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RecyclerView findViewHolderForAdapterPosition() returns null even though associated row hasn't been recycled

I am using the RecyclerView from androidx (see here).
I am finding that when a row of my RecyclerView has scrolled off screen, recyclerView.findViewHolderForAdapterPosition() for the associated position returns null (as expected).
But what is not expected is that the associated row hasn't yet been recycled. I am checking this by overriding RecyclerView.Adapter.onViewRecycled() and seeing what is recycled.
So why is a null ViewHolder returned for a row that hasn't been recycled?
And a related question is: how do I find those rows that haven't yet been recycled (apart from keeping a list myself using onViewRecycled())?
The relevant code I'm using is as follows:
In my Activity:
// find the row (ViewHolder) for row with specified 'tag'
int position = customAdapter.getPositionForTag(tag);
ViewHolder viewHolder = recyclerView.findViewHolderForAdapterPosition(position);
// viewHolder above is null even if the associated row (with same 'tag') hasn't been recycled yet
In my CustomAdapter, which extends RecyclerView.Adapter:
int getPositionForTag(String tag) {
for (int i = 0; i < dataSet.size(); i++) {
if (dataSet.get(i).getTag().equals(tag)) {
return i;
}
}
return -1;
}
#Override
public void onViewRecycled(#NonNull ViewHolder holder) {
// here I monitor which rows are recycled
// I add the 'tag' to the ViewHolder as a convenience, when binding ViewHolder (see below)
Log.d(TAG, "onViewRecycled for tag: " + holder.tag);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
// add tag to holder as a convenience...
holder.tag = dataSet.get(position).getTag();
// ... now setup and add views to holder
}

How to make RecyclerView stops recycling defined positions?

My problem is: I have a video streaming happening on one of the views inside the RecyclerView.
When the user scrolls, the view gets recycled and other cameras starts their own streaming on that recycled viewholder. This is bad for user interface since the streaming process takes some seconds to start.
How can I say to the RecyclerView: "Hey Recycler, please, do not recycle that exact position x and give that position ALWAYS the same viewholder you gave it the first time, instead of random one"?
Please someone help me =(

In your getItemViewType(int position) method of adapter, assign unique values for each video, so it will always return same ViewHolder for same video as you wish.
return unique positive number as type for each video type (here i used the adapter position as unique key)
return negative numbers for any non-video items. (nothing special here, just to avoid conflicts with video items, we use negative numbers for non-video items)
I hope you get the idea. cheers :)
#Override
public int getItemViewType(int position) {
// Just as an example, return 0 or 2 depending on position
// Note that unlike in ListView adapters, types don't have to be contiguous
if(dataList.get(position).isVideo()){
return position;
}else{
return -1;//indicates general type, if you have more types other than video, you can use -1,-2,-3 and so on.
}
}
#Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
switch (viewType) {
case -1: View view1 = LayoutInflater.from(parent.getContext())
.inflate(R.layout.general_item, parent, false);
return new GeneralViewHolder(view1);
default:View view2 = LayoutInflater.from(parent.getContext())
.inflate(R.layout.video_item, parent, false);
return new VideoViewHolder(view2);
}
}

Perform viewHolder.setIsRecyclable(false) on the ViewHolder you want not to be recycled.
From docs of ViewHolder#setIsRecyclable(boolean):
Informs the recycler whether this item can be recycled. Views which are not recyclable will not be reused for other items until setIsRecyclable() is later set to true.
This will cause only one ViewHolder to be created.
public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
...
#Override
public void onViewAttachedToWindow(final RecyclerView.ViewHolder holder) {
if (holder instanceof VideoViewHolder) {
holder.setIsRecyclable(false);
}
super.onViewAttachedToWindow(holder);
}
#Override
public void onViewDetachedFromWindow(final RecyclerView.ViewHolder holder) {
if (holder instanceof VideoViewHolder){
holder.setIsRecyclable(true);
}
super.onViewDetachedFromWindow(holder);
}
...
}

