Android 中 RecyclerView 4级嵌套例程

在 Android 中，RecyclerView 的嵌套使用也是比较常见的，可以实现复杂的列表布局。下面是一个四级嵌套的例程：

1. 创建四个不同的 RecyclerView.Adapter

首先，我们需要创建四个不同的 RecyclerView.Adapter，分别是最外层、第二层、第三层和最内层的 Adapter。

最外层Adapter的代码示例：

public class OuterAdapter extends RecyclerView.Adapter<OuterAdapter.OuterViewHolder> {

    private List<SecondAdapter> mSecondAdapters;

    public OuterAdapter(List<SecondAdapter> secondAdapters) {
        mSecondAdapters = secondAdapters;
    }

    @NonNull
    @Override
    public OuterViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_outer, parent, false);
        return new OuterViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull OuterViewHolder holder, int position) {
        holder.bind(mSecondAdapters.get(position));
    }

    @Override
    public int getItemCount() {
        return mSecondAdapters.size();
    }

    static class OuterViewHolder extends RecyclerView.ViewHolder {

        private RecyclerView mSecondRecyclerView;

        OuterViewHolder(@NonNull View itemView) {
            super(itemView);
            mSecondRecyclerView = itemView.findViewById(R.id.second_recycler_view);
            mSecondRecyclerView.setLayoutManager(new LinearLayoutManager(itemView.getContext()));
        }

        void bind(SecondAdapter adapter) {
            mSecondRecyclerView.setAdapter(adapter);
        }
    }
}

第二层、第三层和最内层的 Adapter 代码类似，只需要根据对应的布局和数据类型进行修改即可。

2. 在最外层 RecyclerView 中设置第二层 Adapter

在最外层 RecyclerView 中，我们需要将第二层的 Adapter 设置到对应的 ViewHolder 中。

最外层 RecyclerView 的代码示例：

public class MainActivity extends AppCompatActivity {

    private RecyclerView mOuterRecyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mOuterRecyclerView = findViewById(R.id.outer_recycler_view);
        mOuterRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        List<SecondAdapter> secondAdapters = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            SecondAdapter secondAdapter = new SecondAdapter();
            secondAdapters.add(secondAdapter);
        }

        OuterAdapter outerAdapter = new OuterAdapter(secondAdapters);
        mOuterRecyclerView.setAdapter(outerAdapter);
    }
}

3. 在第二层 RecyclerView 中设置第三层 Adapter

在第二层 RecyclerView 中，我们需要将第三层的 Adapter 设置到对应的 ViewHolder 中。同样地，在第三层 RecyclerView 中设置最内层的 Adapter。

第二层 RecyclerView 的代码示例：

public class SecondAdapter extends RecyclerView.Adapter<SecondAdapter.SecondViewHolder> {

    private List<ThirdAdapter> mThirdAdapters;

    public SecondAdapter() {
        mThirdAdapters = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            ThirdAdapter thirdAdapter = new ThirdAdapter();
            mThirdAdapters.add(thirdAdapter);
        }
    }

    @NonNull
    @Override
    public SecondViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_second, parent, false);
        return new SecondViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull SecondViewHolder holder, int position) {
        holder.bind(mThirdAdapters.get(position));
    }

    @Override
    public int getItemCount() {
        return mThirdAdapters.size();
    }

    static class SecondViewHolder extends RecyclerView.ViewHolder {

        private RecyclerView mThirdRecyclerView;

        SecondViewHolder(@NonNull View itemView) {
            super(itemView);
            mThirdRecyclerView = itemView.findViewById(R.id.third_recycler_view);
            mThirdRecyclerView.setLayoutManager(new LinearLayoutManager(itemView.getContext()));
        }

        void bind(ThirdAdapter adapter) {
            mThirdRecyclerView.setAdapter(adapter);
        }
    }
}

4. 在第三层 RecyclerView 中设置最内层 Adapter

第三层 RecyclerView 的代码示例：

public class ThirdAdapter extends RecyclerView.Adapter<ThirdAdapter.ThirdViewHolder> {

    private List<String> mItems;

    public ThirdAdapter() {
        mItems = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            mItems.add("Item " + i);
        }
    }

    @NonNull
    @Override
    public ThirdViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_third, parent, false);
        return new ThirdViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull ThirdViewHolder holder, int position) {
        holder.bind(mItems.get(position));
    }

    @Override
    public int getItemCount() {
        return mItems.size();
    }

    static class ThirdViewHolder extends RecyclerView.ViewHolder {

        private TextView mTextView;

        ThirdViewHolder(@NonNull View itemView) {
            super(itemView);
            mTextView = itemView.findViewById(R.id.text_view);
        }

        void bind(String item) {
            mTextView.setText(item);
        }
    }
}

以上就是 RecyclerView 四级嵌套的例程，如果需要更多嵌套层级，可以按照同样的方式进行扩展。