Android 异构 recyclerview 混蛋和数据模型混乱

Question

我有一个包含水平 RecyclerView 和垂直 RecyclerView 的 RecyclerView。我对如何管理两者的数据模型感到困惑。这是我的代码，后面是 example

public class HomeAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private final int VIEW_TYPE_DESIGN_TYPES = 0;
    private final int VIEW_TYPE_DESIGNS = 1;

    private Context context;
    private ArrayList<Object> feeds;

    public HomeAdapter(Context context, ArrayList<Object> feeds) {
        this.context = context;
        this.feeds = feeds;
    }

    @Override
    public int getItemViewType(int position) {
        if (position == 0)
            return VIEW_TYPE_DESIGN_TYPES;
        if (position == 1)
            return VIEW_TYPE_DESIGNS;
        return -1;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view;
        RecyclerView.ViewHolder holder;
        switch (viewType) {
            case VIEW_TYPE_DESIGN_TYPES:
                view = inflater.inflate(R.layout.item_home_design_types, parent, false);
                holder = new DesignTypesViewHolder(view);
                break;
            case VIEW_TYPE_DESIGNS:
                view = inflater.inflate(R.layout.item_home_designs, parent, false);
                holder = new DesignsViewHolder(view);
                break;
            default:
                view = inflater.inflate(R.layout.item_home_designs, parent, false);
                holder = new DesignsViewHolder(view);
                break;
        }
        return holder;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder.getItemViewType() == VIEW_TYPE_DESIGN_TYPES)
            designTypesView((DesignTypesViewHolder) holder);
        else if (holder.getItemViewType() == VIEW_TYPE_DESIGNS)
            designsView((DesignsViewHolder) holder);
    }


    private void designTypesView(DesignTypesViewHolder holder) {
        HomeAdapterDesignTypes homeAdapterDesignTypes = new HomeAdapterDesignTypes(getDesignTypes());
        holder.recyclerView.setAdapter(homeAdapterDesignTypes);
    }

    private void designsView(DesignsViewHolder holder) {
        HomeAdapterDesigns homeAdapterDesigns = new HomeAdapterDesigns(getDesigns());
        holder.recyclerView.setAdapter(homeAdapterDesigns);
    }

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

    public void updateFeeds(ArrayList<Object> mFeeds) {
        feeds.addAll(mFeeds);
        notifyDataSetChanged();
    }

    public class DesignTypesViewHolder extends RecyclerView.ViewHolder {
        RecyclerView recyclerView;
        DesignTypesViewHolder(View itemView) {
            super(itemView);
            recyclerView = itemView.findViewById(R.id.rvHomeDesignTypes);
            recyclerView.setLayoutManager(new LinearLayoutManager(context, LinearLayoutManager.HORIZONTAL, false));
            ItemOffsetDecoration itemDecoration = new ItemOffsetDecoration(context, R.dimen.item_offset);
            recyclerView.addItemDecoration(itemDecoration);
        }
    }

    public class DesignsViewHolder extends RecyclerView.ViewHolder {
        RecyclerView recyclerView;
        DesignsViewHolder(View itemView) {
            super(itemView);
            recyclerView = itemView.findViewById(R.id.rvHomeDesigns);
            recyclerView.setLayoutManager(new GridLayoutManager(context, 2));
            int spanCount = 2;
            int spacing = 15;
            boolean includeEdge = true;
            recyclerView.addItemDecoration(new GridSpacingItemDecoration(spanCount, spacing, includeEdge));
        }
    }

    private ArrayList<DesignType> getDesignTypes() {
        ArrayList<DesignType> singleHorizontals = new ArrayList<>();
        for(int i = 0 ; i < feeds.size(); i++) {
            Object object = feeds.get(i);
            if(object instanceof DesignType) {
                singleHorizontals.add((DesignType) object);
            }
        }
        return singleHorizontals;
    }

    private ArrayList<Design> getDesigns() {
        ArrayList<Design> singleVerticals = new ArrayList<>();
        for(int i = 0 ; i < feeds.size(); i++) {
            Object object = feeds.get(i);
            if(object instanceof Design) {
                singleVerticals.add((Design) object);
            }
        }
        return singleVerticals;
    }
}

现在我的 Horizontal recyclerview 位于位置 0 并且具有静态数据项。 Vertical RecyclerView 是动态的，我想为它实现无限滚动。我不知道如何管理和更新两者的数据模型 (POJO class)。因为两个 Recyclerviews 的对象类型不同。我应该为两者创建一个通用的 POJO class 吗？

我面临的另一个问题是当列表滚动到最后时出现卡顿。

Answer 1

看起来您的父回收视图设计为仅包含两项：

@Override
public int getItemViewType(int position) {
    if (position == 0)
        return VIEW_TYPE_DESIGN_TYPES;
    if (position == 1)
        return VIEW_TYPE_DESIGNS;
    return -1;
}

但是从这里我可以看到，如果您有两个以上的项目 - 您最终会将所有后续持有人创建为 DesignsViewHolder:

default:
            view = inflater.inflate(R.layout.item_home_designs, parent, false);
            holder = new DesignsViewHolder(view);
            break;

如果意图是 - 在网格项目中拥有水平滚动的顶级回收器视图和下一个回收器视图，那么在一个布局中只有两个回收器视图是非常好的。

<ConstraintLayout or ScrollView> - as u wish
  <RecyclerView\> - horizontal one
  <RecyclerView\> - vertical one, or with grid layout manager
<\ConstraintLayout or ScrollView>

编辑：关于你的问题link，我们有一个反之亦然的结构。垂直滚动和水平滚动的最后一项。在这种情况下，您可以切换回收站视图排序。

不过，如果您想在回收站中放置真正不同的物品，请考虑使用 Adapter Delegates 模式。

注意：recycler 视图中有很多不同的滚动方向不容易维护。有时会出现难以修复的差异错误。在某些情况下，更容易结束在回收器视图中有一个滚动视图，而不是 回收视图内的回收视图。 RecyclerView 在底层有一个相当复杂的结构，它优化了性能和项目的可重用性。在大多数情况下，就将此布局与垂直滚动混合而言，您需要一些简单的东西，其中包含 5-10 个用于水平滚动的项目。这里要讨论的东西很多，具体情况视情况而定。

看看 Joe's problem and a nice GitHub lib，这些应该有助于理解 Adapters Delegate 模式。祝你好运！

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