1 // File: DrawCanvas.java
2
3 import java.awt.*;
4 import java.awt.event.*;
5 import java.applet.*;
6
7 public class DrawCanvas
8 extends Canvas
9 {
10
11 Graphics g;
12 String curMode="Rect";
13 mPoint curObj;
14 public boolean fill=true;
15 mPoint objList[]=new mPoint[100];
16 int index=0;
17
18
19 public DrawCanvas() {
20
21 setBackground(Color.blue);
22 setForeground(Color.yellow);
23
24 // Notice the construction of two listener objects, ourMouseListener
25 // and ourMotionListener. Both are constructed from the class
26 // definitions, called anonymous classes.
27
28 // "You should consider using an anonymous class instead of
29 // [a top level class or] a local class if:
30 // . The class has a very short body.
31 // . Only one instance of the class is needed.
32 // . The class is used right after it is defined.
33 // . The name of the class does not make your code any easier to understand."
34 // [Java in a Nutshell, pg. 119]
35
36 // We define our version of mouse adapters here
37 // because we will not use all of the MouseListener methods.
38
39 // MouseListener is an interface and all of its methods are defined abstract.
40 // This forces us to overwrite all the methods even though we do not need some.
41 // To overcome this problem, adapter classes are developed. These are
42 // classes implementing interfaces with empty method bodies. Hence, we only
43 // overwrite those methods that we need.
44
45 // In this case, we need mousePressed and mouseReleased.
46 MouseListener ourMouseListener = new MouseAdapter() {
47 // from MouseAdapter
48 public void mousePressed(MouseEvent e) {
49 int x=e.getX();
50 int y=e.getY();
51 if (curMode.equals("Rect")) curObj=new mRectangle(x, y, x, y);
52 else if (curMode.equals("Circ")) curObj=new mCircle(x, y, x, y);
53 else if (curMode.equals("Line")) curObj=new mLine(x, y, x+1, y+1);
54 else if (curMode.equals("Round")) curObj=new mRound(x, y, x, y);
55 }
56
57 // from MouseAdapter
58 public void mouseReleased(MouseEvent e) {
59 g=getGraphics();
60 g.setPaintMode();
61 curObj.setEnds(e.getX(), e.getY());
62 curObj.setFill(fill);
63 objList[index++]=curObj;
64 curObj.draw(g);
65 if(index>=100) index=100;
66 }
67 };
68
69 // We also need mouseDragged from MouseMotionListener.
70 MouseMotionListener ourMotionListener = new MouseMotionAdapter() {
71 public void mouseDragged(MouseEvent e) {
72 g=getGraphics();
73 g.setXORMode(Color.black);
74 curObj.draw(g);
75 curObj.setEnds(e.getX(), e.getY());
76 curObj.draw(g);
77 }
78 };
79
80 addMouseListener( ourMouseListener );
81 addMouseMotionListener( ourMotionListener );
82 }
83
84 public void setDrawMode(String s) {
85 if(s.equals("Clear")) {
86 index=0;
87 repaint();
88 }
89 else if(s.equals("Redraw")) repaint();
90 else curMode=s;
91 }
92
93 public void paint(Graphics g) {
94
95 g.setColor(Color.yellow);
96 super.paint(g);
97 for(int i=0; i<index; i++)
98 objList[i].draw(g);
99 }
100 }
101
102 class mPoint {
103
104
105 int x,y,x2,y2;
106 boolean fill=false;
107
108 public mPoint(int _x, int _y, int _x2, int _y2) {
109
110 x=_x;
111 y=_y;
112 x2=_x2;
113 y2=_y2;
114 };
115
116 public void draw(Graphics g) {
117 }
118
119 public void setFill(boolean _fill) {
120 fill=_fill;
121 }
122
123 public boolean isIn(int _x, int _y) {
124 return _x == x && _y == y;
125 }
126
127 public void setEnds(int _x, int _y) {
128 x2=_x;
129 y2=_y;
130 }
131 }
132
133 class mLine extends mPoint {
134
135 public mLine(int _x, int _y, int _x2, int _y2) {
136 super(_x, _y, _x2, _y2);
137 };
138
139 public void draw(Graphics g) {
140 g.drawLine(x, y, x2, y2);
141 }
142 }
143
144 class mRectangle extends mPoint {
145
146 public mRectangle(int _x, int _y, int _x2, int _y2) {
147 super(_x, _y, _x2, _y2);
148 };
149
150 public void draw(Graphics g) {
151 if (fill) {
152 g.setColor(Color.black);
153 g.fillRect(x, y, x2-x, y2-y);
154 g.setColor(Color.yellow);
155 }
156 g.drawRect(x, y, x2-x, y2-y);
157 }
158
159 public boolean isIn(int _x, int _y) {
160 Rectangle r=new Rectangle(x, y, x2-x, y2-y);
161 return r.inside(_x, _y);
162 }
163 }
164
165 class mRound extends mRectangle {
166
167 public mRound(int _x, int _y, int _x2, int _y2) {
168 super(_x, _y, _x2, _y2);
169 };
170
171 public void draw(Graphics g) {
172 if (fill) {
173 g.setColor(Color.black);
174 g.fillRoundRect(x, y, x2-x, y2-y, 100, 50);
175 g.setColor(Color.yellow);
176 }
177 g.drawRoundRect(x, y, x2-x, y2-y, 100, 50);
178 }
179 }
180
181 class mCircle extends mRectangle {
182
183 public mCircle(int _x, int _y, int _x2, int _y2) {
184 super(_x, _y, _x2, _y2);
185 };
186
187 public void draw(Graphics g) {
188 if (fill) {
189 g.setColor(Color.black);
190 g.fillOval(x, y, x2-x, y2-y);
191 g.setColor(Color.yellow);
192 }
193 g.drawOval(x, y, x2-x, y2-y);
194 }
195 }
196
197