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在SwipeRefreshLayout的内部包一个ViewPager,这样左右滑动ViewPager的时候,顶部老是会弹出刷新按钮,滑动很不灵敏。
了解事件分发机制和事件拦截机制的都知道解决滑动冲突无非两种方法:外部拦截法和内部拦截法,现在我们运用这两种方法,解决下这个问题。
注意:如果对事件分发机制和事件拦截机制不了解的可以看我的上两篇文章《Android 源码分析事件分发机制、事件消费、事件拦截》、《一篇文章读懂android事件消费、事件分发、事件拦截》
外部拦截法
@Override public boolean onInterceptTouchEvent(MotionEvent event) { // 外部拦截法 int x = (int) event.getX(); int y = (int) event.getY(); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: { mLastX = (int) event.getX(); mLastY = (int) event.getY(); break; } case MotionEvent.ACTION_MOVE: { int deltaX = x - mLastX; int deltaY = y - mLastY; if (Math.abs(deltaX) > Math.abs(deltaY)) { return false; } break; } case MotionEvent.ACTION_UP: { break; } default: break; } return super.onInterceptTouchEvent(event); } }
外部拦截法,顾名思义,就是在外部父view里拦截,我们直接重写SwipeRefreshLayout的onInterceptTouchEvent方法,在ACTION_MOVE的时候,判断如果是水平滑动的话,不拦截事件,把事件交由子View也就是ViewPager处理就ok了。这个方法很简单,想必大家都可以想到。我们这篇文章重点是接下来的内部拦截法,通过内部拦截法教会大家真正学会去处理任何滑动冲突。
内部拦截法
@Override public boolean dispatchTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: Log.e("内部View-CustomVPInner", "dispatchTouchEvent: Down"); startX = ev.getX(); startY = ev.getY(); getParent().requestDisallowInterceptTouchEvent(true); break; case MotionEvent.ACTION_MOVE: Log.e("内部View-CustomVPInner", "dispatchTouchEvent: Move"); x = ev.getX(); y = ev.getY(); deltaX = Math.abs(x - startX); deltaY = Math.abs(y - startY); if (deltaX getParent().requestDisallowInterceptTouchEvent(false); } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: break; } boolean a = super.dispatchTouchEvent(ev); Log.e("内部View-CustomVPInner", "dispatchTouchEvent: a = "+a); return a; }
我们直接重写ViewPager的dispatchTouchEvent,在Down事件的时候,请求SwipeRefreshLayout不要拦截,只有在ACTION_MOVE事件的时候,并且判断是垂直滑动的话,才请求SwipeRefreshLayout拦截。当然,还要记得重写父view也就是SwipeRefreshLayout的onInterceptTouchEvent,并且在Down的时候返回false,因为在Down的时候,是一定会去走onInterceptTouchEvent(ev);方法的。
if (actionMasked == MotionEvent.ACTION_DOWN) { // Throw away all previous state when starting a new touch gesture. // The framework may have dropped the up or cancel event for the previous gesture // due to an app switch, ANR, or some other state change. cancelAndClearTouchTargets(ev); resetTouchState(); } // Check for interception. final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) { final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { intercepted = onInterceptTouchEvent(ev); ev.setAction(action); // restore action in case it was changed } else { intercepted = false; }
因为在源码里是down事件的时候会执行resetTouchState();重置mGroupFlags标志,导致一定会执行 intercepted = onInterceptTouchEvent(ev);这条语句,所以,在内部拦截法的时候,记得在外部父view里重写onInterceptTouchEvent,并且在Down的时候返回false。
@Override public boolean onInterceptTouchEvent(MotionEvent ev) { Log.e("外部view-CustomSRL2", "onInterceptTouchEvent: "+ev.getAction()); if (ev.getAction() == MotionEvent.ACTION_DOWN) { super.onInterceptTouchEvent(ev); return false; } return true; }
现在我们运行代码,却发现还是连ViewPager都滑不动了。小伙伴们有没有觉得很奇怪呢,在很多情况下,这种方法是可以解决滑动冲突的。为什么在SwipeRefreshLayout里却不行呢?现在我们有两个思路:1.子view也就是ViewPager的dispatchTouchEvent里返回了false。2.父view还是拦截了事件,也就是getParent().requestDisallowInterceptTouchEvent(true);的方法失效了。
所以我们在SwipeRefreshLayout和ViewPager的dispatchTouchEvent里打印下日志看看
