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Java Swing

AWT to Swing

• AWT: Abstract Windowing Toolkit

• import java.awt.*

• Swing: new with Java

• import javax.swing.*
• Extends AWT
• Tons o‟ new improved components
• Standard dialog boxes, tooltips, …
• Look-and-feel, skins
• Event listeners

GUI Component API

• Java: GUI component = class

• Properties

• Methods

• Events

JButton

Using a GUI Component

1. Create it

• Instantiate object: b = new JButton(“press me”);

2. Configure it

• Properties: b.text = “press me”; [avoided in java]
• Methods: b.setText(“press me”);

3. Add it

• panel.add(b);

4. Listen to it

• Events: Listeners

JButton

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:

• Frame
• Panel
• Components
• Listeners

• Add: (bottom up)

• listeners into components
• components into panel
• panel into frame

JPanel

JButton

Listener

JFrame

JLabel

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); // add button to panel f.setContentPane(p); // add panel to frame

f.show(); } }

press me

Layout Managers

• Automatically control placement of components

in a panel

• Why?

Combinations

JButton JButton

JTextArea

Combinations

n

JPanel: BorderLayout

c

JFrame

JPanel: FlowLayout

JButton JButton

JTextArea

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);

Set layout mgr before adding components

press me then me

Applets

• JApplet is like a JFrame
• Already has a panel
  • Access panel with JApplet.getContentPane( )

import javax.swing.;*

class hello extends JApplet {

public void init(){ JButton b = new JButton(“press me”); getContentPane().add(b); }

}

JApplet

contentPane

JButton

Application + Applet

import javax.swing.; 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(); } } class helloApplet extends JApplet { public void init(){ // put my mainPanel in the Applet mainPanel p = new mainPanel(); getContentPane().add(p); } } // my main GUI is in here: class mainPanel extends JPanel { mainPanel(){ setLayout(new FlowLayout()); JButton b = new JButton(“press me”); add(b); } }*

JApplet

contentPane

JPanel

JFrame

JButton

or

Command line Browser

Applet Security

• No read/write on client machine

• Can‟t execute programs on client machine

• Communicate only with server

• “Java applet window” Warning