Android实现对imageview的拖动以及缩放

package org.wch.gesture;import android.graphics.Matrix;  import android.graphics.PointF;  import android.util.FloatMath;  import android.util.Log;import android.view.MotionEvent;  import android.view.View;  import android.view.View.OnTouchListener;  import android.widget.ImageView;  import android.widget.ImageView.ScaleType;  public class MulitPointTouchListener implements OnTouchListener {  Matrix matrix = new Matrix();  Matrix savedMatrix = new Matrix();  public ImageView image;  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;  public MulitPointTouchListener(ImageView image) {  super();  this.image = image;  }  @Override  public boolean onTouch(View v, MotionEvent event) {  this.image.setScaleType(ScaleType.MATRIX);  ImageView view = (ImageView) v;  //dumpEvent(event);  switch (event.getAction() & MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN:  Log.w("FLAG", "ACTION_DOWN");matrix.set(view.getImageMatrix());  savedMatrix.set(matrix);  start.set(event.getX(), event.getY());  mode = DRAG;  break;  case MotionEvent.ACTION_POINTER_DOWN:  Log.w("FLAG", "ACTION_POINTER_DOWN");oldDist = spacing(event);  if (oldDist > 10f) {  savedMatrix.set(matrix);  midPoint(mid, event);  mode = ZOOM;  }  break;  case MotionEvent.ACTION_UP:  Log.w("FLAG", "ACTION_UP");case MotionEvent.ACTION_POINTER_UP:  Log.w("FLAG", "ACTION_POINTER_UP");mode = NONE;  break;  case MotionEvent.ACTION_MOVE:  Log.w("FLAG", "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);  }  }
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