Swing Hacks

Display a Busy Cursor #88

Chapter 12, Miscellany

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445

HACK

Like most run( ) methods, the previous code does something repeatedly in a

loop with a

sleep( ) on each pass. In this case, you call setCursor( ) on the

frame and increment the count variable. Notice the code line:

cursors[count % cursors.length]

which will loop over each cursor in the array, wrapping when it reaches the

end. The mod operator (

%) is indispensable for these types of calculations.

The loop also sleeps on every pass. I chose 200 ms because that lets the

cursor make a complete revolution every second and a half, which seemed

about right; you can adjust it to your taste:

public void actionPerformed(ActionEvent evt) {

JButton button = (JButton)evt.getSource( );

if(animate) {

button.setText("Start Animation");

animate = false;

} else {

animate = true;

button.setText("Stop Animation");

new Thread(this).start( );

}

}

The actionPerformed( ) method starts and stops the animation thread. It

also updates the text on the

JButton as further user feedback.

Put It All Together

public static void main(String[] args) {

JFrame frame = new JFrame("Animated Cursor Hack");

JButton button = new JButton("Start Animation");

button.addActionListener(new AnimatedCursor(frame));

frame.getContentPane( ).add(button);

frame.pack( );

frame.show( );

}

The main( ) method in the preceding code creates a frame with a control but-

ton. The

AnimatedCursor applies directly to the frame so that the cursor will

animate whenever it’s over the window. A screen capture cannot really cap-

ture the effect, but when you put it together, it will look something like

Figure 12-1.