Android之实现手势缩放ImageView

将以下代码写到MulitPointTouchListener.java中，然后对你相应的图片进行OnTouchListener。
例如：imageView.setOnTouchListener(new MulitPointTouchListener ());

在xml中要将ImageView的缩放格式改成Matrix

例如：android:scaleType="matrix"

这样就可以实现图片的缩放了

 

下面是MulitPointTouchListener.java代码：

1. public class MulitPointTouchListener implements OnTouchListener {     
2.         private static final String TAG = "Touch";     
3.         // These matrices will be used to move and zoom image     
4.         Matrix matrix = new Matrix();     
5.         Matrix savedMatrix = new Matrix();     
6.     
7.         // We can be in one of these 3 states     
8.         static final int NONE = 0;     
9.         static final int DRAG = 1;     
10.         static final int ZOOM = 2;     
11.         int mode = NONE;     
12.     
13.         // Remember some things for zooming     
14.         PointF start = new PointF();     
15.         PointF mid = new PointF();     
16.         float oldDist = 1f;     
17.     
18.         @Override    
19.         public boolean onTouch(View v, MotionEvent event) {     
20.     
21.                 ImageView view = (ImageView) v;     
22.                 // Log.e("view_width",     
23.                 // view.getImageMatrix()..toString()+"*"+v.getWidth());     
24.                 // Dump touch event to log     
25.                 dumpEvent(event);     
26.     
27.                 // Handle touch events here...     
28.                 switch (event.getAction() & MotionEvent.ACTION_MASK) {     
29.                 case MotionEvent.ACTION_DOWN:     
30.     
31.                         matrix.set(view.getImageMatrix());     
32.                         savedMatrix.set(matrix);     
33.                         start.set(event.getX(), event.getY());     
34.                         //Log.d(TAG, "mode=DRAG");     
35.                         mode = DRAG;     
36.     
37.                             
38.                         //Log.d(TAG, "mode=NONE");     
39.                         break;     
40.                 case MotionEvent.ACTION_POINTER_DOWN:     
41.                         oldDist = spacing(event);     
42.                         //Log.d(TAG, "oldDist=" + oldDist);     
43.                         if (oldDist > 10f) {     
44.                                 savedMatrix.set(matrix);     
45.                                 midPoint(mid, event);     
46.                                 mode = ZOOM;     
47.                                 //Log.d(TAG, "mode=ZOOM");     
48.                         }     
49.                         break;     
50.                 case MotionEvent.ACTION_UP:     
51.                 case MotionEvent.ACTION_POINTER_UP:     
52.                         mode = NONE;     
53.                         //Log.e("view.getWidth", view.getWidth() + "");     
54.                         //Log.e("view.getHeight", view.getHeight() + "");     
55.     
56.                         break;     
57.                 case MotionEvent.ACTION_MOVE:     
58.                         if (mode == DRAG) {     
59.                                 // ...     
60.                                 matrix.set(savedMatrix);     
61.                                 matrix.postTranslate(event.getX() - start.x, event.getY()     
62.                                                 - start.y);     
63.                         } else if (mode == ZOOM) {     
64.                                 float newDist = spacing(event);     
65.                                 //Log.d(TAG, "newDist=" + newDist);     
66.                                 if (newDist > 10f) {     
67.                                         matrix.set(savedMatrix);     
68.                                         float scale = newDist / oldDist;     
69.                                         matrix.postScale(scale, scale, mid.x, mid.y);     
70.                                 }     
71.                         }     
72.                         break;     
73.                 }     
74.     
75.                 view.setImageMatrix(matrix);     
76.                 return true; // indicate event was handled     
77.         }     
78.     
79.         private void dumpEvent(MotionEvent event) {     
80.                 String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",     
81.                                 "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };     
82.                 StringBuilder sb = new StringBuilder();     
83.                 int action = event.getAction();     
84.                 int actionCode = action & MotionEvent.ACTION_MASK;     
85.                 sb.append("event ACTION_").append(names[actionCode]);     
86.                 if (actionCode == MotionEvent.ACTION_POINTER_DOWN     
87.                                 || actionCode == MotionEvent.ACTION_POINTER_UP) {     
88.                         sb.append("(pid ").append(     
89.                                         action >> MotionEvent.ACTION_POINTER_ID_SHIFT);     
90.                         sb.append(")");     
91.                 }     
92.                 sb.append("[");     
93.                 for (int i = 0; i < event.getPointerCount(); i++) {     
94.                         sb.append("#").append(i);     
95.                         sb.append("(pid ").append(event.getPointerId(i));     
96.                         sb.append(")=").append((int) event.getX(i));     
97.                         sb.append(",").append((int) event.getY(i));     
98.                         if (i + 1 < event.getPointerCount())     
99.                                 sb.append(";");     
100.                 }     
101.                 sb.append("]");     
102.                 //Log.d(TAG, sb.toString());     
103.         }     
104.     
105.             
106.         private float spacing(MotionEvent event) {     
107.                 float x = event.getX(0) - event.getX(1);     
108.                 float y = event.getY(0) - event.getY(1);     
109.                 return FloatMath.sqrt(x * x + y * y);     
110.         }     
111.     
112.             
113.         private void midPoint(PointF point, MotionEvent event) {     
114.                 float x = event.getX(0) + event.getX(1);     
115.                 float y = event.getY(0) + event.getY(1);     
116.                 point.set(x / 2, y / 2);     
117.         }     
118. }