1 /*
2 * File: mAdapterApplet.java
3 *
4 * MouseEvents, movable objects, and adapter classes
5 *
6 * Note: The private modifier was removed from some of the
7 * variables so that the adapter class has access.
8 */
9
10 import java.applet.*;
11 import java.awt.*;
12 import java.awt.event.*;
13
14 public class mAdapterApplet extends Applet
15 implements MouseMotionListener {
16
17 // Instance variables:
18 private int numObj = 3; // number of movable objects
19 mPoint object[]; // array of movable objects
20 private Image buffer; // image object for double buffering
21 private Graphics gOffScreen; // graphics object for double buffering
22
23 // Mouse handling variables:
24 int current = -1;
25 int hit = -1;
26 int xoffset = 0;
27 int yoffset = 0;
28
29 // Colors:
30 private Color objColor = Color.cyan;
31 private Color objColorSelect = Color.red;
32 private Color bgColor = Color.black;
33 private Color fgColor = Color.white;
34
35 public void init() {
36 setBackground( bgColor );
37 setForeground( fgColor );
38
39 // Instantiate object array:
40 object = new mPoint[ numObj ];
41
42 // Instantiate a rectangle:
43 object[0] = new mRectangle( 10, 10, 100, 100 );
44 object[0].setColor( objColor );
45
46 // Instantiate a circle:
47 object[1] = new mOval( 200, 10, 100, 100 );
48 object[1].setColor( objColor );
49
50 // Instantiate a triangle:
51 object[2] = new mTriangle( 10, 200, 100, 100 );
52 object[2].setColor( objColor );
53
54 // Create an off-screen image for double buffering:
55 buffer = createImage( getSize().width, getSize().height );
56 // Get off-screen graphics context:
57 gOffScreen = buffer.getGraphics();
58
59 // Register the applet to listen for ALL mouse events:
60 this.addMouseListener( new MouseHandler( this ) );
61 this.addMouseMotionListener( this );
62 }
63
64 // Override java.awt.Component.update:
65 public void update( Graphics g ) {
66 // Fill background:
67 gOffScreen.setColor( getBackground() );
68 gOffScreen.fillRect( 1, 1, getSize().width - 2, getSize().height - 2 );
69 // Draw boundary:
70 gOffScreen.setColor( getForeground() );
71 gOffScreen.drawRect( 0, 0, getSize().width - 1, getSize().height - 1 );
72 paint( gOffScreen );
73
74 // Draw the buffer in the applet window:
75 g.drawImage( buffer, 0, 0, this );
76 }
77
78 // Override java.awt.Component.paint:
79 public void paint( Graphics g ) {
80 // Paint each object:
81 for ( int i = 0; i < numObj; i++ ) {
82 object[i].paint(g);
83 }
84 }
85
86 /*
87 * MouseMotionListener event handlers
88 */
89
90 public void mouseMoved( MouseEvent e ) {
91 hit = -1;
92 for ( int i = 0; i < numObj; i++ ) {
93 if ( object[i].isInside( e.getX(), e.getY() ) ) {
94 hit = i; break;
95 }
96 }
97
98 for ( int i = 0; i < numObj; i++ ) {
99 object[i].setColor( (i == hit) ? objColorSelect : objColor );
100 }
101 repaint();
102 }
103
104 public void mouseDragged( MouseEvent e ) {
105 if ( current != -1 ) {
106 int x = e.getX() + xoffset;
107 int y = e.getY() + yoffset;
108 object[current].setPoint( x, y );
109 repaint();
110 }
111 }
112
113 }
114
115 // Extend the MouseAdapter class, which is a trivial implementation
116 // of the MouseListener interface:
117 class MouseHandler extends MouseAdapter {
118
119 private mAdapterApplet applet;
120
121 public MouseHandler( mAdapterApplet a ) { applet = a; }
122
123 public void mousePressed( MouseEvent e ) {
124 int i = applet.current = applet.hit;
125 if ( i != -1 ) {
126 applet.xoffset = applet.object[i].getX() - e.getX();
127 applet.yoffset = applet.object[i].getY() - e.getY();
128 }
129 }
130
131 public void mouseReleased( MouseEvent e ) {
132 applet.current = -1;
133 }
134
135 }
136