[转] android 多点触摸 实现图片缩放 Image Zoom

1. import android.graphics.Matrix;   
2. import android.graphics.PointF;   
3. import android.util.FloatMath;   
4. import android.view.MotionEvent;   
5. import android.view.View;   
6. import android.view.View.OnTouchListener;   
7. import android.widget.ImageView;   
8. public class MulitPointTouchListener implements OnTouchListener {   
9.         Matrix matrix = new Matrix();   
10.         Matrix savedMatrix = new Matrix();   
11.         static final int NONE = 0;   
12.         static final int DRAG = 1;   
13.         static final int ZOOM = 2;   
14.         int mode = NONE;   
15.         PointF start = new PointF();   
16.         PointF mid = new PointF();   
17.         float oldDist = 1f;   
18.         @Override   
19.         public boolean onTouch(View v, MotionEvent event) {   
20.                 ImageView view = (ImageView) v;   
21.                 switch (event.getAction() & MotionEvent.ACTION_MASK) {   
22.                 case MotionEvent.ACTION_DOWN:   
23.                         matrix.set(view.getImageMatrix());   
24.                         savedMatrix.set(matrix);   
25.                         start.set(event.getX(), event.getY());   
26.                         mode = DRAG;   
27.                          
28.                         break;   
29.                 case MotionEvent.ACTION_POINTER_DOWN:   
30.                         oldDist = spacing(event);   
31.                         if (oldDist > 10f) {   
32.                                 savedMatrix.set(matrix);   
33.                                 midPoint(mid, event);   
34.                                 mode = ZOOM;   
35.                         }   
36.                         break;   
37.                 case MotionEvent.ACTION_UP:   
38.                 case MotionEvent.ACTION_POINTER_UP:   
39.                         mode = NONE;   
40.                         break;   
41.                 case MotionEvent.ACTION_MOVE:   
42.                         if (mode == DRAG) {   
43.                                 matrix.set(savedMatrix);   
44.                                 matrix.postTranslate(event.getX() - start.x, event.getY()   
45.                                                 - start.y);   
46.                         } else if (mode == ZOOM) {   
47.                                 float newDist = spacing(event);   
48.                                 if (newDist > 10f) {   
49.                                         matrix.set(savedMatrix);   
50.                                         float scale = newDist / oldDist;   
51.                                         matrix.postScale(scale, scale, mid.x, mid.y);   
52.                                 }   
53.                         }   
54.                         break;   
55.                 }   
56.                 view.setImageMatrix(matrix);   
57.                 return true;   
58.         }   
59.           
60.          
61.         private float spacing(MotionEvent event) {   
62.                 float x = event.getX(0) - event.getX(1);   
63.                 float y = event.getY(0) - event.getY(1);   
64.                 return FloatMath.sqrt(x * x + y * y);   
65.         }   
66.          
67.         private void midPoint(PointF point, MotionEvent event) {   
68.                 float x = event.getX(0) + event.getX(1);   
69.                 float y = event.getY(0) + event.getY(1);   
70.                 point.set(x / 2, y / 2);   
71.         }   
72. }   
73. imageView.setOnTouchListener(new MulitPointTouchListener ());在xml中要将图片的缩放格式改成Matrix   
74.   
75. 注：android:scaleType="matrix"   
76. 注：此文档为转载