Graphical User Interfaces - Java - page 556

Action Handling: Making Buttons Work

Problem

Your button doesn't do anything when the user presses it.

Solution

Add an ActionListener to do the work.

Discussion

Event listeners come in about half a dozen different types. The most common is the Ac-
tionListener , used by push buttons, text fields, and certain other components to indicate
that the user has performed a high-level action, such as activating a push button or pressing
Enter in a text field. The paradigm (shown in Figure 14-3 ) is that you create a Listener ob-
ject, register it with the event source (such as the push button), and wait. Later, when and if
the user pushes the button, the button will call your Listener .

Figure 14-3. AWT listener relationships

Here's some simple code in which pushing a button causes the program to print a friendly
message:

/** Demonstrate simple use of Button */
public

public class class ButtonDemo ButtonDemo extends extends JFrame implements implements ActionListener {

JButton b1 ;

public public ButtonDemo () {

setLayout ( new new FlowLayout ());

add ( b1 = new

new JButton ( "A button" ));