【Android】多点触控（判断触摸点是否在view上）
【关键词】
Android 多点触控
【问题】
- 如何获取单个触摸点的位置，多个触摸点的位置又如何获取呢？
- 如何根据触摸点的位置，确定触摸点是否在 view 上？
【效果图】
【分析】
- 通过
MotionEvent可以获取到触摸点个数； - 通过
MotionEvent.getX(int pointerIndex)方法，可以获取到指定触摸点的X值；对于Y坐标同理；
【解决方案】
- 参考源代码
【代码】
// -------------------- action:multi-touch time:2016.04.15 by:Lou// 重写 Activity 的 onTouchEvent方法；@Overridepublic boolean onTouchEvent(MotionEvent event) {whenTouchMove(event);if (event.getAction() == MotionEvent.ACTION_UP) {whenTouchUp();}return true;}private void whenTouchMove(MotionEvent event) {Point[] points = getCurrentPoints(event);//根据四个触摸点对四个view进行各自的处理；doResultWithPoints(mIvIndicatorTopLeft, points);doResultWithPoints(mIvIndicatorTopRight, points);doResultWithPoints(mIvIndicatorBottomLeft, points);doResultWithPoints(mIvIndicatorBottomRight, points);}private static final int MAX_TOUCH_POINT = 4; // 最多监听4个触点；// 获取当前所有触摸点的位置；public static Point[] getCurrentPoints(MotionEvent event){int pointerCount = event.getPointerCount();if (pointerCount > MAX_TOUCH_POINT) {pointerCount = MAX_TOUCH_POINT;}Point[] points = new Point[pointerCount];for (int i = 0; i < pointerCount; i++) {points[i] = new Point((int) event.getX(i), (int) event.getY(i));}return points;}// 判断一组触摸点是否在 view上；public static boolean isTouchPointInView(View view, Point[] points) {if (view == null && points == null) {throw new NullPointerException();}int len = points.length;boolean result = false;for (int i = 0; i < len; i++) {if (isTouchPointInView(view, points[i])) {result = true;break;}}return result;}// 判断一个具体的触摸点是否在 view 上；public static boolean isTouchPointInView(View view, Point point) {if (view == null && point == null) {throw new NullPointerException();}int[] location = new int[2];view.getLocationOnScreen(location);int left = location[0];int top = location[1];int right = left + view.getMeasuredWidth();int bottom = top + view.getMeasuredHeight();if (point.x >= left && point.x <= right && point.y >= top && point.y <= bottom) {return true;}return false;}// 根据触摸点是否在 view 上进行处理；private void doResultWithPoints(ImageView iv, Point[] points) {boolean result = isTouchPointInView(iv, points);if (result) { // 在范围内：// TODO} else { // 不在范围内：// TODO}}// 当所有触摸点都松开的时候执行；private void whenTouchUp() {// TODO}// ~~~~~~~~~~~~~~~~~~~~
【参考资料】
- Android L中水波纹点击效果的实现