android 多点触摸 实现图片缩放 Image Zoom

import android.graphics.Matrix;   
import android.graphics.PointF;   
import android.util.FloatMath;   
import android.view.MotionEvent;   
import android.view.View;   
import android.view.View.OnTouchListener;   
import android.widget.ImageView;   
public class MulitPointTouchListener implements OnTouchListener {   
        Matrix matrix = new Matrix();   
        Matrix savedMatrix = new Matrix();   
        static final int NONE = 0;   
        static final int DRAG = 1;   
        static final int ZOOM = 2;   
        int mode = NONE;   
        PointF start = new PointF();   
        PointF mid = new PointF();   
        float oldDist = 1f;   
        @Override   
        public boolean onTouch(View v, MotionEvent event) {   
                ImageView view = (ImageView) v;   
                switch (event.getAction() & MotionEvent.ACTION_MASK) {   
                case MotionEvent.ACTION_DOWN:   
                        matrix.set(view.getImageMatrix());   
                        savedMatrix.set(matrix);   
                        start.set(event.getX(), event.getY());   
                        mode = DRAG;   
                         
                        break;   
                case MotionEvent.ACTION_POINTER_DOWN:   
                        oldDist = spacing(event);   
                        if (oldDist > 10f) {   
                                savedMatrix.set(matrix);   
                                midPoint(mid, event);   
                                mode = ZOOM;   
                        }   
                        break;   
                case MotionEvent.ACTION_UP:   
                case MotionEvent.ACTION_POINTER_UP:   
                        mode = NONE;   
                        break;   
                case MotionEvent.ACTION_MOVE:   
                        if (mode == DRAG) {   
                                matrix.set(savedMatrix);   
                                matrix.postTranslate(event.getX() - start.x, event.getY()   
                                                - start.y);   
                        } else if (mode == ZOOM) {   
                                float newDist = spacing(event);   
                                if (newDist > 10f) {   
                                        matrix.set(savedMatrix);   
                                        float scale = newDist / oldDist;   
                                        matrix.postScale(scale, scale, mid.x, mid.y);   
                                }   
                        }   
                        break;   
                }   
                view.setImageMatrix(matrix);   
                return true;   
        }   
          
         
        private float spacing(MotionEvent event) {   
                float x = event.getX(0) - event.getX(1);   
                float y = event.getY(0) - event.getY(1);   
                return FloatMath.sqrt(x * x + y * y);   
        }   
         
        private void midPoint(PointF point, MotionEvent event) {   
                float x = event.getX(0) + event.getX(1);   
                float y = event.getY(0) + event.getY(1);   
                point.set(x / 2, y / 2);   
        }   
}   
imageView.setOnTouchListener(new MulitPointTouchListener ());在xml中要将图片的缩放格式改成Matrix   
  
注：android:scaleType="matrix"   
注：此文档为转载

原文地址： http://blog.csdn.net/hundsong/article/details/6532292