Android 两点触控，获取两点间的位移变化

View main = (View) findViewById(R.id.linearLayout);
  

  main.setOnTouchListener(new OnTouchListener() {

   int mode = -1;
   int DRAG = 1;
   int NONE = 0;
   int ZOOM = 2;
   float oldDist;

   public boolean onTouch(View v, MotionEvent event) {
    // TODO Auto-generated method stub

    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
     mode = DRAG;
     break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
     mode = NONE;
     break;
    case MotionEvent.ACTION_POINTER_DOWN:
     oldDist = spacing(event);
     textView.setText("ACTION_POINTER_DOWN："+oldDist+"");
     if (oldDist > 10f) {
      mode = ZOOM;
     }
     break;
    case MotionEvent.ACTION_MOVE:
     if (mode == ZOOM) {
      // 正在移动的点距初始点的距离
      float newDist = spacing(event);
      textView.setText("ACTION_MOVE:"+newDist+"");
     }
     break;
    }

    return true;

   }
  });

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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);
 }

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