問題說明:
當(dāng)SwipeRefreshLayout中放置了ViewPager控件,兩者的滑動(dòng)會(huì)相互沖突.具體表現(xiàn)為ViewPager的左右滑動(dòng)不順暢,容易被SwipeRefreshLayout攔截(即出現(xiàn)刷新的View).
問題原因:
ViewPager本身是處理了滾動(dòng)事件的沖突,它在橫向滑動(dòng)時(shí)會(huì)調(diào)用requestDisallowInterceptTouchEvent()方法使父控件不攔截當(dāng)前的Touch事件序列.但是SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么也沒有做,所以仍然會(huì)攔截當(dāng)前的Touch事件序列.
問題分析:
為什么SwipeRefreshLayout的requestDisallowInterceptTouchEvent()方法什么都不做?
首先SwipeRefreshLayout繼承自ViewGroup.
在requestDisallowInterceptTouchEvent()方法什么都不做的情況下,用戶可以從底部下拉刷新一次拉出LoadingView.
如果方法調(diào)用ViewGroup的requestDisallowInterceptTouchEvent()方法, 可以解決ViewPager的兼容問題,但是用戶在界面底部下拉至頭部后,無法繼續(xù)下拉,需要手指放開一次才能拉出LoadingView.
目標(biāo)分析:
那么為了更加順滑地滾動(dòng),想要的效果當(dāng)然是一次性拉出LoadingView.既然ViewPager在左右滑動(dòng)時(shí)才會(huì)調(diào)用requestDisallowInterceptTouchEvent()方法,那么SwipeRefreshLayout只應(yīng)該在上下滑動(dòng)時(shí)才攔截Touch事件.
具體邏輯如下:
記錄是否調(diào)用了requestDisallowInterceptTouchEvent()方法,并且設(shè)置為true.
在SwipeRefreshLayout中判斷是否是上下滑動(dòng).
如果同時(shí)滿足1,2,則調(diào)用super.requestDisallowInterceptTouchEvent(true).
否則調(diào)用super.requestDisallowInterceptTouchEvent(false).
注意:因?yàn)閂iewGroup的requestDisallowInterceptTouchEvent方法設(shè)置true后,Touch事件在dispatchTouchEvent()方法中就會(huì)被攔截,所以需要在dispatchTouchEvent()方法中判斷是否為上下滑動(dòng).
實(shí)現(xiàn)代碼(部分):
//非法按鍵private static final int INVALID_POINTER = -1;//dispatch方法記錄第一次按下的xprivate float mInitialDisPatchDownX;//dispatch方法記錄第一次按下的yprivate float mInitialDisPatchDownY;//dispatch方法記錄的手指private int mActiveDispatchPointerId = INVALID_POINTER;//是否請(qǐng)求攔截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) { //解決viewPager滑動(dòng)沖突問題 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) { //橫向滾動(dòng)不需要攔截 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);}新聞熱點(diǎn)
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