="100dp" />

    <EditText

        android:id="@+id/txtPwd"

        android:inputType="textPassword"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10" />

    <Button

        android:id="@+id/btnSave"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:text="Save" /> </LinearLayout>

details.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/andr

oid"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:id="@+id/resultView"

        android:layout_gravity="center"

        android:layout_marginTop="170dp"

        android:textSize="20dp"/>

    <Button

        android:id="@+id/btnBack"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_gravity="center"

        android:layout_marginTop="20dp"

        android:text="Back" />

</LinearLayout>

•

MainActivity.java

•

package com.tutlane.internalstorageexample;

import android.content.Context;

import android.content.Intent;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    EditText uname, pwd;

    Button saveBtn;

    FileOutputStream fstream;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

•

  uname = (EditText)findViewById(R.id.txtName);

        pwd = (EditText)findViewById(R.id.txtPwd);

        saveBtn = (Button)findViewById(R.id.btnSave);

        saveBtn.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                String username = uname.getText().toString()+"\n";

                String password = pwd.getText().toString();

                try {

                    fstream = openFileOutput("user_details",

Context.MODE_PRIVATE);

                    fstream.write(username.getBytes());

                    fstream.write(password.getBytes());

                    fstream.close();

                    Toast.makeText(getApplicationContext(), "Details Saved

Successfully",Toast.LENGTH_SHORT).show();

                    intent = new Intent(MainActivity.this,DetailsActivity.class);

                    startActivity(intent);

                } catch (FileNotFoundException e) {

                    e.printStackTrace();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        });

    }

}

•

DetailsActivity.java

•

package com.tutlane.internalstorageexample;

import android.content.Intent;

import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

public class DetailsActivity extends AppCompatActivity {

    FileInputStream fstream;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.details);

        TextView result = (TextView)findViewById(R.id.resultView);

        Button back = (Button)findViewById(R.id.btnBack);

        try {

            fstream = openFileInput("user_details");

            StringBuffer sbuffer = new StringBuffer();

            int i;

            while ((i = fstream.read())!= -1){

                sbuffer.append((char)i);

            }

•

 fstream.close();

            String details[] = sbuffer.toString().split("\n");

            result.setText("Name: "+ details[0]+"\nPassword:

"+details[1]);

        } catch (FileNotFoundException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

        back.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                intent = new Intent(DetailsActivity.this,MainActivity.class);

                startActivity(intent);

            }

        });

    }

}

•

AndroidManifest.xml

•

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.tutlane.internalstorageexample">

    <application

        android:allowBackup="true"

        android:icon="@mipmap/ic_launcher"

        android:label="@string/app_name"

        android:roundIcon="@mipmap/ic_launcher_round"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity android:name=".DetailsActivity" android:label="Internal Stor

age - Details"></activity>

    </application>

</manifest>

External Storage

•

External Storage

 option to store and retrieve the data from

external storage media such as SD card.

•

In android, 

External Storage

 is useful to store the data files

publically on the shared external storage

using 

FileOutputStream

 object. After storing the data files

on external storage, we can read the data file from external

storage media using 

FileInputStream

 object.

•

The data files saved in external storage are word-readable

and can be modified by the user when they enable USB

mass storage to transfer files on a computer.

Grant Access to External Storage

•

To read or write files on the external storage, our app must acquire

the 

WRITE_EXTERNAL_STORAGE

 and 

READ_EXTERNAL_STORAGE

 s

ystem permissions. For that, we need to add following permissions

in android manifest file like as shown below.

<manifest>

    ....

    <uses-permission android:name="android.permission.WRITE_EXT

ERNAL_STORAGE"/>

    <uses-permission android:name="android.permission.READ_EXT

ERNAL_STORAGE"/>

    ....

</manifest>

Checking External Storage Availability

•

Before we do any work with external storage, first we need to check whether

the media is available or not by calling 

getExternalStorageState()

. The media

might be mounted to a computer, missing, read-only or in some other state.

To get the media status, we need to write the code like as shown below.

boolean Available= false;

boolean Readable= false;

String state = Environment.getExternalStorageState();

if(Environment.MEDIA_MOUNTED.equals(state)){

    // Both Read and write operations available

    Available= true;

} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)){

    // Only Read operation available

    Available= true;

    Readable= true;

} else {

    // SD card not mounted

    Available = false;

}

If you observe above code snippet, we used 

getExternalStorageState()

 method t

o know the status of media mounted to a computer, such as missing, read-o

nly or in some other state.