RecyclerView uses one view multiple times, when it contains the list which is not displaying on the screen at a time(means a list contain large amount of items which is not displaying on screen at same time you need to scroll up and down). When user scroll the list the offscreen items are reused to display the remaining list items which is called recycling.
To Stop recycling the items call this method in your onBindViewHolder method:
viewHolder.setIsRecyclable(false);
This statement stop the recycling the views.
To Start recycling the items call this method in your onBindViewHolder method:
viewHolder.setIsRecyclable(true);
I hope this will solve your problem.
Thanks

Your problem comes from the viewholder itself. Viewholders keep reference to views, while the adapter don't. The adapter keeps the data collection only. So, add a field to the viewholder to keep a reference of the data element you used to populate the view in the viewholder. In other words:
public class SomeViewHolder extends RecyclerView.ViewHolder{
private View view;
private Data data;
public SomeViewHolder(View itemView) {
super(itemView);
view = itemView;
}
public void bindData(Data data){
view.setData(data);
this.data = data;
}
public void setData(Data data){
this.data = data;
}
public Data getData(){
return data;
}
public View getView(){
return view;
}
}
Now, the viewholder know which element of the adapter is using. Therefore, when overriding the binding method in the adapter, you can check if the holder has already bonded with some data, and, if the data contains video, you can avoid the binding and forcefully set an already loaded view.
#Override
public void onBindViewHolder(SomeViewHolder holder, int position) {
//videoViewData is a data field you have to put into the adapter.
//videoView is a view field you have to put into the adapter.
if(adapterData.get(position).equals(videoViewData)){
holder.setView(videoView);
holder.setData(adapterData.get(position));
}else{
holder.bindData(adapterData.get(position));
if(adapterData.get(position).isVideo()){
videoViewData = adapterData.get(position);
videoView = holder.getView();
}
}
}
Finally, you'll have to override the onViewRecycled method in the adapter, so, when a view containing a video gets recycled, you can get the view and put it somewhere else.
public void onViewRecycled(SomeViewHolder holder){
if(holder.getData().isVideo()){
videoViewData = holder.getData().
videoView = holder.getView();
videoView.pauseVideo();
}
}
keep in mind, this can cause some serious leaks if you don't manage the stored view. Also, you have to define methods for telling when your data is video, and a properly defined equals method.

Best way to handle item not to recycle in recyclerview this answer will resolve your problem.
Not to recycle item

Try using this for that particular position:
holder.setIsRecyclable(false);
Hope this may help.

If You are using query, you can use
query.limit(//no of items you want to show in your RecyclerView)
give it a try.
or Plese post your QueryCode

How to get child view from RecyclerView?

I am trying to get child view by position. I could get view when one item is clicked:
rvSellRecords.addOnItemTouchListener(new RecyclerItemClickListener(getActivity(), new RecyclerItemClickListener.OnItemClickListener() {
#Override
public void onItemClick(View view, int position) {
((MainActivity) getActivity()).showSellRecordFragment(position, view);
}
}));
Now I cannot get child view, without click - let's say by position for example:
rvSellRecords.someMagicalMethodWhichReturnsViewByPosition(5);
Question: How to get child view from RecyclerView?
EDIT FOR BOUNTY:
I have RecyclerView to show products list. When I click on it, I am adding new Fragment where I show product information. While opening I am updating toolbar with view from RecyclerView - this is working perfectly:
rvSellRecords.addOnItemTouchListener(new RecyclerItemClickListener(getContext(), new RecyclerItemClickListener.OnItemClickListener() {
#Override
public void onItemClick(View view, int position) {
sellPresenter.onSellRecordSelected(position, view);
}
}));
When I click blue button with "+", I am incrementing quantity by 1.
public void onIncrementButtonClicked(){
sellRecord.setCount(sellRecord.getCount() + 1);
showQuantity();
bus.post(new SellRecordChangedEvent(sellRecord, sellRecordPosition));
}
Then I am posting updated sellRecord to first fragment using EventBus. There I am updating list data. I supposed that updating value(sell) automatically updates adapter. Now I am getting view from adapter using custom method(getView) which was created by me(you can find it below).
#Subscribe
public void onEvent(SellRecordChangedEvent event){
sell.getSellRecords().set(event.getSellRecordPosition(), event.getSellRecord());
sell.recalculate();
int position = event.getSellRecordPosition();
View view = adapter.getView(position);
bus.post(new TransactionTitleChangedEvent(null, view));
}
This is my adapter class - I changed adapter little bit to collect view in list and added method which returns view for respective position:
public class SellRecordsAdapter extends RecyclerView.Adapter<SellRecordsAdapter.ViewHolder> {
.....
.....
.....
List<View> viewList;
public SellRecordsAdapter(List<SellRecord> sellRecordList) {
.....
viewList = new ArrayList<>();
}
.....
.....
.....
#Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {
.....
.....
.....
viewList.add(i, viewHolder.itemView);
}
public View getView(int position){
return viewList.get(position);
}
}
My problem: when I updating view in toolbar, I am getting old view. When quantity is 3, I am getting view with 2. When quantity 10 - view is with 9.
My question: how to get view from recycler view using position of item(without on click listener)?

