Android手势缩放图片以及图片黏贴在手指随手势移动，,一个Android手势缩

Android手势缩放图片以及图片黏贴在手指随手势移动，,一个Android手势缩

一个Android手势缩放图片的工具类；同时，此类还实现另外一个功能：当手指按在触屏上移动时候，图片“黏贴”在手指上随手指移动而整体移动。

具体使用方法可以是这样：先new一个此类的实例，然后在ImageView的方法setOnTouchListener(new ImageViewOnMultiTouchListener());

例如：

    ImageViewOnMultiTouchListener listener=new ImageViewOnMultiTouchListener();              ImageView mImageView=(ImageView)findViewById(R.id.imageView);              mImageView.setOnTouchListener(listener);  

ImageViewOnMultiTouchListener.java全部源代码：

    public class ImageViewOnMultiTouchListener implements View.OnTouchListener {              private final int NONE = 0;              private final int MOVE = 1;              private final int ZOOM = 2;              private final int DRAG = 3;              private int mode = NONE;              private Matrix matrix = new Matrix();              private Matrix savedMatrix = new Matrix();              private PointF start = new PointF();              private PointF mid = new PointF();              private float oldDistance = 0;              @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:                      oldDistance = spacing(event);                      if (oldDistance > 5f) {                          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 > 5f) {                              matrix.set(savedMatrix);                              float scale = newDist / oldDistance;                              matrix.postScale(scale, scale, mid.x, mid.y);                          }                      }                      break;                  }                  view.setImageMatrix(matrix);                  view.setScaleType(ImageView.ScaleType.MATRIX);                  view.setPadding(3, 5, 3, 5);                  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);              }          }