Sample program to demonstrate the use of ActionListener

By: Ramlak Viewed: 153500 times  Printer Friendly Format    


This Java samples program demonstrates the use of ActionListener event handler. Action listeners are probably the easiest - and most common - event handlers to implement. You implement an action listener to define what should be done when an user performs certain operation.

This is a simple program which displays how many number of times a button is clicked by the user. First, here is the code that sets up the TextField , button and numClicks variable:

public class AL extends Frame implements WindowListener,ActionListener {
TextField text = new TextField(20);
Button b;
private int numClicks = 0;

In the above example, the event handler class is AL which implements ActionListener.

We would like to handle the button-click event, so we add an action listener to the button b as below:

b = new Button("Click me");
b.addActionListener(this); 

In the above code, Button b is a component upon which an instance of event handler class AL is registered.

Now, we want to display the text as to how many number of times a user clicked button. We can do this by writing the code as below:

public void actionPerformed(ActionEvent e) {
	 numClicks++;
	 text.setText("Button Clicked " + numClicks + " times");
Now, when the user clicks the Button b, the button fires an action event which invokes the action listener's actionPerformed method. Each time the user presses the button, numClicks variable is appended and the message is displayed in the text field.
The complete source code for the even handler is given below:
import java.awt.*;
import java.awt.event.*;

public class AL extends Frame implements WindowListener,ActionListener {
	TextField text = new TextField(20);
	Button b;
	private int numClicks = 0;

	public static void main(String[] args) {
		AL myWindow = new AL("My first window");
		myWindow.setSize(350,100);
		myWindow.setVisible(true);
	}

	public AL(String title) {

		super(title);
		setLayout(new FlowLayout());
		addWindowListener(this);
		b = new Button("Click me");
		add(b);
		add(text);
		b.addActionListener(this);
	}

	public void actionPerformed(ActionEvent e) {
		numClicks++;
		text.setText("Button Clicked " + numClicks + " times");
	}

	public void windowClosing(WindowEvent e) {
		dispose();
		System.exit(0);
	}

	public void windowOpened(WindowEvent e) {}
	public void windowActivated(WindowEvent e) {}
	public void windowIconified(WindowEvent e) {}
	public void windowDeiconified(WindowEvent e) {}
	public void windowDeactivated(WindowEvent e) {}
	public void windowClosed(WindowEvent e) {}

}




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