How to update specific item range in recyclerview adapter

I have a recyclerView. I'm fetching a list from server and show it in my list. I have pagination and when I scroll to bottom, I request the server to get next e.g. 50 items. The only problem is, when I get the response, I'm updating the whole adapter, using notifyDataSetChanged().

mViewModel.getList().observe(
			getViewLifecycleOwner(),
			listResult -> {
				recycler.getAdapter().notifyDataSetChanged();
			});

That's simple, I'm using ViewModel. When my observer notifies, I call notifyDataSetChanged(). My adapter gets the list from ViewModel. And when I'm getting next 50 items from server, I just add the new items to an existing list. And after calling notifyDataSetChanged() adapter updates the whole list with this new 50 items. So how can I update only the last 50 items, that I get from server? When I add this items into list, I need to notify adapter to update its data. There I found one notifyItemInserted();, but it needs position.

You can use DiffUtils With AsyncListDiffer to do the work(I am telling you this but I do not properly understand how it works internally). It makes the drawing easy and handled by the Android System. I have read and found on some posts that AsyncListDiffer checks for new Items and only draw the items that are new.

Here is some codes to help you:

Adapter Class

import android.content.Context;
import android.content.Intent;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.AsyncListDiffer;
import androidx.recyclerview.widget.DiffUtil;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.SortedSet;

import neilsayok.github.launchertest5.R;
import neilsayok.github.launchertest5.adapter.viewholder.AppDrawerItemVH;
import neilsayok.github.launchertest5.data.AppInfo;

public class AppDrawerRVAdapter extends RecyclerView.Adapter<AppDrawerItemVH> {


    private Context context;

    private AsyncListDiffer<AppInfo> appList;


    public AppDrawerRVAdapter(Context context) {
        this.context = context;
        appList = new AsyncListDiffer<>(this, new DiffUtil.ItemCallback<AppInfo>() {

            @Override
            public boolean areItemsTheSame(@NonNull AppInfo oldItem, @NonNull AppInfo newItem) {
                return TextUtils.equals(oldItem.getPackageName(), newItem.getPackageName());
            }

            @Override
            public boolean areContentsTheSame(@NonNull AppInfo oldItem, @NonNull AppInfo newItem) {
                return TextUtils.equals(newItem.getLable(), oldItem.getLable());
            }
        });
    }

    public void submitList(SortedSet<AppInfo> data) {
        appList.submitList(new ArrayList<AppInfo>(data));
    }


    @NonNull
    @Override
    public AppDrawerItemVH onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new AppDrawerItemVH(LayoutInflater.from(context).inflate(R.layout.app_drawer_item,
                parent, false));
    }

    @Override
    public void onBindViewHolder(@NonNull AppDrawerItemVH holder, int position) {
        final AppInfo app = appList.getCurrentList().get(position);
        holder.getAppIcon().setImageDrawable(app.getAppIcon());
        holder.getAppLable().setText(app.getLable());

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent launchIntent = context.getPackageManager().getLaunchIntentForPackage(app.getPackageName());
                context.startActivity(launchIntent);
            }
        });
    }

    @Override
    public int getItemCount() {
        if (appList == null)
            return 0;
        else
            return appList.getCurrentList().size();    }
}

AppInfo Class (This is my POJO class just given for reference)

import android.graphics.drawable.Drawable;

public class AppInfo {
    private String lable;
    private String packageName;
    private Drawable appIcon;

    public AppInfo() {
    }

    public AppInfo(String lable, String packageName, Drawable appIcon) {
        this.lable = lable;
        this.packageName = packageName;
        this.appIcon = appIcon;
    }

    public String getLable() {
        return lable;
    }

    public void setLable(String lable) {
        this.lable = lable;
    }

    public String getPackageName() {
        return packageName;
    }

    public void setPackageName(String packageName) {
        this.packageName = packageName;
    }

    public Drawable getAppIcon() {
        return appIcon;
    }

    public void setAppIcon(Drawable appIcon) {
        this.appIcon = appIcon;
    }
}

Change this line in your ViewModel Observer:

recycler.getAdapter().notifyDataSetChanged(); to appDrawerRVAdapter.submitList(appInfos); where appDrawerRVAdapter is the adapter object.

With this method you will not have to call notifydatachanged() or something like that too.This Link helped me a lot.