android判定滑动方向

	private static final float MIN_OFFSET = 8;
	private float startX,startY,offsetX,offsetY;
	private String action;
	
		@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub
//		return gestureDetector.onTouchEvent(event);

		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			startX = event.getX();
			startY = event.getY();
			break;
		case MotionEvent.ACTION_UP:
			offsetX = event.getX()-startX;
			offsetY = event.getY()-startY;
			if(Math.abs(offsetX) < MIN_OFFSET  && Math.abs(offsetY)< MIN_OFFSET){
				return false;
			}
			if (Math.abs(offsetX)>Math.abs(offsetY)) {
				if (offsetX<-MIN_OFFSET) {
					action = "left";
				}else if (offsetX>MIN_OFFSET) {
					action = "right";
				}
			}else{
				if (offsetY<-MIN_OFFSET) {
					action = "up";
				}else if (offsetY>MIN_OFFSET) {
					action = "down";
				}
			}
			Toast.makeText(this, action, Toast.LENGTH_SHORT).show();
			break;
		}
		return true;
	}