Event Handling with the Swing Component Set - The Definitive Guide to Java Swing - page 21

To demonstrate the proper way to create a Swing-based program, Listing 2-1 shows the
source for a selectable button.
Listing 2-1. Swing Application Framework
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ButtonSample {
public static void main(String args[]) {
Runnable runner = new Runnable() {
public void run() {
JFrame frame = new JFrame("Button Sample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton button = new JButton("Select Me");
// Define ActionListener
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
System.out.println("I was selected.");
}
};
// Attach listeners
button.addActionListener(actionListener);
frame.add(button, BorderLayout.SOUTH);
frame.setSize(300, 100);
frame.setVisible(true);
}
};
EventQueue.invokeLater(runner);
}
}
This code produces the button shown in Figure 2-3.
Figure 2-3. Button sample
First, let's look at the invokeLater() method. It requires a Runnable object as its argument.
You just create a Runnable object and pass it along to the invokeLater() method. Some time
after the current event dispatching is done, this Runnable object will execute.