NestedScrollView 内的多个 Recyclerview 不会发生视图回收

Question

我在管理 NestedScrollView 内的多个 Recyclerview 回收时遇到了问题。让我告诉我我想做什么 -

1. 我有两种框架布局，即 frame1 和 frame2。
2. 我有两个包含 recyclerview 的片段，第一个片段的 recyclerview 水平显示项目，而第二个片段的 recyclerview 垂直显示列表。
3. 现在我把FrameLayout 都放在了NestedScroolView 里面，frame1 recyclerview 正在正确回收所有视图，但是 frame2 recyclerview 没有回收视图，不知道为什么？它首先加载所有项目，然后显示在屏幕上。

一些代码：

MainActivity.java

 FragmentTransaction transaction;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
setContentView(R.layout.main);
FragmentA frag1=new FragmentA();
FragmentB frag2=new FragmentB();
transaction =    getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.frame1, frag1);
    transaction.addToBackStack(frag1.getClass().getName());
    transaction.commit();

 transaction =   getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.frame2, frag2);
    transaction.addToBackStack(frag2.getClass().getName());
    transaction.commit();
}

ma​​in.xml

  <LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

 <android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">
  <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <FrameLayout
            android:id="@+id/frame1"
            android:layout_width="match_parent"
            android:layout_height="185dp" />

        <FrameLayout
            android:id="@+id/frame2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
             />

</LinearLayout>
</android.support.v4.widget.NestedScrollView>
    </LinearLayout>

片段A：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View v= inflater.inflate(R.layout.recycler_view, container, false);
    mDataListView = (RecyclerView) v.findViewById(R.id.data_list_view);
    mDataListView .setHasFixedSize(true);
    final GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(), getActivity().getResources().getInteger(R.integer.playlist_categories_columns), GridLayoutManager.VERTICAL, false);

    mDataListView .setNestedScrollingEnabled(false);
   }
    }));


    return v;
}

片段B：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View v= inflater.inflate(R.layout.recycler_view, container, false);
    mDataListView = (RecyclerView) v.findViewById(R.id.data_list_view);
    mDataListView .setHasFixedSize(true);
     final GridLayoutManager gridLayoutManager = new    GridLayoutManager(getActivity(), 1, GridLayoutManager.HORIZONTAL, false);
    mDataListView .setLayoutManager(gridLayoutManager);

    mDataListView .setNestedScrollingEnabled(false);
   }
    }));


    return v;
}

recycler_view.xml

 <?xml version="1.0" encoding="utf-8"?>
 <android.support.v7.widget.RecyclerView    xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/data_list_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />

我希望我的问题很清楚。

Answer 1

根据我的经验，我发现在NestedScrollView 中使用多个recyclerview's 是不可能实现视图回收的。

但我想出了根据我的要求显示多个 Recyclerview 的解决方案，我想在顶部显示一个 Horizo​​ntal Recyclerview，在其下方显示一个 Vertical Recyclerview，所以我分享的内容可能对某人有所帮助。

我删除了NestedScrollView 作为Recyclerview's 的父级，并将水平Recyclerview 设置为垂直HeaderView 的HeaderView。

代码：

public class ListHeaderAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private static final int TYPE_HEADER = 0;
private static final int TYPE_ITEM = 1;
ArrayList<String> data;

public ListHeaderAdapter (ArrayList<String> data) {
    this.data = data;
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    if (viewType == TYPE_ITEM) {
        //inflate your layout and pass it to view holder
        return new VHItem(null);
    } else if (viewType == TYPE_HEADER) {
        //inflate your layout and pass it to view holder
        return new VHHeader(null);
    }
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
 int pos = position - 1; // for handling of Header view(use pos to fetch data from list)

    if (holder instanceof VHItem) {
        String dataItem = data.get(pos);
        //cast holder to VHItem and set data
    } else if (holder instanceof VHHeader) {
        //cast holder to VHHeader and set data for header.
    }
}

@Override
public int getItemCount() {
    return data.size()+ 1; // for handling of Header view
}

@Override
public int getItemViewType(int position) {
    if (isHeader(position))
        return TYPE_HEADER;

    return TYPE_ITEM;
}

public boolean isHeader(int position) {
    return position == 0;
}


class VHItem extends RecyclerView.ViewHolder {
    TextView title;

    public VHItem(View itemView) {
        super(itemView);
    }
}

class VHHeader extends RecyclerView.ViewHolder {
    Button button;

    public VHHeader(View itemView) {
        super(itemView);
    }
}
}

注意：可以实现相同的逻辑以在任何位置显示水平RecyclerView's