如何处理 RecyclerView 中的可扩展 ViewHolder？

Question

我的应用程序中有一个 RecyclerView 与 FirestoreRecyclerAdapter 一起工作。 ViewHolders 实现了一个可扩展的 'quick actions' 菜单，该菜单在点击项目时展开，理想的行为是一次只展开一个项目。展开一个项目应该折叠适配器中的所有其他项目。

当屏幕上没有足够的项目来容纳所有项目时，此方法可以正常工作。但是，如果列表延伸到屏幕外，当我尝试遍历适配器的项目时，当分离的或屏幕外的 ViewHolder 尝试调用 getParent().

时，我会抛出 NullPointerException

如何迭代适配器中的所有 ViewHolder，或者仅迭代可见的？

相关ViewHolder代码：

public class BrewViewHolder extends RecyclerView.ViewHolder {

    // Expanded state
    public boolean expanded = false;
    ...

    public BrewViewHolder(@NonNull final View itemView) {
        super(itemView);
        ...
        // Set visibility of quick actions based on expanded state
        quickActions.setVisibility(expanded ? View.VISIBLE : View.GONE);
    }

}

提前致谢！

编辑：作为Gilberto pointed out, this is very expensive. Went with a version of Andrew的解决方案：

private int expandedItemIndex = -1;

@Override
protected void onBindViewHolder(@NonNull BrewViewHolder holder, int position,
                                @NonNull Brew brew) {
    // Bind Views
    holder.bind(brew);

    // Set expander ClickListener
    holder.card.setOnClickListener(v -> {
        if (position == expandedItemIndex) {
            holder.expanded = false;
            expandedItemIndex = -1;
        } else {
            holder.expanded = true;
            if (expandedItemIndex != -1) {
                BrewViewHolder otherHolder = ((BrewViewHolder) recyclerView.getChildViewHolder(
                        recyclerView.getChildAt(expandedItemIndex)));
                otherHolder.expanded = false;
            }
            expandedItemIndex = position;
        }
        notifyItemRangeChanged(0, recyclerView.getChildCount());
    });

}

Answer 1

If(vh!=null){ vh.expanded(false);}

或

使用 try, catch)))

Answer 2

您不应迭代所有视图。您只需要保存展开视图的索引并调用 notifyDataSetChanged 或 notifyItemChanged.

private int expandedItemIndex = -1;

@Override
protected void onBindViewHolder(@NonNull BrewViewHolder holder, 
               final int position, @NonNull Brew brew) {

    // Bind Views
    holder.bind(brew);

    // Set expander ClickListener
    holder.card.setOnClickListener(v -> {
        if (position == expandedItemIndex) {
            notifyItemChanged(position);
            expandedItemIndex = -1;
        } else {
            if (expandedItemIndex != -1) {
                notifyItemChanged(expandedItemIndex);
            }
            expandedItemIndex = position;
            notifyItemChanged(position);
        }
   });

   if (position == expandedItemIndex) {
      // Expand
      holder.quickActions.setVisibility(View.VISIBLE);
   } else {
      // Collapse
      holder.quickActions.setVisibility(View.GONE);
   }
}

Answer 3

通过迭代 i < recyclerView.getChildCount() 并确保清理 onViewRecycled(ViewHolder holder) 中的 VH 解决：

@Override
protected void onBindViewHolder(@NonNull BrewViewHolder holder, int position, @NonNull Brew brew) {
    // Bind Views
    holder.bind(brew);

    // Set expander ClickListener
    holder.card.setOnClickListener(v -> {
        for (int i = 0; i < recyclerView.getChildCount(); i++) {
            if (i != position) {
                BrewViewHolder otherHolder = ((BrewViewHolder) recyclerView.getChildViewHolder(recyclerView.getChildAt(i)));
                otherHolder.expanded = false;
            }
        }
        holder.expanded = !holder.expanded;
        notifyItemRangeChanged(0, recyclerView.getChildCount());
    });
}

@Override
public void onViewRecycled(@NonNull BrewViewHolder holder) {
    super.onViewRecycled(holder);
    holder.expanded = false;
}

如何处理 RecyclerView 中的可扩展 ViewHolder？

How to handle expandable ViewHolders in a RecyclerView?

android

android-viewholder

android-recyclerview