Cfrgtkky

I saw a sample code and couldn't understand the meaning of the following method:

public int getAdapterPositionForIndex(RecyclerView parent, int index) {

        final View child = parent.getChildAt(index);

        return parent.getChildAdapterPosition(child);

    }

My understanding is what's returned should always equal to index, but my debugger obviously doesn't say so. Since the docs are not explaining well the difference between getChildAt() and getChildAdapterPostion(), I hope I could get some expert insights here.

Well as per my understanding getChildAt() is a method of ViewGroup . And it does Returns the view at the specified position in the group.

Since RecyclerView is an AdapterView i.e items get recycle when goes out of boundary it returns null for #getChildAt().

I am not sure whats the exact reason may be some should explain this

On other hand #getChildAdapterPosition() Return the adapter position that the given child view added to.
Look at the code below :(Only adding the essential)

findViewById(R.id.b1).setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            LinearLayoutManager layoutManager= (LinearLayoutManager) rvNumber.getLayoutManager();

            final View child = layoutManager.findViewByPosition(30);

            if(child!=null) {

                int i = rvNumber.getChildAdapterPosition(child);

                Log.i("pos", i + "");

            }else{

                Log.i("pos",  "View is null");

            }

        }

    });

Nothing complex here! I laid down 60 items in RecyclerView just a TextView. In which 10 items are showing at a time in list . So the first time 10 views will be laid down (0-9).

When i call the above code on clicking on button it gives me a null view . Cause Views is not inflated yet for position 30. But after scrolling to position 30 it returns the view and hence its position by getChildAdapterPosition() which will be 30 also .

I think you should make a sample and play around with it for better understanding.

FROM DOCS

getChildAdapterPosition()

• Return the adapter position that the given child view corresponds to.

getChildAt()

• Returns the view at the specified position in the group.

The Difference

It Means the getChildAdapterPosition() method return the the position of View inside recyclerview adapter

AND

the getChildAt() method returns the View from a viewGroup of specific position

In short
The Both method are different getChildAt() is retuning view from a viewGroup while the other getChildAdapterPosition() retuning the postion of a view in recyclerview adapter