Use recyclerView.findViewHolderForLayoutPosition(position) or
reyclerView.findViewHolderForAdapterPosition(position) to get the viewholder for postion. Then you can access any child from your viewholder.
Checkout Recyclerview

RecyclerView.ViewHolder holder = recycleView.findViewHolderForAdapterPosition(position);
ImageView imageView = holder.itemView.findViewById(R.id.iv_product);
This is a supplement to #Ravi Teja's answer. You can get the viewHolder from the recyclerView using position of the particular item, then get a particular view from the viewHolder as shown above

You can use RecyclerView's LayoutManager for it.
View view = layoutManager.findViewByPosition(position)

Hope this helps someone:
I was getting null pointer exceptions with:
recyclerView.findViewHolderForAdapterPosition
recyclerView.findViewHolderForItemId
layoutManager.findViewByPosition.
The reason was that there is a slight delay for the viewholder to be created.
I found the solution here: https://stackoverflow.com/a/33414430/7952427

I post an answer because which is really complex to findviews() from RecyclerView.
#Joe: After spending 4hours found one answer. Which gives me the proper view of the index.
mAdapter is adapter of RecyclerView
View v = recyclerView.findViewHolderForItemId(mAdapter.getItemId(index/position)).itemView;
Now just access your views by:
v.findViewById(R.id.edittext) OR any id.

it helped me, make a 100 ms delay before manipulate it, like this:
Handler handler = new Handler();
mHandler.postDelayed(new Runnable() {
#Override
public void run() {
// rcv is my recyclerview
rcvStatus.getChildAt(1).setBackground(getActivity().getResources().getDrawable(R.drawable.disabled));
// or:
rcvStatus.getChildAt(1).setClickable(false);
}
}, 100);

Write this method in adapter.
public Object getItem(int position) {
return yourArrayList.get(position);
}
and you just need to call it like
yourAdapter.getItem(2);
pass your required position.
Hope it solves your problem.

just put this method in your code and you can call it as you likes
void someMagicalMethodWhichReturnsViewByPosition(int position){
//I assumes child views are CardView
CardView c = (CardView)rvSellRecords.getItem(int position);
///optional codes
//////////
}

now I understand your problem. you need to use interface for join recyclerview item and activity.
you must define an interface class like below:
public interface IViewClick {
public void onClickButtonAdd();
}
add this parameter to your adapter class:
private IViewClick mListener;
and initialize it in constructor with value that get from inputs.
when user click on PLUS button, you send event to activity by this line:
mListener.onClickButtonAdd();
in your activity class you must implements IViewClick interface and add your code there, like this:
#Override
public void onClickButtonAdd() {
/// TODO every thing that you want.
/// change your toolbar values.
}
it is not good solution for you.
RecyclerView.ViewHolder holder =
mRecyclerView.findViewHolderForItemId(mAdapter.getItemId(i));

I wouldn't recommend tracking the view list yourself. It could lead to weird issues with item updates, position updates, etc.
Instead on your SellRecordChangedEvent, use findViewHolderForAdapterPosition() instead of adapter.getView().
#Subscribe
public void onEvent(SellRecordChangedEvent event){
sell.getSellRecords().set(event.getSellRecordPosition(), event.getSellRecord());
sell.recalculate();
int position = event.getSellRecordPosition();
View view = yourrecyclerview.findViewHolderForAdapterPosition(position);
bus.post(new TransactionTitleChangedEvent(null, view));
}
http://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#findViewHolderForAdapterPosition(int)
And as a side note, it's better to implement an actual item click listener to the itemView on the ViewHolder instead of using touch listener. There's lots of examples of this online.

So the recyclerview and your product information are in 2 different fragments yes? You are expecting the recyclerview's views to update when they are not even in foreground? also you are changing adapter data item's data at position event.getSellRecordPosition() , but you are not notifying the adapter that its dataset changed, either by adapter.notifyDataSetChanged() or the other notifyItemChanged(position) methods.
I'd modify your onEvent() like so:
#Subscribe
public void onEvent(SellRecordChangedEvent event){
sell.getSellRecords().set(event.getSellRecordPosition(), event.getSellRecord());
sell.recalculate();
int position = event.getSellRecordPosition();
MyViewHolder holder = adapter.onCreateViewHolder(yourRecyclerView, 0);
adapter.onBindViewHolder(holder,position);
View view = adapter.getView(position);
bus.post(new TransactionTitleChangedEvent(null, view));
}
Calling on createViewHolder and next BindViewHolder on your adapter will definitely update the views for that position, then your adapter.getView(position) should return you the latest view.
Here MyViewHolder is your viewholder class and yourRecyclerview, is the reference to your recycler view

for (int i = 0; i < recycler_view.getAdapter().getItemCount(); i++) {
View viewTelefone = recycler_view.getChildAt(i);
}
If you want to replace text on a particular edit text for same position:
for (int i = 0; i < recycler_view.getAdapter().getItemCount(); i++) {
if(adpterPostion==i)
{
View viewTelefone = recycler_view.getChildAt(i);
EditText et_mobile = (EditText) viewTelefone.findViewById(R.id.et_mobile);
et_mobile.setText("1111111");
}
}

How to Keep RecyclerView's Buttons Clicked Respectfully - Android

I have a RecyclerView that is populated with CardViews. On each of the CardViews there is a button, which up votes the post.
Here is what the button looks when it is not pressed,
Here is what the button looks when it is pressed,
My code works for achieving this but I have a problem since it is a RecyclerView. When I scroll down the posts the RecyclerView recycles the previous posts that have been up voted. So a post will show that it was up voted even though a user never up voted it.
How can I keep the buttons pressed respectfully for each CardView?
This is my Adapter
public class DiscoverRecyclerAdapter
extends RecyclerView.Adapter<DiscoverRecyclerAdapter.ViewHolder> {
private String[] mDataset;
Typeface customFont;
// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTitle;
public TextView mVoterCounter;
public ImageButton mVoterButton;
public ViewHolder(android.support.v7.widget.CardView v) {
super(v);
mTitle = (TextView) v.findViewById(R.id.title);
mVoterCounter = (TextView) v.findViewById(R.id.voter_counter);
//Initialize voter button
mVoterButton = (ImageButton)v.findViewById(R.id.voter);
mVoterButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mVoterButton.setImageResource(R.drawable.ic_voter_pressed);
}
});
}
}
// Provide a suitable constructor (depends on the kind of dataset)
public DiscoverRecyclerAdapter(String[] myDataset, Typeface passedFont) {
mDataset = myDataset;
customFont = passedFont;
}
// Create new views (invoked by the layout manager)
#Override
public DiscoverRecyclerAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
// create a new view
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.item_discover, parent, false);
// set the view's size, margins, paddings and layout parameters
return new ViewHolder((android.support.v7.widget.CardView)v);
}
// Replace the contents of a view (invoked by the layout manager)
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mTitle.setText(mDataset[position]);
holder.mTitle.setTypeface(customFont);
holder.mVoterCounter.setTypeface(customFont);
}
// Return the size of your dataset (invoked by the layout manager)
#Override
public int getItemCount() {
return mDataset.length;
}
}

