Recyclerview - 无法在滚动回调中调用此方法答案

【问题标题】：Recyclerview - cannot call this method in a scroll callbackRecyclerview - 无法在滚动回调中调用此方法
【发布时间】：2017-08-14 02:47:13
【问题描述】：

我在 StackOverflow 中多次看到这个问题，但我无法解决这个问题。于是伸出援手。

请注意：我已经检查了关于 SO 的其他问题，虽然我可以摆脱错误，但还有其他问题。

这是我现有的代码：

我的适配器类：

  public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

        Context context;

        private final int VIEW_TYPE_ITEM = 0;
        private final int VIEW_TYPE_LOADING = 1;
        private IOnLoadMoreListener mIOnLoadMoreListener;

        private int visibleThreshold = 3;
        private int lastVisibleItem, totalItemCount;
        private int[] lastVisibleItems = new int[mStaggeredLayoutManager.getSpanCount()];

        public RecyclerViewAdapter(Context context) {
            this.context = context;

            final StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) recyclerView.getLayoutManager();

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

                    totalItemCount = staggeredGridLayoutManager.getItemCount();
                    lastVisibleItems = staggeredGridLayoutManager.findLastVisibleItemPositions(new int[mStaggeredLayoutManager.getSpanCount()]);

                    if (staggeredGridLayoutManager.getSpanCount() == 1) {
                        lastVisibleItem = lastVisibleItems[0];
                    } else if (staggeredGridLayoutManager.getSpanCount() == 2) {
                        lastVisibleItem = Math.max(lastVisibleItems[0], lastVisibleItems[1]);
                    } else if (staggeredGridLayoutManager.getSpanCount() == 3) {
                        lastVisibleItem = Math.max(Math.max(lastVisibleItems[0], lastVisibleItems[1]), lastVisibleItems[2]);
                    }

                    if (!isRefreshing && totalItemCount <= lastVisibleItem + visibleThreshold) {

                        if (mIOnLoadMoreListener != null) {
                            mIOnLoadMoreListener.onLoadMore();
                        }

                        isRefreshing = true;
                    }
                }
            });

        }

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

            if (viewType == VIEW_TYPE_ITEM) {

                View v = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.item_recyclerview_shop_fragment, parent, false);
                return new CustomViewHolder(v);
            } else if (viewType == VIEW_TYPE_LOADING) {

                View v = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.item_recyclerview_loading_shop_fragment, parent, false);
                return new LoadingViewHolder(v);
            }

            return null;
        }

        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

            Product item = listItems.get(position);

            if (holder.getItemViewType() == VIEW_TYPE_ITEM) {

                CustomViewHolder customViewHolder = (CustomViewHolder) holder;
                Glide.with(context).load(item.getFeaturedSrc()).into(customViewHolder.imageView);

            } else if (holder.getItemViewType() == VIEW_TYPE_LOADING) {

                if (holder instanceof LoadingViewHolder) {
                    LoadingViewHolder loadingViewHolder = (LoadingViewHolder) holder;
                    loadingViewHolder.progressBar.setIndeterminate(true);
                }
            }


        }

        @Override
        public int getItemCount() {
            return listItems == null ? 0 : listItems.size();
        }

        @Override
        public int getItemViewType(int position) {

            if (listItems.get(position) == null) {
                return VIEW_TYPE_LOADING;
            } else {
                return VIEW_TYPE_ITEM;
            }
        }

        public void setOnLoadMoreListener(IOnLoadMoreListener mIOnLoadMoreListener) {
            this.mIOnLoadMoreListener = mIOnLoadMoreListener;
        }


        public class CustomViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

            ImageView imageView;
            TextView textView;

            String id;

            public CustomViewHolder(View itemView) {
                super(itemView);

                itemView.setOnClickListener(this);
                imageView = (ImageView) itemView.findViewById(R.id.imageView_thumbnail);

            }

            @Override
            public void onClick(View v) {

                int position = getAdapterPosition();

            }
        }

        public class LoadingViewHolder extends RecyclerView.ViewHolder {
            public ProgressBar progressBar;

            public LoadingViewHolder(View progressView) {
                super(progressView);
                progressBar = (ProgressBar) progressView.findViewById(R.id.progressBar);
            }
        }

    }

我之前的代码：

   mRecyclerViewAdapter.setOnLoadMoreListener(new IOnLoadMoreListener() {
        @Override
        public void onLoadMore() {

            listItems.add(null);

            mRecyclerViewAdapter.notifyItemChanged(listItems.size() - 1);
            mRecyclerViewAdapter.notifyDataSetChanged();

            isProgressVisible = true;

            getDataFromServer(false);

        }
    });

