Xamarin RecyclerView仅三星S8报布局计算/滚动时调用方法错误求助

Hey there, let's break down why this issue only pops up on your Samsung S8 and how to fix it:

Why the Samsung S8 is the only device throwing this error #

Your hunch about the screen ratio is exactly right! The 21.5:9 aspect ratio of the S8 shows more RecyclerView items at once compared to the 16:9 S6/S4. This shifts the timing of when your load-more trigger fires—on the S8, the RecyclerView might still be in the middle of computing its layout or handling scroll-related item recycling when you try to update the adapter. RecyclerView strictly forbids calling notify methods during these operations, hence the error.

Step-by-step fixes #

Let's adjust your code to work with RecyclerView's lifecycle instead of against it:

1. Use RecyclerView.Post() to delay the adapter update
   Wrap your notify call in mRecyclerView.Post() to ensure it runs after the current layout/scroll operation finishes. Also, swap NotifyItemRangeChanged for NotifyItemRangeInserted—you're adding new items, not modifying existing ones, which is more efficient and avoids unnecessary layout conflicts:

var onScrollListener = new XamarinRecyclerViewOnScrollListener(mLayoutManager);
onScrollListener.LoadMoreEvent += (object sender, EventArgs e) => { 
    int oldCount = loadPhotos.pictures.Count;
    loadPhotos.LoadMoreItems(Constants.LOADNEXTITEMSTHRESHHOLD);
    // Post the update to run after RecyclerView finishes its current work
    mRecyclerView.Post(() => {
        int newItemsCount = loadPhotos.pictures.Count - oldCount;
        mAdapter.NotifyItemRangeInserted(oldCount, newItemsCount);
    });
};

2. Add guard clauses to skip updates when RecyclerView is busy
   Check if the RecyclerView is in the middle of layout or scroll operations before running your load-more logic. If it is, delay and retry the operation:

onScrollListener.LoadMoreEvent += (object sender, EventArgs e) => { 
    // Exit early if RecyclerView is busy with layout or scrolling
    if (mRecyclerView.IsComputingLayout || mRecyclerView.ScrollState != RecyclerView.ScrollStateIdle) {
        mRecyclerView.PostDelayed(() => {
            // Re-run the load-more logic after a short delay
            int oldCount = loadPhotos.pictures.Count;
            loadPhotos.LoadMoreItems(Constants.LOADNEXTITEMSTHRESHHOLD);
            mRecyclerView.Post(() => {
                int newItemsCount = loadPhotos.pictures.Count - oldCount;
                mAdapter.NotifyItemRangeInserted(oldCount, newItemsCount);
            });
        }, 100);
        return;
    }

    // Normal load flow when RecyclerView is idle
    int oldCount = loadPhotos.pictures.Count;
    loadPhotos.LoadMoreItems(Constants.LOADNEXTITEMSTHRESHHOLD);
    mRecyclerView.Post(() => {
        int newItemsCount = loadPhotos.pictures.Count - oldCount;
        mAdapter.NotifyItemRangeInserted(oldCount, newItemsCount);
    });
};

3. Tweak your scroll listener's trigger threshold
   Double-check how your XamarinRecyclerViewOnScrollListener decides when to fire LoadMoreEvent. On the S8's longer screen, the threshold might be triggering too early (while the list is still scrolling). Adjust it to fire only when fewer items remain below the visible viewport, or set it to trigger only after scrolling has stopped.

These changes should eliminate the conflict between RecyclerView's layout computation and your adapter updates, fixing the error on the S8 while keeping things smooth on other devices.

内容的提问来源于stack exchange，提问作者innomotion media