Removing an item causes NullPointerException

[burcsade]

When an item is removed from the backing dataset and adapter is notified via notifyItemRemoved method, demo app crashes with NullPointerException.

• Add method to DataAdapter and call it within MainActivity

  fun removeData() {
      // remove last item for test purposes
      val orgListSize = list.size
      this.list = this.list.subList(0, orgListSize - 1).toList()
      notifyItemRemoved(orgListSize - 1)
  }

• App crashes with the following exception log

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.jackandphantom.carousellayout, PID: 28559
    java.lang.NullPointerException
        at com.jackandphantom.carouselrecyclerview.CarouselLayoutManager.getChildActualPos(CarouselLayoutManager.kt:468)
        at com.jackandphantom.carouselrecyclerview.CarouselRecyclerview.getChildDrawingOrder(CarouselRecyclerview.kt:106)
        at android.view.ViewGroup.getAndVerifyPreorderedIndex(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4351)
        at android.view.View.draw(View.java:22670)
        at androidx.recyclerview.widget.RecyclerView.draw(RecyclerView.java:4429)
        at android.view.View.updateDisplayListIfDirty(View.java:21491)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.updateDisplayListIfDirty(View.java:21482)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.updateDisplayListIfDirty(View.java:21482)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.updateDisplayListIfDirty(View.java:21482)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.updateDisplayListIfDirty(View.java:21482)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.updateDisplayListIfDirty(View.java:21482)
        at android.view.View.draw(View.java:22377)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4595)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4354)
        at android.view.View.draw(View.java:22670)
        at com.android.internal.policy.DecorView.draw(DecorView.java:826)
        at android.view.View.updateDisplayListIfDirty(View.java:21491)
        at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:559)
        at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:565)
        at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:642)
        at android.view.ViewRootImpl.draw(ViewRootImpl.java:4372)
        at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:4077)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:3335)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:2135)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8636)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1035)
        at android.view.Choreographer.doCallbacks(Choreographer.java:858)
        at android.view.Choreographer.doFrame(Choreographer.java:789)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1020)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:236)
        at android.app.ActivityThread.main(ActivityThread.java:8045)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:620)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1011)

[sparrow007]

Hi @burcsade thanks for very great explanation on the adapter update exception, i will fix the issue ASAP