Java Never Ends - Absolute Java - page 1083

Display 19.1 Nonresponsive GUI (part 2 of 3)

26 public FillDemo()
27 {
28 setSize(WIDTH, HEIGHT);
29 setTitle("FillDemo");
30 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
31 setLayout( new BorderLayout());
32 box = new JPanel();
33 add(box, "Center");

34 JPanel buttonPanel = new JPanel();
35 buttonPanel.setLayout( new FlowLayout());
36 JButton startButton = new JButton("Start");
37 startButton.addActionListener( this );
38 buttonPanel.add(startButton);
39 add(buttonPanel, "South");
40 }

41 public void actionPerformed(ActionEvent e)
42 {
43 fill( );
44 }

Nothing else can happen until
actionPerformed returns, which
does not happen until fill returns.

45 public void fill()
46 {
47 Graphics g = box.getGraphics();

48 for ( int y = 0; y < FILL_HEIGHT; y = y + CIRCLE_SIZE)
49 for ( int x = 0; x < FILL_WIDTH; x = x + CIRCLE_SIZE)
50 {
51 g.fillOval(x, y, CIRCLE_SIZE, CIRCLE_SIZE);
52 doNothing(PAUSE);
53 }
54 }

Everything stops for
100 milliseconds
(1/10 of a second).

55 public void doNothing( int milliseconds)
56 {
57 try
58 {
59 Thread.sleep(milliseconds);
60 }
61 catch(InterruptedException e)
62 {
63 System.out.println("Unexpected interrupt");
64 System.exit(0);
65 }
66 }
67 }

(continued)