Android中实现物体在屏幕的移动

程序效果是：在屏幕上画一个圆，可以用鼠标任意移动到屏幕上任何一个地方：

Java代码

1. packagecom.ray.view;
3. importandroid.app.Activity;
4. importandroid.content.Context;
5. importandroid.graphics.Canvas;
6. importandroid.graphics.Color;
7. importandroid.graphics.Paint;
8. importandroid.os.Bundle;
9. importandroid.view.MotionEvent;
10. importandroid.view.View;
11. importandroid.view.Window;
12. importandroid.view.WindowManager;
14. publicclassTestViewextendsActivity{
15. floatx=0;
16. floaty=0;
17. ViewmyView;
18. @Override
19. publicvoidonCreate(BundlesavedInstanceState){
20. super.onCreate(savedInstanceState);
21. //值得一提的是，由于画圆参照的坐标系(以系统信息栏的左下侧为原点)
22. //和MotionEvent获取的x,y坐标参照(以屏幕坐上角为原点)的坐标系不同，
23. //如果不设置全屏的话，会出现鼠标中心跟圆心不一致的情况。
24. requestWindowFeature(Window.FEATURE_NO_TITLE);
25. getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
26. myView=newMyView(this);
27. setContentView(myView);
28. }
29. publicbooleanonTouchEvent(MotionEventevent){
30. x=event.getX();
31. y=event.getY();
32. switch(event.getAction()){
33. caseMotionEvent.ACTION_DOWN:
34. myView.invalidate();
35. break;
36. caseMotionEvent.ACTION_UP:
37. myView.invalidate();
38. break;
39. caseMotionEvent.ACTION_MOVE:
40. myView.invalidate();
41. break;
42. }
43. returnsuper.onTouchEvent(event);
44. }
45. classMyViewextendsView{
46. protectedvoidonDraw(Canvascanvas){
47. PaintmPaint=newPaint();
49. mPaint.setColor(Color.BLUE);
50. mPaint.setAntiAlias(true);
51. canvas.drawCircle(x,y,20,mPaint);
52. super.onDraw(canvas);
53. }
55. publicMyView(Contextcontext){
56. super(context);
57. }
60. }
61. }