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);		}	}