我有一个RecyclerView
在我的应用程序中使用FirestoreRecyclerAdapter
。 ViewHolders
实现了一个可扩展的“快速操作”菜单,该菜单可以在点击项目时进行扩展,理想的行为是一次只扩展一个项目。扩展一个项目应该折叠适配器中的所有其他项目。
当没有足够的项目可以在屏幕上显示它们时,这很好。但是如果列表在屏幕外扩展,当我尝试迭代适配器的项目时,当分离或屏幕外的ViewHolders尝试调用NullPointerException
时,我会得到一个getParent()
。
如何迭代适配器中的所有ViewHolders,或者只迭代可见的ViewHolders?
相关适配器代码:
@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 < mAdapter.getItemCount(); i++) {
if (i != position) {
// ERROR THROWN HERE
BrewViewHolder vh = ((BrewViewHolder) recyclerView.getChildViewHolder(recyclerView.getChildAt(i)));
vh.expanded = false;
}
}
holder.expanded = !holder.expanded;
notifyItemChanged(position);
});
}
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);
}
}
提前致谢!
编辑:正如Gilberto所指出的,这是非常昂贵的。使用Andrew解决方案的版本:
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());
});
}
您不应该迭代所有视图。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);
}
}
如果(vh!= null){vh.expanded(false);}
要么
使用try,catch)))
通过迭代i < recyclerView.getChildCount()
并确保在onViewRecycled(ViewHolder holder)
中清理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;
}