1 /*
2 * File: mObjApplet.java
3 *
4 * Double-buffered version of mRectApplet.java
5 * with boundary checking
6 */
7
8 import java.applet.*;
9 import java.awt.*;
10
11 public class mObjApplet extends Applet implements Runnable
12 {
13 // Instance variables:
14 private int numObj = 3; // number of movable objects
15 private mPoint object[]; // array of movable objects
16 private Thread thread; // a thread
17 private Image buffer; // image object for double buffering
18 private Graphics gOffScreen; // graphics object for double buffering
19
20
21 // Override java.applet.Applet.init:
22 public void init ()
23 {
24 setBackground( Color.black );
25 setForeground( Color.white );
26
27 // Instantiate object array:
28 object = new mPoint[ numObj ];
29 // Instantiate a rectangle:
30 object[0] = new mRectangle( 10, 10, 100, 100 );
31 object[0].setDelta( 2, 3 );
32 object[0].setColor( Color.red );
33 // Instantiate a circle:
34 object[1] = new mOval( 200, 10, 100, 100 );
35 object[1].setDelta( -3, 2 );
36 object[1].setColor( Color.blue );
37 // Instantiate a triangle:
38 object[2] = new mTriangle( 10, 200, 100, 100 );
39 object[2].setDelta( -2, 2 );
40 object[2].setColor( Color.green );
41
42 // Create an off-screen image for double buffering:
43 buffer = createImage( getSize().width, getSize().height );
44 // Get off-screen graphics context:
45 gOffScreen = buffer.getGraphics();
46 }
47
48 // Override java.applet.Applet.start:
49 public void start()
50 {
51 if ( thread == null )
52 { thread = new Thread( this );
53 thread.start();
54 }
55 }
56
57 // Override java.applet.Applet.stop:
58 public void stop()
59 {
60 if ( thread != null )
61 { thread.stop();
62 thread = null;
63 }
64 }
65
66 // Implement java.lang.Runnable.run:
67 public void run()
68 {
69 while ( thread != null )
70 {
71 repaint();
72 try
73 { Thread.sleep(20);
74 } catch ( InterruptedException e ) { }; // Do nothing
75 }
76 }
77
78 // Override java.awt.Component.update
79 public void update (Graphics g)
80 { paint (g);
81 }
82
83 // Override java.awt.Component.paint
84 public void paint( Graphics g )
85 {
86 // Fill background:
87 gOffScreen.setColor( getBackground() );
88 gOffScreen.fillRect( 1, 1, getSize().width - 2, getSize().height - 2 );
89
90 // move each object after checking the boundary:
91 for ( int i = 0; i < numObj; i++ )
92 {
93 object[i].checkBoundary( getBounds() );
94 object[i].move();
95 object[i].paint(gOffScreen);
96 }
97
98 // Draw the buffer in the applet window:
99 g.drawImage( buffer, 0, 0, this );
100 }
101 }
102
103