@Override public boolean onInterceptTouchEvent(MotionEvent ev) { Log.e("外部view-CustomSRL2", "onInterceptTouchEvent: "+ev.getAction()); if (ev.getAction() == MotionEvent.ACTION_DOWN) { super.onInterceptTouchEvent(ev); return false; } return true; } @Override public boolean dispatchTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: Log.e("内部View-CustomVPInner", "dispatchTouchEvent: Down"); startX = ev.getX(); startY = ev.getY(); getParent().requestDisallowInterceptTouchEvent(true); break; case MotionEvent.ACTION_MOVE: Log.e("内部View-CustomVPInner", "dispatchTouchEvent: Move"); x = ev.getX(); y = ev.getY(); deltaX = Math.abs(x - startX); deltaY = Math.abs(y - startY); if (deltaX getParent().requestDisallowInterceptTouchEvent(false); } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: break; } boolean a = super.dispatchTouchEvent(ev); Log.e("内部View-CustomVPInner", "dispatchTouchEvent: a = "+a); return a; }
2020-04-14 19:53:38.105 31242-31242/com.enjoy.srl_vp E/外部view-CustomSRL2: onInterceptTouchEvent: 0 2020-04-14 19:53:38.106 31242-31242/com.enjoy.srl_vp E/内部View-CustomVPInner: dispatchTouchEvent: Down 2020-04-14 19:53:38.107 31242-31242/com.enjoy.srl_vp E/内部View-CustomVPInner: dispatchTouchEvent: a = true 2020-04-14 19:53:38.227 31242-31242/com.enjoy.srl_vp E/外部view-CustomSRL2: onInterceptTouchEvent: 2 2020-04-14 19:53:38.227 31242-31242/com.enjoy.srl_vp E/内部View-CustomVPInner: dispatchTouchEvent: a = true
我们左滑,发现子view也就是ViewPager的dispatchTouchEvent里是返回true的,也就是接收到了事件,但是并没有走到ACTION_MOVE事件,外部SwipeRefreshLayout的onInterceptTouchEvent方法里打印出了两次,综上日志,我们分析,确实是getParent().requestDisallowInterceptTouchEvent(true);方法失效了,父view还是拦截了事件,所以我们进入requestDisallowInterceptTouchEvent方法看看,因为我们是在重写SwipeRefreshLayout所以这里的getParent就是SwipeRefreshLayout,
public void requestDisallowInterceptTouchEvent(boolean b) { if ((VERSION.SDK_INT >= 21 || !(this.mTarget instanceof AbsListView)) && (this.mTarget == null || ViewCompat.isNestedScrollingEnabled(this.mTarget))) { super.requestDisallowInterceptTouchEvent(b); } }
发现SwipeRefreshLayout里确实重写了requestDisallowInterceptTouchEvent方法,并且加了判断,requestDisallowInterceptTouchEvent方法失效,也就是没有调用到super.requestDisallowInterceptTouchEvent(b);SwipeRefreshLayout继承自ViewGroup,也就是没有调用到ViewGroup的requestDisallowInterceptTouchEvent,所以应该是前面的if判断没通过,我们运行的虚拟机是大于21的,这个VERSION.SDK_INT >= 21是满足的,因为SwipeRefreshLayout里包含了一个ViewPager ,所以SwipeRefreshLayout里有子view,也就是this.mTarget是不等于null的,
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { // Child wants to receive touch within its bounds. mLastTouchDownTime = ev.getDownTime(); if (preorderedList != null) { // childIndex points into presorted list, find original index for (int j = 0; j if (children[childIndex] == mChildren[j]) { mLastTouchDownIndex = j; break; } } } else { mLastTouchDownIndex = childIndex; } mLastTouchDownX = ev.getX(); mLastTouchDownY = ev.getY(); newTouchTarget = addTouchTarget(child, idBitsToAssign); alreadyDispatchedToNewTouchTarget = true; break; }
根据之前我们的日志,viewpager是响应了事件返回true的所以进入if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {这个判断,里面的这句 newTouchTarget = addTouchTarget(child, idBitsToAssign);就是给mTarget赋值的,所以mTarget是不为null的,所以现在我们只有看看能不能改变ViewCompat.isNestedScrollingEnabled(this.mTarget)的值,让他返回true,这样就会走super.requestDisallowInterceptTouchEvent(b)了(现在ViewCompat.isNestedScrollingEnabled(this.mTarget)是返回false的),所以我们进入ViewCompat.isNestedScrollingEnabled(this.mTarget)这个方法看看
