Introduction to Java GUI Programming

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Java GUI programming involves transitioning from AWT to Swing, utilizing prebuilt components, and understanding the anatomy of a GUI application. Learn how to create, configure, and interact with GUI components such as buttons and labels, and build applications from the bottom up. Explore sample code snippets to kickstart your GUI development journey.

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Java GUI

AWT to Swing AWT: Abstract Windowing Toolkit import java.awt.* Swing: new with Java2 import javax.swing.* Extends AWT Tons o new improved components Standard dialog boxes, tooltips, Look-and-feel, skins Event listeners API: http://java.sun.com/j2se/1.3/docs/api/index.html

Swing Set Demo J2sdk/demo/jfc/SwingSet2 Many predefined GUI components

GUI Component API Java: GUI component = class Properties Methods Events JButton

Using a GUI Component 1. Create it 2. Configure it 3. Add it 4. Listen to it Instantiate object: b = new JButton( press me ); Properties: b.text = press me ; [avoided in java] Methods: b.setText( press me ); panel.add(b); JButton Events: Listeners

Anatomy of an Application GUI GUI Internal structure JFrame JFrame JPanel containers JPanel JButton JButton JLabel JLabel

Using a GUI Component 2 1. Create it 2. Configure it 3. Add children (if container) 4. Add to parent (if not JFrame) 5. Listen to it order important

Build from bottom up Create: Listener Frame Panel Components Listeners JButton JLabel Add: (bottom up) listeners into components components into panel panel into frame JPanel JFrame

Code JFrame f = new JFrame( title ); JPanel p = new JPanel( ); JButton b = new JButton( press me ); p.add(b); f.setContentPane(p); // add panel to frame // add button to panel f.show(); press me

Application Code import javax.swing.*; class hello { public static void main(String[] args){ JFrame f = new JFrame( title ); JPanel p = new JPanel(); JButton b = new JButton( press me ); p.add(b); f.setContentPane(p); // add panel to frame // add button to panel } } f.setVisible(true); press me

Layout Manager Heuristics FlowLayout GridLayout null none, Left to right, Top to bottom programmer sets x,y,w,h GridBagLayout BorderLayout CardLayout n w e JButton c One at a time s

Combinations JButton JButton JTextArea

Combinations JButton JButton JFrame n JPanel: FlowLayout JPanel: BorderLayout c JTextArea

Code: null layout JFrame f = new JFrame( title ); JPanel p = new JPanel( ); JButton b = new JButton( press me ); b.setBounds(new Rectangle(10,10, 100,50)); p.setLayout(null); p.add(b); f.setContentPane(p); // x,y layout press me

Code: FlowLayout JFrame f = new JFrame( title ); JPanel p = new JPanel( ); FlowLayout L = new FlowLayout( ); JButton b1 = new JButton( press me ); JButton b2 = new JButton( then me ); p.setLayout(L); p.add(b1); p.add(b2); f.setContentPane(p); press me then me Set layout mgr before adding components

Applets JApplet JApplet is like a JFrame Already has a panel Access panel with JApplet.getContentPane( ) contentPane import javax.swing.*; JButton class hello extends JApplet { public void init(){ JButton b = new JButton( press me ); getContentPane().add(b); } }

Applet Methods Called by browser: init( ) start( ) - resume processing (e.g. animations) stop( ) - pause destroy( ) - cleanup paint( ) - redraw stuff ( expose event) - initialization

Application + Applet import javax.swing.*; Command line Browser class helloApp { public static void main(String[] args){ // create Frame and put my mainPanel in it JFrame f = new JFrame( title ); mainPanel p = new mainPanel(); f.setContentPane(p); f.show(); } } JFrame JApplet or class helloApplet extends JApplet { public void init(){ // put my mainPanel in the Applet mainPanel p = new mainPanel(); getContentPane().add(p); } } contentPane // my main GUI is in here: class mainPanel extends JPanel { mainPanel(){ setLayout(new FlowLayout()); JButton b = new JButton( press me ); add(b); } } JPanel JButton