Swing Hacks

298

|

Chapter 8, Rendering

#58 Block a Window Without a Modal Dialog

HACK

Before setting the component to visible, you should save the current mouse

image and then change it to a busy cursor. The cursor will only be in effect

over the component you call

setCursor( )

on, so only the blocked window

will get the busy signal. All other windows will still use their normal cur-

sors. When

unblock( )

is called, you can restore the cursor and hide the

WindowBlocker

component again.

Build a Test Process

To test the window blocker, you will need some sort of long-running pro-

cess. The class in Example 8-4,

LongProcess

, will start a 10-second count-

down when its

actionPerformed( )

method is called. It will also print the

current time left in a status label. Note that the call to

setText( )

on the sta-

tus label is inside of a

SwingUtilities.invokeLater( ) method. This makes

sure that

setText( ) is called from the Swing event thread, avoiding any

threading issues or deadlock.

Example 8-4. Filling up clock cycles

class LongProcess implements ActionListener, Runnable {

JLabel status;

WindowBlocker blocker;

public LongProcess(JLabel status, WindowBlocker blocker) {

this.blocker = blocker;

this.status = status;

}

public void actionPerformed(ActionEvent evt) {

blocker.block( );

new Thread(this).start( );

}

public void setText(final String text) {

SwingUtilities.invokeLater(new Runnable( ) {

public void run( ) {

status.setText(text);

}

});

}

public void run( ) {

for(int i=10; i>0; i--) {

// set the label

final String text = "("+i+") seconds left";

setText(text);