LinearLayoutManager.findLastVisibleItemPosition()返回假位置

Question

我使用下面的方法来实现延迟加载，用于分页在RecyclerView中

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            totalItemCount = linearLayoutManager.getItemCount();
            lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition(); // starts with 0

            if (!mIsLoading && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                if (mOnLoadMoreListener != null) {
                    mOnLoadMoreListener.onLoadMore();
                }

                mIsLoading = true;
            }

        }
    });

它在API级别> 22上工作得很好。但是，在API 22和更低版本上，onScrolled()本身会被多次调用，直到加载所有页面为止。这最终导致应用程序崩溃，并出现以下错误：

    java.lang.IndexOutOfBoundsException: Inconsistency detected. Invalid view holder adapter positionViewHolder{52d05fac position=6 id=-1, oldPos=5, pLpos:5 scrap [attachedScrap] tmpDetached no parent} android.support.v7.widget.RecyclerView{52820a2c VFED.... .F....ID 0,213-656,3401 #7f0a0122 app:id/
 at android.support.v7.widget.RecyclerView$Recycler.validateViewHolderForOffsetPosition(RecyclerView.java:5610)
        at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5792)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5752)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5748)
        at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2232)
        at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1559)
        at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1519)
        at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:614)
        at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3763)
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:3219)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:15848)
        at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1217)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.widget.ScrollView.onMeasure(ScrollView.java:321)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:739)
        at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:91)
        at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1361)
        at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:809)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:141)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:15848)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189)
        at andro

另一方面，当我添加dy>0条件时，onScrolled()只被调用一次：

if (!mIsLoading && totalItemCount <= (lastVisibleItem + visibleThreshold) && dy>0) {
            .
            .
            .
}

如果有人遇到这样的问题或有了解决办法，我会非常感激他们能分享他们的意见。谢谢。

Answer 1

找到了答案：

我在RecyclerView布局中的ScrollView中使用了ScrollView。我认为ScrollView滚动操作侦听器对API<=22中的回收视图有先见之明。不管怎样，我发现this的回答很有帮助。

注：，如果你给RecyclerView一个固定的高度，它也会在ScrollView里面工作。