1 public class GameView extends View  {
 2     //    声明Paint对象
 3     private Paint mPaint = null;
 4     private int StrokeWidth = 5;
 5     private Rect rect = new Rect(0,0,0,0);//手动绘制矩形
 6
 7     public GameView(Context context){
 8         super(context);
 9         //构建对象
10         mPaint = new Paint();
11         mPaint.setColor(Color.RED);
12         //开启线程
13        // new Thread(this).start();
14     }
15     @Override
16     protected void onDraw(Canvas canvas) {
17         super.onDraw(canvas);
18         //设置无锯齿
19         mPaint.setAntiAlias(true);
20         canvas.drawARGB(50,255,227,0);
21         mPaint.setStyle(Paint.Style.STROKE);
22         mPaint.setStrokeWidth(StrokeWidth);
23         mPaint.setColor(Color.GREEN);
24         mPaint.setAlpha(100);
25         // 绘制绿色实心矩形
26         canvas.drawRect(100, 200, 400, 200 + 400, mPaint);
27         mPaint.setColor(Color.RED);
28         canvas.drawRect(rect,mPaint);
29     }
30     @Override
31     public boolean onTouchEvent(MotionEvent event) {
32         int x = (int)event.getX();
33         int y = (int)event.getY();
34         switch (event.getAction()){
35             case MotionEvent.ACTION_DOWN:
36                 rect.right+=StrokeWidth;
37                 rect.bottom+=StrokeWidth;
38                 invalidate(rect);
39                 rect.left = x;
40                 rect.top = y;
41                 rect.right =rect.left;
42                 rect.bottom = rect.top;
43
44             case MotionEvent.ACTION_MOVE:
45                 Rect old =
46                 new Rect(rect.left,rect.top,rect.right+StrokeWidth,rect.bottom+StrokeWidth);
47                 rect.right = x;
48                 rect.bottom = y;
49                 old.union(x,y);
50                 invalidate(old);
51                 break;
52
53             case MotionEvent.ACTION_UP:
54                 break;
55             default:
56                 break;
57         }
58         return  true;//处理了触摸信息，消息不再传递
59     }
60
61 }

1         super.onCreate(savedInstanceState);
2         setContentView(R.layout.activity_main);
3
4         gameView = new GameView(this);
5         addContentView(gameView);        

Rect old = new Rect(rect.left,rect.top,rect.right+StrokeWidth,rect.bottom+StrokeWidth);