How to implement pagination in RecyclerView on scroll

Question

Recyclerview comes with its own scroll listener which has the following methods :

void onScrollStateChanged(RecyclerView recyclerView, int newState)         


        

Answer 1

Make Next Call at the end of scroll

There are essentially 3 steps.

1. Notify when the list is scrolled
2. Make REST call (for NEXT page)
3. Add the result in the old list + Notify DataSet change

CALLBACK

But first, we need a Callback which would work as a bridge between RecyclerView.Adapter and Activity

public interface PaginationCallBack{
     public void oadNextPage();
}

Implement this callback in Your Activity

class YourActivity extends AppCompatActivity implements PaginationCallBack{

     int pageNum = 1;

     @Override
     public void loadNextPage(){
           // Your implementation
     }
}

Initialize Callback in RecyclerView.Adapter

class YourAdapter extends RecyclerView.Adapter{

     private PaginationCallBack paginationCallBack;

     public YourAdapter(PaginationCallBack paginationCallBack) {
        this.paginationCallBack = paginationCallBack;
     }

}

STEP 1 Add a condition in onBindViewHolder method and notify with a Callback.

@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewholder, int position) {

    if(position+1==images.size()){
        paginationCallBack.loadNextPage();  // Callback
    }

}

Step 2: Call NEXT Page

getImages(++pageNum) // YOUR REST method which page number

@Override
public void loadNextPage(){
    getImages(++pageNumber) // REST call with next Page 
}

Step 3 Add the result in old list and notify datasetChanged

public void getImages(int pageNum){

      List newResults = //RESTCALL
      imageList.addAll(newResults);
      adapter.updateDataSet(imageList)

}

Where is updateDataSet(imageList) method?

Write this method inside RecyclerView.Adapter

 public void updateDataSet(List newImages){

    if(newImages!=null){
        images = newImages;
    }

    notifyDataSetChanged();
}

Full Code

RecyclerView Pagination

Result: