RecyclerView - get all existing views/viewholders

Question

I want to update the RecyclerView while it's displaying data, in my case, I show images with or without labels.

Defaultly I set the visibility of the label when I create the view holder and that's fine, but I want the user to change the labels visibility through the menu while the RecyclerView is shown, so I want to manually update the visibility for all existing views in the RecyclerView.

Can I somehow get all existing Views? I need all, not only the visible ones, I don't want that a later recycled View is not updated...

Answer 1

First you need to get all the views' indices that are shown, and then you need to go over each, and use the viewHolder of each view:

final int firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition();
final int lastVisibleItemPosition = layoutManager.findLastVisibleItemPosition();
for (int i = firstVisibleItemPosition; i <= lastVisibleItemPosition; ++i) {
    ViewHolder holder = (ViewHolder) mRecyclerView.findViewHolderForAdapterPosition(i);
    ...
    }

---

EDIT: seems it doesn't always return all ViewHolders you might want to handle. This seems like a more stable solution:

for (int childCount = recyclerView.getChildCount(), i = 0; i < childCount; ++i) {
   final ViewHolder holder = recyclerView.getChildViewHolder(recyclerView.getChildAt(i));
   ...
   }

Note: on some cases, you might want to set the number of Views being cached to be large enough so that you will always get the same views recycled, instead of new ones. For this, you can use something like that:

fun RecyclerView.setMaxViewPoolSize(maxViewTypeId: Int, maxPoolSize: Int) {
    for (i in 0..maxViewTypeId)
        recycledViewPool.setMaxRecycledViews(i, maxPoolSize)
}

Example usage:

recyclerView.setMaxViewPoolSize(MAX_TYPE_ITEM, Int.MAX_VALUE)

Answer 2

• Updating the whole adapter list size with notifyDataSetChanged() is not convenient.
• Getting all the current RecyclerView childs (ie. all visible items) is not enough: there are bound view holders that are not visible: after loading at startup usually there are 2 or 3 items bound over the last visible position (depending by your LayoutManager).

---

I just experimented watching the logs i put, that RV binds more items that are not visible, indeed I found no way to retrieve them. I ended up to cache in a Set or List those ViewHolders in onBindViewHolder() and to uncache them in onViewRecycled():

private Set<AbstractViewHolder> mBoundViewHolders = new HashSet<>();
private int mVisibility = View.VISIBILE;

// So you can have access from the Activity/Fragment
public Set<AbstractViewHolder> getAllBoundViewHolders() {
    return Collections.unmodifiableSet(mBoundViewHolders);
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position, List payloads) {
    // Binding code
    ...
    holder.view.setVisibility(mVisibility);

    // Caching VH
    mBoundViewHolders.add((AbstractViewHolder) holder);
}

@Override
public void onViewRecycled(RecyclerView.ViewHolder holder) {
    // Uncaching VH
    mBoundViewHolders.remove(holder);
}

// Your method becomes
public void updateVisibility(int visibility) {
    mVisibility = visibility;
    for (AbstractViewHolder holder : mBoundViewHolders) {
        holder.updateVisibility(visibility);
    }
}

Implement your interface or abstract ViewHolder so you can call your method. In this way you have access to your ViewHolder content.

---

This is what I do in my FlexibleAdapter to unselect the items without invoking the notifyItemRangeChanged(). And if user has animations, all are executed, plus the background changes too when I invoke my method toggleActivation().

If you know a better way to retrieve all bound VH, let me know.

Answer 3

In adapter class:

Boolean isVisible = false;

public CustomAdapter(boolean isVisible) {
    this.isVisible= isVisible;
}
    @Override
    public void onBindViewHolder(ViewHolder holder, final int position) {
     ...

         if (isVisible){
           //setVisibility(View.VISIBLE)
         }else{
         //setVisibility(View.INVISIBLE
         }
    }

public void updateVisibility(boolean newValue){
 isVisible= newValue;
}

In Activity where you want to update the value where the adapter is instantiated:

adapter.updateVisibility(false);
adapter.notifydataSetChanged();

Answer 4

The all existing views are the ones visible, plus some views cached by RecyclerView. You may access all visible Views like that:

View child;
for (int i = 0; i < mRecycler.getChildCount(); i++) {
    child = mRecycler.getChildAt(i);
    //In case you need to access ViewHolder:
    mRecycler.getChildViewHolder(child);
}

Even if you access cached Views they're not bound to data yet, so you won't know if label should be visible or not. Simply set label visibility of remaining Views in onBindViewHolder.

The rest of the Views simply doesn't exist yet, so you can't change anything about them, even if it's the same label visibility state for all of them.

Answer 5

All of the above solutions gives only the visible holders but in reality there are 2-3 other holders that are bound but not visible. To get those as well, the simplest and the accurate way I can think of to get all the holders is:

int lastBoundHolderPosition = -1;
int lastDetachedHolderPosition = -1;

public void onBindViewHolder(final MyViewHolder holder, int position) {
    lastBoundHolderPosition = position;
    //Your implementation
}
public void onViewDetachedFromWindow(MyViewHolder holder){
    lastDetachedHolderPosition = holder.holder.getAdapterPosition();
}

When you want all the adapters visible (plus Bound but not visible):

if(lastDetachedHolderPosition == -1){
    for(pos = 0; pos <= lastDetachedHolderPosition; pos++){
        ViewHolder holder = (ViewHolder) mRecyclerView.findViewHolderForAdapterPosition(pos);
    }
}else{
    if(lastBoundHolderPosition > lastDetachedHolderPosition){ //Scroll down
        //get all the bound holders
        for(int pos = lastDetachedHolderPosition + 1; pos <= lastBoundHolderPosition; pos++){
            ViewHolder holder = (ViewHolder) mRecyclerView.findViewHolderForAdapterPosition(pos);
        }
    }else{ //Scroll up
        //get all the bound holders
        for(int pos = lastBoundHolderPosition ; pos <= lastDetachedHolderPosition-1; pos++){
            ViewHolder holder = (ViewHolder) mRecyclerView.findViewHolderForAdapterPosition(pos);
        }

    }
}