使用我的旧代码，我得到以下 IllegalStateException：

W/RecyclerView: Cannot call this method in a scroll callback. Scroll callbacks mightbe run during a measure & layout pass where you cannot change theRecyclerView data. Any method call that might change the structureof the RecyclerView or the adapter contents should be postponed tothe next frame.
java.lang.IllegalStateException: 

at android.support.v7.widget.RecyclerView.assertNotInLayoutOrScroll(RecyclerView.java:2581)
at android.support.v7.widget.RecyclerView$RecyclerViewDataObserver.onItemRangeChanged(RecyclerView.java:4943)
at android.support.v7.widget.RecyclerView$AdapterDataObservable.notifyItemRangeChanged(RecyclerView.java:11373)
at android.support.v7.widget.RecyclerView$AdapterDataObservable.notifyItemRangeChanged(RecyclerView.java:11364)
at android.support.v7.widget.RecyclerView$Adapter.notifyItemChanged(RecyclerView.java:6652)
at codsiga.com.xx.ShopFragment$1.onLoadMore(ShopFragment.java:148)
at codsiga.com.xx.ShopFragment$RecyclerViewAdapter$1.onScrolled(ShopFragment.java:229)
at android.support.v7.widget.RecyclerView.dispatchOnScrolled(RecyclerView.java:4618)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep3(RecyclerView.java:3679)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3323)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3844)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:636)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1795)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:131)
at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1391)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:870)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)

03-22 11:36:32.083 3189-3189/codsiga.com.xx W/RecyclerView:    
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:726)
at android.view.View.layout(View.java:17637)
at android.view.ViewGroup.layout(ViewGroup.java:5575)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2346)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2068)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6337)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874)
at android.view.Choreographer.doCallbacks(Choreographer.java:686)
at android.view.Choreographer.doFrame(Choreographer.java:621)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

因此，根据各种 StackOverflow 答案的建议，我将其修改如下：

修改代码查看各种答案：

mRecyclerViewAdapter.setOnLoadMoreListener(new IOnLoadMoreListener() {
            @Override
            public void onLoadMore() {

                recyclerView.post(new Runnable() {
                    @Override
                    public void run() {

                        listItems.add(null);

                        mRecyclerViewAdapter.notifyItemChanged(listItems.size() - 1);
                        mRecyclerViewAdapter.notifyDataSetChanged();

                        isProgressVisible = true;

                        getDataFromServer(false);


                    }
                });
            }
        });

现在，我没有收到错误，但 onLoadMore() 每次都被调用两次，并且 recyclerview 中的视图每次都保持刷新。我做错了什么？请看logcat输出：

D/xx: Response => {…}
D/xx: Length = 9
D/xx: Query 'SELECT * FROM products' returned 9 rows

D/xx: Response => {…}
D/xx: Length = 9
D/xx: Query 'SELECT * FROM products' returned 18 rows

【问题讨论】：

投反对票有什么理由吗？没有先尝试解决方案就没有问这个问题。非常感谢任何指导

标签： android android-recyclerview

【解决方案1】：

无法在滚动回调中调用此方法。滚动回调可能是在无法更改的测量和布局过程中运行 TheRecyclerView 数据。任何可能改变 RecyclerView 或适配器内容的结构应该是推迟到下一帧。

警告本身就是一种解释。 换句话说，您正在更新视图，而 recyclerview 正在计算布局测量值。

出了什么问题？下面的实现 -

mRecyclerViewAdapter.notifyItemChanged(listItems.size() - 1);
mRecyclerViewAdapter.notifyDataSetChanged();

您可以做的就是将此 UI 操作发布到下一个 UI 框架。你可以通过调用View.post() 方法来做到这一点。

recyclerView.post(new Runnable() {
        public void run() {
            // There is no need to use notifyDataSetChanged()
            mRecyclerViewAdapter.notifyItemInserted(allArticles.size() - 1);
        }
    });

【讨论】：

这有同样的效果，负载 more 被调用了两次。我想我会再次检查我的逻辑并回复你。谢谢
我认为问题是您试图在滚动时将项目添加到 recyclerview。
我有同样的警告信息，即不能在滚动中调用此方法。我已经应用了 Recylerview.post 方法。请提供另一种解决方案。
@axita.savani，这很奇怪，view.post { adapter.addItem() } 经常帮助我。
@axita.savani，ViewTreeObserver 可以帮忙吗？见stackoverflow.com/questions/12867760/…。您也可以通过代码示例提出问题。

【解决方案2】：

我使用以下变体更新recyclerViewAdapter：

java:

recyclerView.post(new Runnable() {
    public void run() {
        mRecyclerViewAdapter.notifyDataSetChanged();
    }
});

kotlin：

recyclerView.post {
    mRecyclerViewAdapter.notifyDataSetChanged()
}

【讨论】：