Question

我的应用中有一个RecyclerView与FirestoreRecyclerAdapter一起工作。 ViewHolders实现了一个可扩展的“快速操作”菜单，该菜单在点按项目时即会扩展，理想的行为是一次仅扩展一个项目。扩展一项将使适配器中的所有其他项折叠。

如果屏幕上没有足够的项目适合所有项目，则可以正常工作。但是，如果列表扩展到屏幕外，则当我尝试遍历适配器的项目时，当分离的或屏幕外的ViewHolders尝试调用NullPointerException时，会抛出getParent()。

我该如何遍历适配器中的所有ViewHolder，或者仅遍历可见的？

相关的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);
    }

}

谢谢！

编辑：正如Gilberto所指出的，这非常昂贵。结合了Andrew版本的解决方案：

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。您只需要保存扩展视图的索引并调用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

通过遍历i < recyclerView.getChildCount()并确保清除onViewRecycled(ViewHolder holder)中的VH来解决：

@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;
}

如何在RecyclerView中处理可扩展ViewHolders？

3 个答案: