No adapter attached; skipping layout _____ AndroidX RecyclerView

Question

I am trying to get a list of posts to display on a RecyclerView in a fragment in Android Studio using Java I do have the ".setAdapter()" code displayed but I am still receiving this error message and I have been stuck on this for a week. I am sure it is something Stupid but here is my fragment, my adapter, and the XML file for the fragment

Fragment

import android.os.Bundle;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;


import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.example.zapster_picture_sharing.Adapter.PostAdapter;
import com.example.zapster_picture_sharing.Model.Post;
import com.example.zapster_picture_sharing.R;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;


public class HomeFragment extends Fragment {
    private RecyclerView recyclerView;
    private PostAdapter postAdapter;
    private List<Post> postLists;


    private List<String> followingList;

    ProgressBar progressBar;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_home, container, false);

        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext());
        linearLayoutManager.setReverseLayout(true);
        linearLayoutManager.setStackFromEnd(true);

        progressBar = view.findViewById(R.id.progress_circular);
        checkFollowing();

        recyclerView = view.findViewById(R.id.recycler_view_story);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

        postLists = new ArrayList<>();
        postAdapter = new PostAdapter(getContext(), postLists, true);
        recyclerView.setAdapter(postAdapter);

        return view;
    }
    private void checkFollowing(){
        followingList = new ArrayList<>();
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Follow")
                .child(FirebaseAuth.getInstance().getCurrentUser().getUid())
                .child("following");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                followingList.clear();
                for(DataSnapshot snapshot:dataSnapshot.getChildren()){
                    followingList.add(snapshot.getKey());

                }
                readPosts();

            }
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
            }
        });
    }
    private void readPosts(){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts");

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                postLists.clear();
                for(DataSnapshot snapshot: dataSnapshot.getChildren()){
                    Post post = snapshot.getValue(Post.class);
                    for(String id:followingList){
                        if(post.getPublisher().equals(id)){
                            postLists.add(post);
                        }
                    }
                }
                postAdapter.notifyDataSetChanged();

                progressBar.setVisibility(View.GONE);

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
            }
        });
    }
}

PostAdapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

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

import com.bumptech.glide.Glide;
import com.example.zapster_picture_sharing.Model.Post;
import com.example.zapster_picture_sharing.Model.User;
import com.example.zapster_picture_sharing.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.List;

public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {

    public Context mContext;
    public List<Post> mPosts;

    //private FirebaseUser firebaseUser;

    public PostAdapter(Context mContext, List<Post> mPosts, boolean b){
        this.mContext = mContext;
        this.mPosts = mPosts;

    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.post_item, viewGroup, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder viewHolder, final int i) {

        //firebaseUser = FirebaseAuth.getInstance().getCurrentUser();

        final Post post = mPosts.get(i);

        Glide.with(mContext).load(post.getPostimage()).into(viewHolder.post_image);

        if (post.getDescription().equals("")){
            viewHolder.description.setVisibility(View.GONE);
        } else {
            viewHolder.description.setVisibility(View.VISIBLE);
            viewHolder.description.setText(post.getDescription());
        }

        publisherInfo(viewHolder.image_profile, viewHolder.username, viewHolder.publisher, post.getPublisher());
    }

    @Override
    public int getItemCount() {
        return mPosts.size();
    }

    public static class ViewHolder extends RecyclerView.ViewHolder{

        public ImageView image_profile, post_image, like, comment, save;
        public TextView username, likes, publisher, description, comments;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            image_profile = itemView.findViewById(R.id.image_profile);
            post_image = itemView.findViewById(R.id.post_image);
            comments = itemView.findViewById(R.id.comments);
            like = itemView.findViewById(R.id.like);
            comment = itemView.findViewById(R.id.comment);
            save = itemView.findViewById(R.id.save);
            username = itemView.findViewById(R.id.username);
            likes = itemView.findViewById(R.id.likes);
            publisher = itemView.findViewById(R.id.publisher);
            description = itemView.findViewById(R.id.description);
        }
    }

    private void publisherInfo(final ImageView image_profile, final TextView username, final TextView publisher, final String userid){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(userid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                User user = dataSnapshot.getValue(User.class);
                Glide.with(mContext).load(user.getImageurl()).into(image_profile);
                username.setText(user.getUsername());
                publisher.setText(user.getUsername());
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
}

XML for the fragment

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Fragment.HomeFragment">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?android:attr/windowBackground">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="?android:attr/windowBackground">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

                <ImageView
                    android:layout_width="180dp"
                    android:layout_height="35dp"
                    android:src="@drawable/zapster_logo"
                    android:id="@+id/logo"
                    android:layout_marginLeft="-20dp"
                    android:layout_alignParentLeft="true"
                    android:layout_alignParentStart="true" />

                <ImageView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginRight="10dp"
                    android:src="@drawable/ic_inbox"
                    android:layout_alignParentRight="true"
                    android:layout_alignParentEnd="true" />



            </RelativeLayout>



        </androidx.appcompat.widget.Toolbar>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/bar">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <androidx.recyclerview.widget.RecyclerView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/recycler_view_story"
                android:layout_margin="5dp"
                android:layout_below="@id/bar"/>

            <androidx.recyclerview.widget.RecyclerView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/recycler_view"
                android:layout_below="@id/recycler_view_story"/>

        </LinearLayout>

    </androidx.core.widget.NestedScrollView>

    <ProgressBar
        android:id="@+id/progress_circular"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"/>

</RelativeLayout>

Post Model

package com.example.zapster_picture_sharing.Model;

public class Post {
    private String postid;
    private String postimage;
    private String description;
    private String publisher;

    public Post(String postid, String postimage, String description, String publisher){
        this.postid = postid;
        this.postimage = postimage;
        this.description = description;
        this.publisher = publisher;
    }

    public Post(){
    }

    public String getPostid() {
        return postid;
    }

    public void setPostid(String postid) {
        this.postid = postid;
    }

    public String getPostimage() {
        return postimage;
    }

    public void setPostimage(String postimage) {
        this.postimage = postimage;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getPublisher() {
        return publisher;
    }

    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }
}

Answer 1

You are re-initializing postsList after calling your checkFollowing() method.

try

postLists = new ArrayList<>();
postAdapter = new PostAdapter(getContext(), postLists, true);
recyclerView.setAdapter(postAdapter);

checkFollowing();

Answer 2

require add setLayoutManager

postAdapter = new PostAdapter(getContext(), postLists, true);
recyclerView.setAdapter(postAdapter);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView#setLayoutManager(androidx.recyclerview.widget.RecyclerView.LayoutManager)

Answer 3

In the XML, there are actually two instances of androidx.recyclerview.widget.RecyclerView.

But in your code, you only attach an adapter to one of them, which causes this warning.