// import略   public class ImageViewerActivity extends Activity implements OnTouchListener {      private ImageView mImageView;      private Matrix matrix = new Matrix();      private Matrix savedMatrix = new Matrix();      private static final int NONE = 0;      private static final int DRAG = 1;      private static final int ZOOM = 2;      private int mode = NONE;      // 第一个按下的手指的点       private PointF startPoint = new PointF();      // 两个按下的手指的触摸点的中点       private PointF midPoint = new PointF();      // 初始的两个手指按下的触摸点的距离       private float oriDis = 1f;      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          this.setContentView(R.layout.imageviewer);          mImageView = (ImageView) this.findViewById(R.id.imageView);          mImageView.setOnTouchListener(this);      }      @Override      public boolean onTouch(View v, MotionEvent event) {          ImageView view = (ImageView) v;          // 进行与操作是为了判断多点触摸           switch (event.getAction() & MotionEvent.ACTION_MASK) {          case MotionEvent.ACTION_DOWN:              // 第一个手指按下事件               matrix.set(view.getImageMatrix());              savedMatrix.set(matrix);              startPoint.set(event.getX(), event.getY());              mode = DRAG;              break;          case MotionEvent.ACTION_POINTER_DOWN:              // 第二个手指按下事件               oriDis = distance(event);              if (oriDis > 10f) {                  savedMatrix.set(matrix);                  midPoint = middle(event);                  mode = ZOOM;              }              break;          case MotionEvent.ACTION_UP:          case MotionEvent.ACTION_POINTER_UP:              // 手指放开事件               mode = NONE;              break;          case MotionEvent.ACTION_MOVE:              // 手指滑动事件               if (mode == DRAG) {                  // 是一个手指拖动                   matrix.set(savedMatrix);                  matrix.postTranslate(event.getX() - startPoint.x, event.getY()                          - startPoint.y);              } else if (mode == ZOOM) {                  // 两个手指滑动                   float newDist = distance(event);                  if (newDist > 10f) {                      matrix.set(savedMatrix);                      float scale = newDist / oriDis;                      matrix.postScale(scale, scale, midPoint.x, midPoint.y);                  }              }              break;          }          // 设置ImageView的Matrix           view.setImageMatrix(matrix);          return true;      }      // 计算两个触摸点之间的距离       private float distance(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);      }      // 计算两个触摸点的中点       private PointF middle(MotionEvent event) {          float x = event.getX(0) + event.getX(1);          float y = event.getY(0) + event.getY(1);          return new PointF(x / 2, y / 2);      }  } 

<?xml version="1.0" encoding="utf-8"?>  <RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent">      <ImageView           android:id="@+id/imageView"          android:layout_width="fill_parent"          android:layout_height="fill_parent"          android:src="@drawable/example"          android:scaleType="matrix" >      </ImageView>  </RelativeLayout>