public static void setNestedScrollingEnabled(@NonNull View view, boolean enabled) { if (VERSION.SDK_INT >= 21) { view.setNestedScrollingEnabled(enabled); } else if (view instanceof NestedScrollingChild) { ((NestedScrollingChild)view).setNestedScrollingEnabled(enabled); } }
我们发现是一个static方法,所以我们是可以通过ViewCompat类直接调用到的,所以我们在getParent().requestDisallowInterceptTouchEvent(true);前面调用 ViewCompat.setNestedScrollingEnabled(this,true);跑一下程序看看,结果我们发现是可以的,所以内部拦截法我们要在ViewPager的dispatchTouchEvent方法里这样写
@Override public boolean dispatchTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: Log.e("wdy", "dispatchTouchEvent: Down"); startX = ev.getX(); startY = ev.getY(); ViewCompat.setNestedScrollingEnabled(this,true); getParent().requestDisallowInterceptTouchEvent(true); break; case MotionEvent.ACTION_MOVE: Log.e("wdy", "dispatchTouchEvent: Move"); x = ev.getX(); y = ev.getY(); deltaX = Math.abs(x - startX); deltaY = Math.abs(y - startY); if (deltaX getParent().requestDisallowInterceptTouchEvent(false); } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: break; } boolean a = super.dispatchTouchEvent(ev); Log.e("wdy", "dispatchTouchEvent: a = "+a); return a; }
现在我们就实现了外部拦截和内部拦截两种方法解决了SwipeRefreshLayout和ViewPager滑动冲突了。
最后介绍一种方法:就是直接通过反射的方式直接更改ViewGroup里的requestDisallowInterceptTouchEvent方法里的mGroupFlags值,
@Override public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) { // We're already in this state, assume our ancestors are too return; } if (disallowIntercept) { mGroupFlags |= FLAG_DISALLOW_INTERCEPT; } else { mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT; } // Pass it up to our parent if (mParent != null) { mParent.requestDisallowInterceptTouchEvent(disallowIntercept); } }
看过viewgroup的源码的肯定都知道requestDisallowInterceptTouchEvent其实实际上就是通过改变mGroupFlags标志位来决定是否拦截事件的。所以我们可以重写requestDisallowInterceptTouchEvent,并且通过反射去改变mGroupFlags的值,使在viewgroup事件分发拦截的时候,mGroupFlags标记位满足我们的条件,反射应该属于基础知识了,我也不多说,直接给出代码,主要是位操作
@Override public void requestDisallowInterceptTouchEvent(boolean b) { Class clazz = ViewGroup.class; // FLAG_DISALLOW_INTERCEPT = 0x80000; // 1000 0000 0000 0000 0000 0x80000 //10 1100 0100 0000 0101 0011 2900051 //10 0010 0100 0100 0101 0011 2245715 try { Field mGroupFlagsField = clazz.getDeclaredField("mGroupFlags"); mGroupFlagsField.setAccessible(true); int c = (int) mGroupFlagsField.get(this); Log.e("wdy", "dispatchTouchEvent: c " + c); if (b) { //2900051&FLAG_DISALLOW_INTERCEPT =true mGroupFlagsField.set(this, 2900051); } else { //2245715&FLAG_DISALLOW_INTERCEPT =fasle mGroupFlagsField.set(this, 2245715); } } catch (Exception e) { e.printStackTrace(); } // super.requestDisallowInterceptTouchEvent(b); } final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { intercepted = onInterceptTouchEvent(ev); ev.setAction(action); // restore action in case it was changed } else { intercepted = false; }
到此,我们一共给出了三种解决SwipeRefreshLayout和ViewPager滑动冲突的方法,当然最方便的肯定是外部拦截法,我们在这里讲另外两种方法,其实就是给大家提供另外两种思路,并且带大家一步步去解决了滑动冲突的问题,相信大家认真看这篇文章肯定收获满满,以后再遇到滑动冲突,肯定毫无畏惧了,说白了就是内部拦截和外部拦截两种方法。
作者:_小三爷
链接:https://www.jianshu.com/p/2579c5b5e7bd著作权归作者所有推荐阅读
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