Android手势控制实现缩放、移动图片

package com.liyong.btprinter; 

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 { 

private static final String TAG = "Touch"; 
  // These matrices will be used to move and zoom image 
  Matrix matrix = new Matrix(); 
  Matrix savedMatrix = new Matrix(); 

  // We can be in one of these 3 states 
  static final int NONE = 0; 
  static final int DRAG = 1; 
  static final int ZOOM = 2; 
  int mode = NONE; 

  // Remember some things for zooming 
  PointF start = new PointF(); 
  PointF mid = new PointF(); 
  float oldDist = 1f; 

  @Override 
  public boolean onTouch(View v, MotionEvent event) { 

      ImageView view = (ImageView) v; 
      // Log.e("view_width", 
      // view.getImageMatrix()..toString()+"*"+v.getWidth()); 
      // Dump touch event to log 
      dumpEvent(event); 

      // Handle touch events here... 
      switch (event.getAction() & MotionEvent.ACTION_MASK) { 
      case MotionEvent.ACTION_DOWN: 

          matrix.set(view.getImageMatrix()); 
          savedMatrix.set(matrix); 
          start.set(event.getX(), event.getY()); 
          //Log.d(TAG, "mode=DRAG"); 
          mode = DRAG; 

          
          //Log.d(TAG, "mode=NONE"); 
          break; 
      case MotionEvent.ACTION_POINTER_DOWN: 
          oldDist = spacing(event); 
          //Log.d(TAG, "oldDist=" + oldDist); 
          if (oldDist > 10f) { 
              savedMatrix.set(matrix); 
              midPoint(mid, event); 
              mode = ZOOM; 
              //Log.d(TAG, "mode=ZOOM"); 
          } 
          break; 
      case MotionEvent.ACTION_UP: 
      case MotionEvent.ACTION_POINTER_UP: 
          mode = NONE; 
          //Log.e("view.getWidth", view.getWidth() + ""); 
          //Log.e("view.getHeight", view.getHeight() + ""); 

          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); 
              //Log.d(TAG, "newDist=" + newDist); 
              if (newDist > 10f) { 
                  matrix.set(savedMatrix); 
                  float scale = newDist / oldDist; 
                  matrix.postScale(scale, scale, mid.x, mid.y); 
              } 
          } 
          break; 
      } 

      view.setImageMatrix(matrix); 
      return true; // indicate event was handled 
  } 

  private void dumpEvent(MotionEvent event) { 
      String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE", 
              "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" }; 
      StringBuilder sb = new StringBuilder(); 
      int action = event.getAction(); 
      int actionCode = action & MotionEvent.ACTION_MASK; 
      sb.append("event ACTION_").append(names[actionCode]); 
      if (actionCode == MotionEvent.ACTION_POINTER_DOWN 
              || actionCode == MotionEvent.ACTION_POINTER_UP) { 
          sb.append("(pid ").append( 
                  action >> MotionEvent.ACTION_POINTER_ID_SHIFT); 
          sb.append(")"); 
      } 
      sb.append("["); 
      for (int i = 0; i < event.getPointerCount(); i++) { 
          sb.append("#").append(i); 
          sb.append("(pid ").append(event.getPointerId(i)); 
          sb.append(")=").append((int) event.getX(i)); 
          sb.append(",").append((int) event.getY(i)); 
          if (i + 1 < event.getPointerCount()) 
              sb.append(";"); 
      } 
      sb.append("]"); 
      //Log.d(TAG, sb.toString()); 
  } 

  
  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); 
  } 


}

<?xml version="1.0" encoding="UTF-8"?> 

  <LinearLayout 
  xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" 
  android:layout_height="fill_parent" 
  android:layout_width="fill_parent" 
  android:id="@+id/linearLayout1" 
  android:weightSum="1"> 
    <ImageView android:layout_width="fill_parent" 
    android:id="@+id/priviewimage" 
    android:layout_height="fill_parent" 
    android:layout_gravity="center" 
    android:scaleType="matrix" 
    > 
   </ImageView> 
  </LinearLayout> 

priviewimage.setImageBitmap(ActivityPreviewImage.click_bitmap); 
priviewimage=(ImageView)findViewById(R.id.priviewimage); 
priviewimage.setOnTouchListener(new MulitPointTouchListener());