ConsecutiveViewPager2 裡放 StaggeredGridLayoutManager RecyclerView，切換 ConsecutiveViewPager2 會閃退

[klps5603]

您好，我在 ConsecutiveViewPager2 Fragment 中放 StaggeredGridLayoutManager RecyclerView，切換 ConsecutiveViewPager2 時，會出現以下錯誤訊息：

java.lang.NullPointerException: Attempt to read from field 'java.util.ArrayList androidx.recyclerview.widget.StaggeredGridLayoutManager$Span.mViews' on a null object reference in method 'void androidx.recyclerview.widget.StaggeredGridLayoutManager.recycleFromEnd(androidx.recyclerview.widget.RecyclerView$Recycler, int)'
at androidx.recyclerview.widget.StaggeredGridLayoutManager.recycleFromEnd(StaggeredGridLayoutManager.java:1928)
at androidx.recyclerview.widget.StaggeredGridLayoutManager.recycle(StaggeredGridLayoutManager.java:1762)
at androidx.recyclerview.widget.StaggeredGridLayoutManager.fill(StaggeredGridLayoutManager.java:1681)
at androidx.recyclerview.widget.StaggeredGridLayoutManager.scrollBy(StaggeredGridLayoutManager.java:2154)
at androidx.recyclerview.widget.StaggeredGridLayoutManager.scrollVerticallyBy(StaggeredGridLayoutManager.java:2013)
at androidx.recyclerview.widget.RecyclerView.scrollStep(RecyclerView.java:1972)
at androidx.recyclerview.widget.RecyclerView.scrollByInternal(RecyclerView.java:2071)
at androidx.recyclerview.widget.RecyclerView.scrollBy(RecyclerView.java:1880)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollChild(ConsecutiveScrollerLayout.java:1301)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollDown(ConsecutiveScrollerLayout.java:1219)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.dispatchScroll(ConsecutiveScrollerLayout.java:1101)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollTo(ConsecutiveScrollerLayout.java:1250)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollBy(ConsecutiveScrollerLayout.java:1244)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollChild(ConsecutiveScrollerLayout.java:1301)
at com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout.scrollChildContentToTop(ConsecutiveScrollerLayout.java:1455)
at com.donkingliang.consecutivescroller.ConsecutiveViewPager2.scrollChildContent(ConsecutiveViewPager2.java:176)
at com.donkingliang.consecutivescroller.ConsecutiveViewPager2.access$000(ConsecutiveViewPager2.java:29)
at com.donkingliang.consecutivescroller.ConsecutiveViewPager2$AttachListener.onViewAttachedToWindow(ConsecutiveViewPager2.java:283)
at android.view.View.dispatchAttachedToWindow(View.java:23238)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3698)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3705)
at android.view.ViewGroup.addViewInner(ViewGroup.java:5552)
at android.view.ViewGroup.addView(ViewGroup.java:5328)
at android.view.ViewGroup.addView(ViewGroup.java:5268)
at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:889)
at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8902)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8860)
at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1647)
at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
at androidx.recyclerview.widget.LinearLayoutManager.scrollBy(LinearLayoutManager.java:1395)
at androidx.recyclerview.widget.LinearLayoutManager.scrollHorizontallyBy(LinearLayoutManager.java:1124)
at androidx.recyclerview.widget.RecyclerView.scrollStep(RecyclerView.java:1969)
at androidx.recyclerview.widget.RecyclerView$SmoothScroller.onAnimation(RecyclerView.java:12316)
at androidx.recyclerview.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:5564)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1689)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1698)
at android.view.Choreographer.doCallbacks(Choreographer.java:1153)
at android.view.Choreographer.doFrame(Choreographer.java:1069)
14:34:34.591 E at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1646) (Ask Gemini)
at android.os.Handler.handleCallback(Handler.java:958)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:230)
at android.os.Looper.loop(Looper.java:319)

當我先到Ａ tab Fragment recyclerView 是有多筆內容的，並往下捲動，之後切換到 B tab Fragment recyclerView 沒有資料，向上捲動最外層的 ConsecutiveScrollerLayout，最後切換回 Ａ tab Fragment recyclerView，會出現這個問題

覺得是回收與重繪 StaggeredGridLayoutManager ，佈局出現問題

請問大大有沒有類似的經驗，謝謝

[klps5603]

   <com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout
           android:layout_width="match_parent"
           android:layout_height="match_parent">

         <com.donkingliang.consecutivescroller.ConsecutiveViewPager2 
                 android:layout_width="match_parent"
                 android:layout_height="match_parent" />

  </com.donkingliang.consecutivescroller.ConsecutiveScrollerLayout>

更正，ConsecutiveViewPager2 額外包個 ConsecutiveScrollerLayout ，可能有些多餘但可以解決問題
但往下捲動 A Tab Fragment，切換到 B Tab Fragment ，向上捲動最外層 ConsecutiveScrollerLayout （不吸頂狀態）， 回到 A Tab Fragment ，捲動 RecyclerView 時，他會自行捲動到 RecyclerView 頂部，不會記錄上次滑動的位置

[donkingliang]

如果你想保持RecyclerView 原本的滑动位置，可以重新ConsecutiveViewPager2 的getScrolledViews方法，返回null

[klps5603]

class ConsecutiveViewPager2(context: Context, attrs: AttributeSet? = null) :
        ConsecutiveViewPager2(context, attrs) {
               override fun getScrolledViews(): MutableList<View> {
                    return mutableListOf()
                }

  }

getScrolledViews 應是回一個空 list ，但沒有效果

[klps5603]

懂了，我改重寫成 return null ，再試試看，謝謝

[klps5603]

還是有機會出現 RecyclerView 自動滑到頂的問題，當不吸頂的狀態下