1. JButton
Chapter 11 Lecture 3

2. Jbutton
A button is a component the user clicks to trigger a specific action.
Types of buttons include:
Command buttons
Checkboxes
Toggle buttons
Radio buttons

3. Swing button hierarchy
JComponent
AbstractButton
JButton
JToggleButton
All the button types are subclassese of AbstractButton (javax.swing) --- declares the common features of Swing buttons
JCheckBox
JRadioButton

4. JButton
A command button generates an ActionEvent when the user clicks the button.
Command buttons are created with class Jbutton.
The text on the face of a Jbuttonis called a button label.
A GUI can have many JButtons
Button label should be UNIQUE in the currently displayed GUI

5. Constructor Summary
JButton()   Creates a button with no set text or icon.
JButton(Action a)  Creates a button where properties are taken from the Action supplied.
JButton(Icon icon)   Creates a button with an icon.
JButton(String text)    Creates a button with text.
JButton(String text, Icon icon)            Creates a button with initial text and an icon.

6. Example – ButtonFrame.java
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;

7. Button variables declaration
private JButton plainJButton; // button with just text private JButton fancyJButton; // button with icons

8. Creates buttons
plainJButton = new JButton( "Plain Button" ); // button with text add( plainJButton ); // add plainJButton to Jframe fancyJButton = new JButton( "Fancy Button", bug1 ); // set image fancyJButton.setRolloverIcon( bug2 ); // set rollover image add( fancyJButton ); // add fancyJButton to JFrame
Rollover : The icon is displayed when the user positions the mouse over the button
setRolloverIcon is inherited from the AbstractButton

9. Example - continued
Create an object of private inner class ButtonHandler and register it as event handler for each button:
ButtonHandler handler = new ButtonHandler();
fancyJButton.addActionListener( handler );
plainJButton.addActionListener( handler );

10. Class ButtonHandler
// inner class for button event handling private class ButtonHandler implements ActionListener { // handle button event public void actionPerformed( ActionEvent event ) JOptionPane.showMessageDialog( ButtonFrame.this, String.format( "You pressed: %s", event.getActionCommand() ) ); } // end method actionPerformed } // end private inner class ButtonHandler