问题说明:当SwipeRefreshLayout中放置了ViewPager控件,两者的滑动会相互冲突.具体表现为ViewPager的左右滑动不顺畅,容易被SwipeRefreshLayout拦截(即出现刷新的View).
问题原因:ViewPager本身是处理了滚动事件的冲突,它在横向滑动时会调用requestDisallowInterceptTouchEvent()方法使父控件不拦截当前的Touch事件序列.但是SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么也没有做,所以仍然会拦截当前的Touch事件序列.
问题分析:为什么SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么都不做?
首先SwipeRefreshLayout继承自ViewGroup.
在requestDisallowInterceptTouchEvent()方法什么都不做的情况下,用户可以从底部下拉刷新一次拉出LoadingView.如果方法调用ViewGroup的requestDisallowInterceptTouchEvent()方法, 可以解决ViewPager的兼容问题,但是用户在界面底部下拉至头部后,无法继续下拉,需要手指放开一次才能拉出LoadingView.目标分析:那么为了更加顺滑地滚动,想要的效果当然是一次性拉出LoadingView.既然ViewPager在左右滑动时才会调用requestDisallowInterceptTouchEvent()方法,那么SwipeRefreshLayout只应该在上下滑动时才拦截Touch事件.
具体逻辑如下:
记录是否调用了requestDisallowInterceptTouchEvent()方法,并且设置为true.在SwipeRefreshLayout中判断是否是上下滑动.如果同时满足1,2,则调用super.requestDisallowInterceptTouchEvent(true).否则调用super.requestDisallowInterceptTouchEvent(false).注意:因为ViewGroup的requestDisallowInterceptTouchEvent方法设置true后,Touch事件在dispatchTouchEvent()方法中就会被拦截,所以需要在dispatchTouchEvent()方法中判断是否为上下滑动.
实现代码(部分):
//非法按键private static final int INVALID_POINTER = -1;//dispatch方法记录第一次按下的xprivate float mInitialDisPatchDownX;//dispatch方法记录第一次按下的yprivate float mInitialDisPatchDownY;//dispatch方法记录的手指private int mActiveDispatchPointerId = INVALID_POINTER;//是否请求拦截private boolean hasRequestDisallowIntercept = false;@Overridepublic void requestDisallowInterceptTouchEvent(boolean b) { hasRequestDisallowIntercept = b; // Nope.}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mActiveDispatchPointerId = MotionEventCompat.getPointerId(ev, 0); final float initialDownX = getMotionEventX(ev, mActiveDispatchPointerId); if (initialDownX != INVALID_POINTER) { mInitialDisPatchDownX = initialDownX; } final float initialDownY = getMotionEventY(ev, mActiveDispatchPointerId); if (mInitialDisPatchDownY != INVALID_POINTER) { mInitialDisPatchDownY = initialDownY; } break; case MotionEvent.ACTION_MOVE: if (hasRequestDisallowIntercept) { //解决viewPager滑动冲突问题 final float x = getMotionEventX(ev, mActiveDispatchPointerId); final float y = getMotionEventY(ev, mActiveDispatchPointerId); if (mInitialDisPatchDownX != INVALID_POINTER && x != INVALID_POINTER && mInitialDisPatchDownY != INVALID_POINTER && y != INVALID_POINTER) { final float xDiff = Math.abs(x - mInitialDisPatchDownX); final float yDiff = Math.abs(y - mInitialDisPatchDownY); if (xDiff > mTouchSlop && xDiff * 0.7f > yDiff) { //横向滚动不需要拦截 super.requestDisallowInterceptTouchEvent(true); } else { super.requestDisallowInterceptTouchEvent(false); } } else { super.requestDisallowInterceptTouchEvent(false); } } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: if (ev.getAction() == MotionEvent.ACTION_UP || ev.getAction() == MotionEvent.ACTION_CANCEL) { hasRequestDisallowIntercept = false; } break; } return super.dispatchTouchEvent(ev);}private float getMotionEventY(MotionEvent ev, int activePointerId) { final int index = MotionEventCompat.findPointerIndex(ev, activePointerId); if (index < 0) { return -1; } return MotionEventCompat.getY(ev, index);}private float getMotionEventX(MotionEvent ev, int activePointerId) { final int index = MotionEventCompat.findPointerIndex(ev, activePointerId); if (index < 0) { return -1; } return MotionEventCompat.getX(ev, index);}
每一个成功者都有一个开始。勇于开始，才能找到成功的路。
