我想把ListView改为RecyclerView。我想在RecyclerView中使用OnScrollListener的onScroll来确定用户是否滚动到列表的末尾。

我如何知道用户是否滚动到列表的末尾以便我可以从REST服务获取新数据?


当前回答

有一个方法public void setOnScrollListener (RecyclerView。OnScrollListener监听器)在https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#setOnScrollListener%28android.support.v7.widget.RecyclerView.OnScrollListener%29。使用这个

编辑:

在onScrollListener中重写onScrollStateChanged方法并执行此操作

            boolean loadMore = firstVisibleItem + visibleItemCount >= totalItemCount;

            //loading is used to see if its already loading, you have to manually manipulate this boolean variable
            if (loadMore && !loading) {
                 //end of list reached
            }

其他回答

正如约翰·T所建议的。只需使用下面的代码块,真的很简短,美观简单:D

public void loadMoreOnRecyclerView() {
    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(@NonNull @NotNull RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if (!recyclerView.canScrollVertically(1) && dy != 0) {
                //Load more items here
            }
        }
    });
}

你可以跟随我的回购来了解它的工作方式。

https://github.com/Nghien-Nghien/PokeAPI-Java/blob/0d8d69d348e068911b883f0ae7791d904cc75cb5/app/src/main/java/com/example/pokemonapi/MainActivity.java

关于应用程序的描述信息如下:https://github.com/skydoves/Pokedex#readme

有一个方法public void setOnScrollListener (RecyclerView。OnScrollListener监听器)在https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#setOnScrollListener%28android.support.v7.widget.RecyclerView.OnScrollListener%29。使用这个

编辑:

在onScrollListener中重写onScrollStateChanged方法并执行此操作

            boolean loadMore = firstVisibleItem + visibleItemCount >= totalItemCount;

            //loading is used to see if its already loading, you have to manually manipulate this boolean variable
            if (loadMore && !loading) {
                 //end of list reached
            }

对于那些只想在最后一项完全显示时得到通知的人,可以使用view . canscrollvertical()。

这是我的实现:

public abstract class OnVerticalScrollListener
        extends RecyclerView.OnScrollListener {

    @Override
    public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        if (!recyclerView.canScrollVertically(-1)) {
            onScrolledToTop();
        } else if (!recyclerView.canScrollVertically(1)) {
            onScrolledToBottom();
        } else if (dy < 0) {
            onScrolledUp();
        } else if (dy > 0) {
            onScrolledDown();
        }
    }

    public void onScrolledUp() {}

    public void onScrolledDown() {}

    public void onScrolledToTop() {}

    public void onScrolledToBottom() {}
}

注意:如果你想支持API < 14,你可以使用recyclerView.getLayoutManager(). canscrollvertical()。

Create an abstract class and extends RecyclerView.OnScrollListener public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener { private int previousTotal = 0; private boolean loading = true; private int visibleThreshold; private int firstVisibleItem, visibleItemCount, totalItemCount; private RecyclerView.LayoutManager layoutManager; public EndlessRecyclerOnScrollListener(RecyclerView.LayoutManager layoutManager, int visibleThreshold) { this.layoutManager = layoutManager; this.visibleThreshold = visibleThreshold; } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); visibleItemCount = recyclerView.getChildCount(); totalItemCount = layoutManager.getItemCount(); firstVisibleItem = ((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition(); if (loading) { if (totalItemCount > previousTotal) { loading = false; previousTotal = totalItemCount; } } if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) { onLoadMore(); loading = true; } } public abstract void onLoadMore();} in activity (or fragment) add addOnScrollListener to recyclerView LinearLayoutManager mLayoutManager = new LinearLayoutManager(this); recyclerView.setLayoutManager(mLayoutManager); recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager, 3) { @Override public void onLoadMore() { //TODO ... } });

大多数答案是假设RecyclerView使用LinearLayoutManager,或GridLayoutManager,甚至StaggeredGridLayoutManager,或假设滚动是垂直或水平的,但没有人张贴一个完全通用的答案。

使用ViewHolder的适配器显然不是一个好的解决方案。一个适配器可能有超过1个RecyclerView在使用它。它“改编”了它们的内容。它应该是RecyclerView(它是一个负责当前显示给用户的类,而不是适配器,它只负责向RecyclerView提供内容),它必须通知您的系统需要更多的项(加载)。

下面是我的解决方案,只使用了RecyclerView (RecycerView. view)的抽象类。LayoutManager和RecycerView.Adapter):

/**
 * Listener to callback when the last item of the adpater is visible to the user.
 * It should then be the time to load more items.
 **/
public abstract class LastItemListener extends RecyclerView.OnScrollListener {

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

      // init
      RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
      RecyclerView.Adapter adapter = recyclerView.getAdapter();

      if (layoutManager.getChildCount() > 0) {
        // Calculations..
        int indexOfLastItemViewVisible = layoutManager.getChildCount() -1;
        View lastItemViewVisible = layoutManager.getChildAt(indexOfLastItemViewVisible);
        int adapterPosition = layoutManager.getPosition(lastItemViewVisible);
        boolean isLastItemVisible = (adapterPosition == adapter.getItemCount() -1);

        // check
        if (isLastItemVisible)
          onLastItemVisible(); // callback
     }
   }

   /**
    * Here you should load more items because user is seeing the last item of the list.
    * Advice: you should add a bollean value to the class
    * so that the method {@link #onLastItemVisible()} will be triggered only once
    * and not every time the user touch the screen ;)
    **/
   public abstract void onLastItemVisible();

}


// --- Exemple of use ---

myRecyclerView.setOnScrollListener(new LastItemListener() {
    public void onLastItemVisible() {
         // start to load more items here.
    }
}