android多点触控统一的原理(使用 event.getAction()&MotionEvent.ACTION_MASK的原因)

android多点触控统一的原理(使用 event.getAction()&MotionEvent.ACTION_MASK的原因)

2014-08-15 11:55  3662人阅读  评论(0)  收藏  举报

  分类：

 

Android（183） 

看到下面代码中用了AND位运算是为了什么呢？

public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: showMsg("ACTION_DOWN" + action); break; case MotionEvent.ACTION_UP: showMsg("ACTION_UP" + action); break; case MotionEvent.ACTION_POINTER_UP: showMsg("ACTION_POINTER_UP" + action); break; case MotionEvent.ACTION_POINTER_DOWN: showMsg("ACTION_POINTER_DOWN" + action); break; } return super.onTouchEvent(event); }

首先来看看这些常量的值

ACTION_MASK     0x000000ff ACTION_DOWN     0x00000000         ACTION_UP      0x00000001        ACTION_MOVE      0x00000002 ACTION_POINTER_DOWN       0x00000005            ACTION_POINTER_UP        0x00000006 ACTION_POINTER_1_DOWN     0x00000005            ACTION_POINTER_1_UP      0x00000006 ACTION_POINTER_2_DOWN     0x00000105            ACTION_POINTER_2_UP      0x00000106

例如：ACTION_MASK & ACTION_POINTER_2_DOWN 即0x000000ff & 0×00000105=0x0000005

可以看到，and运算的结果总是小于等于0x000000ff，那就是说and之后，无论你多少根手指加进来，都是会ACTION_POINTER_DOWN或者ACTION_POINTER_UP

[java]  view plain  copy

 

1. imgitem.setOnTouchListener(new OnTouchListener() {  
2.   
3.                         PointF start = new PointF();  
4.                         PointF mid = new PointF();  
5.                         float oldDist = 1f;  
6.                         Matrix matrix = new Matrix();  
7.                         Matrix savedMatrix = new Matrix();  
8.                         static final int NONE = 0;  
9.                         static final int DRAG = 1;  
10.                         static final int ZOOM = 2;  
11.                         int mode = NONE;  
12.   
13.                         long startTime;  
14.   
15.                         public boolean onTouch(View v, MotionEvent event) {  
16.                             ImageView view = (ImageView) v;  
17.                             view.setScaleType(ScaleType.MATRIX);  
18.   
19.                             switch (event.getAction() & MotionEvent.ACTION_MASK) {  
20.   
21.                             case MotionEvent.ACTION_DOWN:  
22.                                 matrix.set(view.getImageMatrix());  
23.                                 savedMatrix.set(matrix);  
24.                                 start.set(event.getX(), event.getY());  
25.                                 mode = DRAG;  
26.                                 // isclick = true;  
27.                                 startTime = System.currentTimeMillis();  
28.                                 break;  
29.   
30.                             case MotionEvent.ACTION_POINTER_DOWN:  
31.                                 // isclick = false;  
32.                                 oldDist = spacing(event);  
33.                                 if (oldDist > 10f) {  
34.                                     savedMatrix.set(matrix);  
35.                                     midPoint(mid, event);  
36.                                     mode = ZOOM;  
37.                                 }  
38.                                 break;  
39.   
40.                             case MotionEvent.ACTION_UP:  
41.                                 /*if (mode == DRAG && System.currentTimeMillis() - startTime < 150) { 
42.                                     finish(); 
43.                                     overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out); 
44.                                 }*/  
45.                                 break;  
46.                             case MotionEvent.ACTION_POINTER_UP:  
47.                                 mode = NONE;  
48.                                 break;  
49.                             case MotionEvent.ACTION_MOVE:  
50.                                 // isclick = false;  
51.                                 if (mode == DRAG) {  
52.                                     matrix.set(savedMatrix);  
53.                                     matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);  
54.                                 } else if (mode == ZOOM) {  
55.                                     float newDist = spacing(event);  
56.                                     if (newDist > 10f) {  
57.                                         matrix.set(savedMatrix);  
58.                                         float scale = newDist / oldDist;  
59.                                         matrix.postScale(scale, scale, mid.x, mid.y);  
60.                                     }  
61.                                 }  
62.                                 break;  
63.                             }  
64.   
65.                             view.setImageMatrix(matrix);  
66.   
67.                             return true;  
68.                         }  
69.   
70.                         private float spacing(MotionEvent event) {  
71.                             float x = event.getX(0) - event.getX(1);  
72.                             float y = event.getY(0) - event.getY(1);  
73.                             return FloatMath.sqrt(x * x + y * y);  
74.                         }  
75.   
76.                         private void midPoint(PointF point, MotionEvent event) {  
77.                             float x = event.getX(0) + event.getX(1);  
78.                             float y = event.getY(0) + event.getY(1);  
79.                             point.set(x / 2, y / 2);  
80.                         }  
81.   
82.                     });  

