addOnScrollListener 的 RecyclerView onScrolled 方法只调用一次

Question

背景：

我正在通过添加addOnScrollListener 函数来使用RecyclerView 实现分页逻辑。

面临的问题：

onScrolled 方法在 RecyclerView 适配器加载时调用一次，dy 值为 0。但是，当列表在滚动时到达末尾时，onScrolled 方法不会被触发，而onScrollStateChanged 触发正确。

这是我的适配器：

HistoryAdapter(Context context, ArrayList<HistoryItem> items, RecyclerView recyclerView) {
        inflater = LayoutInflater.from(context);
        this.items = items;
        preferences = PreferenceManager.getDefaultSharedPreferences(context);
        this.context = context;
        this.recyclerView = recyclerView;

        final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();

        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                Timber.w("onScrolled.. %s", dy);

                if (dy > 0) {
                    totalItemCount = linearLayoutManager.getItemCount();
                    lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
                    Timber.e("totalItemCount: %s", totalItemCount);
                    Timber.e("lastVisibleItem: %s", lastVisibleItem);

                    if (!isLoading && totalItemCount <= (lastVisibleItem + 1)) {

                        Timber.i("End reached...");
                        if (onLoadMoreListener != null) {
                            //Log.i(TAG, "Episodes Adapter: onLoadMore calling...");
                            onLoadMoreListener.onLoadMore();
                        }
                        isLoading = true;
                    }
                }
            }

            @Override
            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);

            }
        });
    }

回收商：

private void setupRecycler() {
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(linearLayoutManager);
        historyAdapter = new HistoryAdapter(getActivity(), historyItems, recyclerView);
        recyclerView.setAdapter(historyAdapter);
        historyAdapter.setClickListener(this);
        historyAdapter.setOnLoadMoreListener(this);
        historyAdapter.setErrorClickListener(this);
    }

我的回收站 xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/medium_text_color_blue"
        android:padding="12dp">

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="start"
            android:text="#"
            android:textColor="@android:color/white"
            android:textStyle="bold" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="4.5"
            android:gravity="start"
            android:text="CLASS"
            android:textAllCaps="true"
            android:textColor="@android:color/white"
            android:textStyle="bold" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"
            android:gravity="center"
            android:text="Date"
            android:textAllCaps="true"
            android:textColor="@android:color/white"
            android:textStyle="bold" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"
            android:gravity="center"
            android:text="time"
            android:textAllCaps="true"
            android:textColor="@android:color/white"
            android:textStyle="bold" />
    </LinearLayout>

    <FrameLayout
        android:layout_below="@+id/header"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/no_reflection_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:visibility="gone"
            android:layout_gravity="center"
            android:text="No Reflection History found!" />

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/history_recycler"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </FrameLayout>
</RelativeLayout>

我研究过的内容：

StackOverflow 上已经发布了许多此类问题，但其中大多数都指向一个解决方案，即删除 RecyclerView 的父 ScrollView，它正在停止触发 onScrolled 方法，但这似乎不是我面临的问题。

RecyclerView.onScrolled() not getting called

RecyclerView onScrolled not called when use scrollToPosition

RecyclerView onScrolled not being fired at all

RecyclerView not calling onScrolled at the bottom

android RecyclerView onScrolled not call

https://github.com/passsy/ArrayAdapter/issues/4

Answer 1

另一种方法是检查回收器是否可以垂直滚动，如果不能，则表示它已到达底部。

试试这个

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                super.onScrollStateChanged(recyclerView, newState)

                if (!recyclerView.canScrollVertically(1)) {
                    // Load more
                }
            }
}

`