java–RecyclerView在滚动时崩溃

概述我有一些图像排列在水平网格中.我想使用键事件从左到右和从右到左移动网格.当我穿过网格时,发生了两件事>选择第二个位置的项目.例如,我在位置0并且想要选择位置1处的下一个项目,但我的网格选择位置2项目并跳过位置1项目.>在滚动时我得到空指针异常if(keyCode==KeyEvent.KEYC

我有一些图像排列在水平网格中.我想使用键事件从左到右和从右到左移动网格.当我穿过网格时,发生了两件事

>选择第二个位置的项目.例如,我在位置0并且想要选择位置1处的下一个项目,但我的网格选择位置2项目并跳过位置1项目.
>在滚动时我得到空指针异常

if(keyCode == KeyEvent.KEYCODE_DPAD_RIGHT)  {     if (mCurrentSelectedposition + 1 < getItemCount()) {    Log.e("current position1",Integer.toString(mCurrentSelectedposition));    grIDHolder = (GrIDVIEw_Holder) mRecyclerVIEw.findVIEwHolderForposition(mCurrentSelectedposition);    grIDHolder.itemVIEw.setSelected(false);    notifyItemChanged(mCurrentSelectedposition);    notifyDataSetChanged();    int lastItem = lm.findLastCompletelyVisibleItemposition();    Log.e("last item",Integer.toString(lastItem));    if ((mCurrentSelectedposition + 1) > lastItem) {        //  Log.e("Is less", "true");        recyclerVIEw.smoothScrollToposition(mCurrentSelectedposition + 1);        Log.e("current position2",Integer.toString(mCurrentSelectedposition));    } else {        grIDHolder = (GrIDVIEw_Holder) mRecyclerVIEw.findVIEwHolderForposition(mCurrentSelectedposition + 1);        grIDHolder.itemVIEw.setSelected(true);        Log.e("current position3",Integer.toString(mCurrentSelectedposition));    }    mCurrentSelectedposition += 1;    Log.e("current position4",Integer.toString(mCurrentSelectedposition));}return true;}

滚动监听器

grIDRecyclerVIEw.addOnScrollListener(new RecyclerVIEw.OnScrollListener(){        @OverrIDe        public voID onScrolled(RecyclerVIEw recyclerVIEw, int x, int y)        {            super.onScrolled(recyclerVIEw, x, y);            try {                GrIDVIEw_Holder grIDHolder;                grIDHolder= (GrIDVIEw_Holder) recyclerVIEw.findVIEwHolderForposition(adapter.mCurrentSelectedposition);                grIDHolder.itemVIEw.setSelected(true);            }catch(Exception e){               Log.e("exception",e.getMessage());           }        }

这是我的logcat

java.lang.NullPointerException: Attempt to read from fIEld 'androID.vIEw.VIEw androID.support.v7.Widget.RecyclerVIEw$VIEwHolder.itemVIEw' on a null object referenceat com.winettv.recylcervIEwwithdpad.GrIDVIEw_Recycler_Adapter.onKey(GrIDVIEw_Recycler_Adapter.java:193)at androID.vIEw.VIEw.dispatchKeyEvent(VIEw.java:9230)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1635)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.Widget.ScrollVIEw.dispatchKeyEvent(ScrollVIEw.java:379)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at androID.vIEw.VIEwGroup.dispatchKeyEvent(VIEwGroup.java:1640)at com.androID.internal.policy.PhoneWindow$DecorVIEw.superdispatchKeyEvent(PhoneWindow.java:2395)at com.androID.internal.policy.PhoneWindow.superdispatchKeyEvent(PhoneWindow.java:1727)at androID.app.Activity.dispatchKeyEvent(Activity.java:2725)at androID.support.v7.app.AppCompatActivity.dispatchKeyEvent(AppCompatActivity.java:543)at androID.support.v7.vIEw.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:53)at androID.support.v7.app.AppCompatDelegateImplBase$AppCompatwindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:315)

解决方法:

当我在滚动期间开发带有自定义翻译的库时,我遇到了同样的问题.只有在快速滚动时,当我尝试从List访问VIEw元素时,这是null,这里是NPE.

所以有一个非常简单的解决方案只是跳过元素,这是空的,并继续新的元素.就我而言,它是这样的：

// Other init....for (int i = 0; i < MainListVIEw.getChildCount; i++) {   if (MainListVIEw.getChildAt(i) == null)      continue;   // Continue base behavior}

发生这种情况,基于ScrollVIEw(它是RecycleVIEw,ListVIEw等的父级)当我们尝试访问正在重绘的VIEw时.无论如何只需简单的Null检查就可以解决您的问题.

更新1：

同样基于缓存查看RecyclerVIEw的布局,您还需要另一个选项.见下文.

grIDRecyclerVIEw.addOnScrollListener(new RecyclerVIEw.OnScrollListener(){        @OverrIDe        public voID onScrolled(RecyclerVIEw recyclerVIEw, int x, int y)        {            super.onScrolled(recyclerVIEw, x, y);            GrIDVIEw_Holder grIDHolder;            grIDHolder= (GrIDVIEw_Holder) recyclerVIEw.findVIEwHolderForposition(adapter.mCurrentSelectedposition);            if (grIDHolder != null && grIDHolder.itemVIEw != null) {                   grIDHolder.itemVIEw.setSelected(true);            }        }}

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