看到下面代码中用了AND位运算是为了什么呢？

public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: showMsg("ACTION_DOWN" + action); break; case MotionEvent.ACTION_UP: showMsg("ACTION_UP" + action); break; case MotionEvent.ACTION_POINTER_UP: showMsg("ACTION_POINTER_UP" + action); break; case MotionEvent.ACTION_POINTER_DOWN: showMsg("ACTION_POINTER_DOWN" + action); break; } return super.onTouchEvent(event); }

首先来看看这些常量的值

ACTION_MASK     0x000000ff ACTION_DOWN     0x00000000         ACTION_UP      0x00000001        ACTION_MOVE      0x00000002 ACTION_POINTER_DOWN       0x00000005            ACTION_POINTER_UP        0x00000006 ACTION_POINTER_1_DOWN     0x00000005            ACTION_POINTER_1_UP      0x00000006 ACTION_POINTER_2_DOWN     0x00000105            ACTION_POINTER_2_UP      0x00000106

例如：ACTION_MASK & ACTION_POINTER_2_DOWN 即0x000000ff & 0×00000105=0x0000005

可以看到，and运算的结果总是小于等于0x000000ff，那就是说and之后，无论你多少根手指加进来，都是会ACTION_POINTER_DOWN或者ACTION_POINTER_UP

[java]  view plain  copy

 

1. imgitem.setOnTouchListener(new OnTouchListener() {  
2.   
3.                         PointF start = new PointF();  
4.                         PointF mid = new PointF();  
5.                         float oldDist = 1f;  
6.                         Matrix matrix = new Matrix();  
7.                         Matrix savedMatrix = new Matrix();  
8.                         static final int NONE = 0;  
9.                         static final int DRAG = 1;  
10.                         static final int ZOOM = 2;  
11.                         int mode = NONE;  
12.   
13.                         long startTime;  
14.   
15.                         public boolean onTouch(View v, MotionEvent event) {  
16.                             ImageView view = (ImageView) v;  
17.                             view.setScaleType(ScaleType.MATRIX);  
18.   
19.                             switch (event.getAction() & MotionEvent.ACTION_MASK) {  
20.   
21.                             case MotionEvent.ACTION_DOWN:  
22.                                 matrix.set(view.getImageMatrix());  
23.                                 savedMatrix.set(matrix);  
24.                                 start.set(event.getX(), event.getY());  
25.                                 mode = DRAG;  
26.                                 // isclick = true;  
27.                                 startTime = System.currentTimeMillis();  
28.                                 break;  
29.   
30.                             case MotionEvent.ACTION_POINTER_DOWN:  
31.                                 // isclick = false;  
32.                                 oldDist = spacing(event);  
33.                                 if (oldDist > 10f) {  
34.                                     savedMatrix.set(matrix);  
35.                                     midPoint(mid, event);  
36.                                     mode = ZOOM;  
37.                                 }  
38.                                 break;  
39.   
40.                             case MotionEvent.ACTION_UP:  
41.                                 /*if (mode == DRAG && System.currentTimeMillis() - startTime < 150) { 
42.                                     finish(); 
43.                                     overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out); 
44.                                 }*/  
45.                                 break;  
46.                             case MotionEvent.ACTION_POINTER_UP:  
47.                                 mode = NONE;  
48.                                 break;  
49.                             case MotionEvent.ACTION_MOVE:  
50.                                 // isclick = false;  
51.                                 if (mode == DRAG) {  
52.                                     matrix.set(savedMatrix);  
53.                                     matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);  
54.                                 } else if (mode == ZOOM) {  
55.                                     float newDist = spacing(event);  
56.                                     if (newDist > 10f) {  
57.                                         matrix.set(savedMatrix);  
58.                                         float scale = newDist / oldDist;  
59.                                         matrix.postScale(scale, scale, mid.x, mid.y);  
60.                                     }  
61.                                 }  
62.                                 break;  
63.                             }  
64.   
65.                             view.setImageMatrix(matrix);  
66.   
67.                             return true;  
68.                         }  
69.   
70.                         private float spacing(MotionEvent event) {  
71.                             float x = event.getX(0) - event.getX(1);  
72.                             float y = event.getY(0) - event.getY(1);  
73.                             return FloatMath.sqrt(x * x + y * y);  
74.                         }  
75.   
76.                         private void midPoint(PointF point, MotionEvent event) {  
77.                             float x = event.getX(0) + event.getX(1);  
78.                             float y = event.getY(0) + event.getY(1);  
79.                             point.set(x / 2, y / 2);  
80.                         }  
81.   
82.                     });