•

In android, by using 

getExternalStoragePublishDirectory()

 method

we can access the files from appropriate public directory by passing

the type of directory we want, such as DIRECTORY_MUSIC,

DIRECTORY_PICTURES, DIRECTORY_RINGTONES, etc. based on our

requirements.

•

If we save our files to corresponding media-type public directory,

the system's media scanner can properly categorize our files in the

system.

•

following is the example to create a directory for new photo album

in the public pictures directory.

// Get the directory for the user's public pictures directory.

File file = new File(Environment.getExternalStoragePublicDirectory(

        Environment.DIRECTORY_PICTURES), albumName);

if (!file.mkdirs()) {

    Log.e(LOG_TAG, "Directory not created");

}

•

In case, if we are handling the files that are not intended for other

apps to use, then we should use a private storage directory on the

external storage by calling 

getExternalFilesDir()

.

Write a File to External Storage

•

By using android 

FileOutputStream

 object

and 

getExternalStoragePublicDirectory

 method, we can easily create

and write a data to the file in external storage public folders.

String FILENAME = "user_details";

String name = "suresh";

File folder = Environment.getExternalStoragePublicDirectory(Environ

ment.DIRECTORY_DOWNLOADS);

File myFile = new File(folder, FILENAME);

FileOutputStream fstream = new FileOutputStream(myFile);fstream.

write(name.getBytes());

fstream.close();

If you observe above code, we are creating and writing a file in

device public 

Downloads

 folder by

using 

getExternalStoragePublicDirectory

 method. We

used 

write()

 method to write the data in file and

used 

close()

 method to close the stream.

Read a File from External Storage

•

By using android 

FileInputStream

 object

and 

getExternalStoragePublicDirectory

 method, we can easily read the file from

external storage.

String FILENAME = "user_details";

File folder =

Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWN

LOADS);

File myFile = new File(folder, FILENAME);

FileInputStream fstream = new FileInputStream(myFile);

StringBuffer sbuffer = new StringBuffer();

int i;

while ((i = fstream.read())!= -1){

    sbuffer.append((char)i);

}

fstream.close();

If you observe above code, we are reading a file from device Downloads folder

storage by

using 

FileInputStream

 object 

getExternalStoragePublicDirectory

 method with 

file

name

. We used 

read()

 method to read one character at a time from the file and

used 

close()

 method to close the stream.

•

activity_main.xml

•

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:id="@+id/fstTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:layout_marginTop="150dp"

        android:text="UserName" />

    <EditText

        android:id="@+id/txtName"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10"/>

    <TextView

        android:id="@+id/secTxt"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Password"

        android:layout_marginLeft="100dp" />

    <EditText

        android:id="@+id/txtPwd"

        android:inputType="textPassword"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:ems="10" />

    <Button

        android:id="@+id/btnSave"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginLeft="100dp"

        android:text="Save" /></LinearLayout>

•

details.xml

•

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/andr

oid"

    android:orientation="vertical" android:layout_width="match_parent"

    android:layout_height="match_parent">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:id="@+id/resultView"

        android:layout_gravity="center"

        android:layout_marginTop="170dp"

        android:textSize="20dp"/>

    <Button

        android:id="@+id/btnBack"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_gravity="center"

        android:layout_marginTop="20dp"

        android:text="Back" />

</LinearLayout>

•

MainActivity.java

•

package com.tutlane.externalstorageexample;

import android.content.Intent;

import android.os.Environment;

import android.support.v4.app.ActivityCompat;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    EditText uname, pwd;

    Button saveBtn;

    FileOutputStream fstream;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        uname = (EditText)findViewById(R.id.txtName);

        pwd = (EditText)findViewById(R.id.txtPwd);

        saveBtn = (Button)findViewById(R.id.btnSave);

        saveBtn.setOnClickListener(new View.OnClickListener() {

            @Override

•

public void onClick(View v) {

                String username = uname.getText().toString()+"\n";

                String password = pwd.getText().toString();

                try {

                    ActivityCompat.requestPermissions(MainActivity.this, new Stri

ng[]{android.Manifest.permission.READ_EXTERNAL_STORAGE},23);

                    File folder =

Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_

DOWNLOADS);

                    File myFile = new File(folder,"user_details");

                    fstream = new FileOutputStream(myFile);

                    fstream.write(username.getBytes());

                    fstream.write(password.getBytes());

                    fstream.close();

