Button Action Handler at the Frame Level

Java Swing Tutorials - Herong's Tutorial Examples

∟Button Action Handler at the Frame Level

This section provides a tutorial example on how to create a button to handle actions by adding the ActionListener interface to the frame that contains the button component.

In the previous section, we extended the button to handle its own action. That works fine, if the action only requires modifying the behavior of the same button.

But if the action requires modifying the behavior of other components, you need to implement the action listener as a higher level. The following program shows you how to use the action handler to modify the text of a label component:

/* JButtonAction2.java
 * Copyright (c) 1997-2024 HerongYang.com. All Rights Reserved.
 */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class JButtonAction2 implements ActionListener {
   JButton myButton = null;
   JLabel myLabel = null;
   String text = null;
   public static void main(String[] a) {
      JButtonAction2 myTest = new JButtonAction2();
      myTest.createFrame();
   }
   public void createFrame() {
      JFrame f = new JFrame("My Switch Button");
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      Container c = f.getContentPane();
      c.setLayout(new GridLayout(2,1));
      text = "On";
      myButton = new JButton(text);
      myButton.addActionListener(this);
      c.add(myButton);
      myLabel = new JLabel(text,SwingConstants.CENTER);
      c.add(myLabel);
      f.pack();
      f.setVisible(true);
   }
   public void actionPerformed(ActionEvent e) {
      if (text.equals("On")) text = "Off";
      else text = "On"; 
      myButton.setText(text);
      myLabel.setText(text);
   }
}

If you run this example, you will get:

The button works nicely. If you click the button, the button label text will change from "On" to "Off", and the text of the label component will also change.