along with mDataset you will also need a boolean array say mIsSelected
now size of this will be equal to size of array mDataSet or create class if you want.
Then in onBindViewHolder do as
if(mIsSelected[position]
mVoterButton.setImageResource(R.drawable.ic_voter_pressed);
else
mVoterButton.setImageResource(R.drawable.ic_voter_unpressed);
and move button onclick inside onBindViewHolder as below
holder.mVoterButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mVoterButton.setImageResource(R.drawable.ic_voter_pressed);
mIsSelected[position] = true;
}
});

You need to clear the previous rows view of all previous data at the beginning of the onBindViewHolder.
In your case it seems you need to clear all the visibility params of the view components to whatever you deem to be the default. After that go ahead and populate the card with the data.
Being that your passed in dataset is only a string you will need to either make a call to your own API to get the up-vote count / status. Or change your dataset to a custom object array that tracks all of the different components you need to setup and record the data of each card.
In short: As the views get recycled you need to clean them up before re-use.

notifyDataSetChanged() gets updated last

I have a Runnable class that calculates model values for my composite list views, in that runnable there's a UI thread inside of a custom thread. There I have adapter's notifyDataSetChanged() call, but after notifyDataSetChanged() I try updating some TextView value in the main layout. The problem is when running TextView gets updated first and only then ListViews and getting updated. That means notifyDataSetChanged() of the Adapter custom class gets updated last which is not suitable for me. Is there any possibility to synchronize those screen updates?
Here's the sample code:
public class TestRunnable implements Runnable {
private TestAdapter adapter;
#Override
public void run() {
Context.runOnUiThread(new Runnable() {
#Override
public void run() {
adapter.notifyDataSetChanged();
MainActivity.setTextViewValue("Something...");
}
});
}
}
public class TestAdapter extends ArrayAdapter<TestModel> {
#Override
public View getView(final int position, View view, ViewGroup parent) {
View row = view;
TestHolder holder;
Boolean rowIsNew = false;
if (row == null) {
rowIsNew = true;
LayoutInflater layoutInflater = ((Activity) context)
.getLayoutInflater();
row = layoutInflater.inflate(layoutResourceId, parent, false);
holder = new TestHolder();
...
row.setTag(holder);
} else {
holder = (TestHolder) row.getTag();
}
TestModel testModel = data.get(position);
holder.property = testModel.property;
...
if (rowIsNew) {
holder.....setTypeface(...);
holder.....setTypeface(...);
}
return row;
}
}

I have revised the source code of ArrayAdapter and I see no way of executing code after it has called the onChanged() on it's observer so my answer would be:
Implement your own even on onChanged() being called
Call ListView.setAdapter with a brand new adapter with the new dataset
P.S. Number 1 is the optimum solution but number 2 is the easy solution, depending on your time and performance requirement use what you need, but I recommend taking some time and implementing Number 1.

I presume your MainActivity.setTextViewValue("Something..."); line is trying to print some data from the adapter and you're getting the old value, is that so?
I'm not 100% sure of this, perhaps someone else can help confirm this, but I think notifyDataSetChanged() only marks the current data on the adapter as dirty, so the adapter will know that it has to refresh the data, but it doesn't do it immediately when you do the call.
EDIT:
If my first paragraph is correct, you should try to update the text view with data from the data source instead of the adapter, this would be a nicer way to solve the problem.