                    Toast.makeText(getApplicationContext(), "Details Saved in

"+myFile.getAbsolutePath(),Toast.LENGTH_SHORT).show();

                    intent = new Intent(MainActivity.this,DetailsActivity.class);

                    startActivity(intent);

                } catch (FileNotFoundException e) {

                    e.printStackTrace();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        });

    }

}

•

DetailsActivity.java

•

package com.tutlane.externalstorageexample;

import android.content.Intent;

import android.os.Bundle;

import android.os.Environment;

import android.support.v7.app.AppCompatActivity;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

public class DetailsActivity extends AppCompatActivity {

    FileInputStream fstream;

    Intent intent;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.details);

        TextView result = (TextView)findViewById(R.id.resultView);

        Button back = (Button)findViewById(R.id.btnBack);

        try {

            File folder = Environment.getExternalStoragePublicDirectory(Environm

ent.DIRECTORY_DOWNLOADS);

•

File myFile = new File(folder,"user_details");

            fstream = new FileInputStream(myFile);

            StringBuffer sbuffer = new StringBuffer();

            int i;

            while ((i = fstream.read())!= -1){

                sbuffer.append((char)i);

            }

            fstream.close();

            String details[] = sbuffer.toString().split("\n");

            result.setText("Name: "+ details[0]+"\nPassword: "+details[1]);

        } catch (FileNotFoundException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

        back.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                intent = new Intent(DetailsActivity.this,MainActivity.class);

                startActivity(intent);

            }

        });

    }

}

•

AndroidManifest.xml

•

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.tutlane.externalstorageexample">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORA

GE"/>

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAG

E"/>

    <application

        android:allowBackup="true"

        android:icon="@mipmap/ic_launcher"

        android:label="@string/app_name"

        android:roundIcon="@mipmap/ic_launcher_round"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity android:name=".DetailsActivity" android:label="External Storage - De

tails"></activity>

    </application>

</manifest>

Android SQLite Database

•

SQLite

 is an open source light weight relational database

management system (RDBMS) to perform database operations,

such as storing, updating, retrieving data from database.

•

Generally, in our android applications 

Shared Preferences

, 

Internal

Storage

 and 

External Storage

 options are useful to store and

maintain the small amount of data. In case, if we want to deal with

large amount of data, then 

SQLite database

 is the preferable option

to store and maintain the data in structured format.

•

By default, Android comes with built-in 

SQLite Database

 support so

we don’t need to do any configurations.

•

Just like we save the files on device’s 

internal storage

, Android

stores our database in a private disk space that’s associated to our

application and the data is secure, because by default this area is

not accessible to other applications.

•

The package 

android.database.sqlite

 contains all the required API’s

to use SQLite database in our android applications.

•

Android SQLite native API is not JDBC, as JDBC

might be too much overhead for a memory-

limited smartphone. Once a database is

created successfully its located

in 

data/data//databases/

 accessible from

Android Device Monitor.

•

SQLite is a typical 

relational database

,

containing tables (which consists of rows and

columns), indexes etc. We can create our own

tables to hold the data accordingly. This

structure is referred to as a 

schema

.

SQLiteOpenHelper

•

class provides the functionality to use the SQLite

database.

•

The android.database.sqlite.SQLiteOpenHelper

class is used for database creation and version

management. For performing any database

operation, you have to provide the

implementation

of 

onCreate()

 and 

onUpgrade()

 methods of

SQLiteOpenHelper class.

Database - Package

•

The main package is android.database.sqlite

that contains the classes to manage your own

databases

Database - Insertion

•

we can create table or insert data into table using execSQL method defined

in SQLiteDatabase class. Its syntax is given below

•

mydatabase.execSQL("CREATE TABLE IF NOT EXISTS TutorialsPoint(Username

VARCHAR,Password VARCHAR);"); mydatabase.execSQL("INSERT INTO

Student VALUES('admin','admin');");

Database - Fetching

•

We can retrieve anything from database using an

object of the Cursor class. We will call a method

of this class called rawQuery and it will return a

resultset with the cursor pointing to the table.

We can move the cursor forward and retrieve the

data.

•

Cursor resultSet = mydatbase.rawQuery("Select *

from student",null); resultSet.moveToFirst();

String username = resultSet.getString(0); String

password = resultSet.getString(1);

functions available in the Cursor class

Methods of SQLiteDatabase class

Constructors of SQLiteOpenHelper class

Methods of SQLiteOpenHelper class