com.google.firebase.database.DatabaseException: Failed to convert value of type java.lang.Long to String...shows error for a specific line

Question

package com.example.stdio9.fragment;

import android.os.Bundle;

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

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

import com.example.stdio9.Adapter.ContentAdapter;
import com.example.stdio9.Models.ContentModel;
import com.example.stdio9.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.ArrayList;
import java.util.Collections;

public class HomeFragment extends Fragment {

    RecyclerView recyclerView;
    ArrayList<ContentModel> list;
    ContentAdapter adapter;

    DatabaseReference reference;


    public HomeFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
       View view = inflater.inflate(R.layout.fragment_home, container, false);

       recyclerView = view.findViewById(R.id.recyclerView);
       recyclerView.setHasFixedSize(true);

       reference = FirebaseDatabase.getInstance().getReference().child("Content");

       getAllVideos();

       return view;
    }

    private void getAllVideos() {
        list = new ArrayList<>();
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                if(snapshot.exists()){
                    list.clear();

                    for(DataSnapshot dataSnapshot: snapshot.getChildren()){
                        ContentModel model = dataSnapshot.getValue(ContentModel.class);
                        list.add(model);
                    }

                    Collections.shuffle(list);

                    adapter = new ContentAdapter(getActivity(),list);
                    recyclerView.setAdapter(adapter);
                    adapter.notifyDataSetChanged();
                }else{
                    Toast.makeText(getActivity(), "No data found", Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Toast.makeText(getActivity(), error.getMessage(), Toast.LENGTH_SHORT).show();

            }
        });
    }
}

This is what the error shows

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.stdio9, PID: 24822 com.google.firebase.database.DatabaseException: Failed to convert value of type java.lang.Long to String at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertString(CustomClassMapper.java:426) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:217) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToType(CustomClassMapper.java:179) at com.google.firebase .database.core.utilities.encoding.CustomClassMapper.access$100(CustomClassMapper.java:48) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.deserialize(CustomClassMapper.java:593) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.deserialize(CustomClassMapper.java:563) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:433) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:232) at com.google.ZB F12E1515C25C7D8C0352F1413AB9A15Z.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:80) at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203) at com.example.stdio9.fragment.HomeFragment$1.onDataChange(HomeFragment.java:65) at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75) at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63) at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55) at ZC31B3236 4CE19CA8FCD150A417ECCE58Z.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:233) at android.app.ActivityThread.main(ActivityThread.java:8068) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:631) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:978)

This is the line which it takes me to

 ContentModel model = dataSnapshot.getValue(ContentModel.class);

This is my JSON File

{
  "Channels": {
    "K3Q3vk5K0KYsXzikFR3ISRI97Np1": {
      "channel_logo": "https://lh3.googleusercontent.com/a/AItbvmmoALgeo1I6QAmFiVRMZzErdjciiykyz8IA3l23=s96-c",
      "channel_name": "Food insider",
      "description": "Food Vlogs",
      "joined": "4 Sep 2022",
      "uid": "K3Q3vk5K0KYsXzikFR3ISRI97Np1"
    },
    "kNFLhugOP1e18pWvMWcdhNfeMjZ2": {
      "channel_logo": "https://lh3.googleusercontent.com/a-/AFdZucqGchXowFwL77eSywfbyeOQbCsotcfoMr9f4cN2Kw=s96-c",
      "channel_name": "Ryan Fernandes",
      "description": "My Life through Vlogs ",
      "joined": "Aug 19, 2022",
      "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2"
    }
  },
  "Content": {
    "-NB16m0MkgzfJ55tkqsW": {
      "date": "Sep 3, 2022",
      "playlist": "Dark Place",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "type": "video",
      "video_description": "Dark Place Juice Wrld - Unreleased",
      "video_tags": "[999 LLJW]",
      "video_title": "Unreleased Song by Juice Wrld",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Content%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662187923103%2Cmp4?alt=media&token=48437c1b-e21d-4f31-9240-b074b59182dd",
      "videoid": "-NB16m0MkgzfJ55tkqsW",
      "views": 0
    },
    "-NB7dlr2Sw-cmKHpy-0s": {
      "date": "Sep 4, 2022",
      "playlist": "999",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "type": "video",
      "video_description": "Juice Wrld Dark Place - Unreleased",
      "video_tags": "[999 LLJW]",
      "video_title": "Unreleased Song by Juice Wrld\n999🖤",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Content%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662297498874%2Cmp4?alt=media&token=a7b262d6-8b63-4ff8-97ee-85a922b8ea71",
      "videoid": "-NB7dlr2Sw-cmKHpy-0s",
      "views": 0
    },
    "-NB7e7_dV8OMG3rzBZ47": {
      "date": "Sep 4, 2022",
      "playlist": "Juice wrld",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "type": "video",
      "video_description": "Robbery - Juice Wrld",
      "video_tags": "[999]",
      "video_title": "Fl Studio",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Content%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662297573502%2Cwebm?alt=media&token=775dfcad-ad30-4d80-87bf-2b6c6e132057",
      "videoid": "-NB7e7_dV8OMG3rzBZ47",
      "views": 0
    },
    "-NBBNYPsjfsRbz4lpHd2": {
      "date": "Sep 5, 2022",
      "playlist": "Juice wrld",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "type": "video",
      "video_description": "The Light",
      "video_tags": "[999]",
      "video_title": "Unreleased",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Content%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662360092449%2Cmp4?alt=media&token=4801e425-8179-4b73-98d7-73c0fa3f2ca9",
      "videoid": "-NBBNYPsjfsRbz4lpHd2",
      "views": 0
    },
    "-NBLMZqiW7xLZ9GPqzGk": {
      "date": "Sep 7, 2022",
      "playlist": "Juice wrld",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "type": "video",
      "video_description": "123",
      "video_tags": "[123]",
      "video_title": "123",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Content%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662527602262%2Cmp4?alt=media&token=33baafb8-1551-4535-89ea-efaf3ba7f854",
      "videoid": "-NBLMZqiW7xLZ9GPqzGk",
      "views": 0
    }
  },
  "Playlists": {
    "kNFLhugOP1e18pWvMWcdhNfeMjZ2": {
      "123": {
        "playlist_name": "123",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 1
      },
      "999": {
        "playlist_name": "999",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 1
      },
      "Dark Place": {
        "playlist_name": "Dark Place",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 1
      },
      "Juice wrld": {
        "playlist_name": "Juice wrld",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 3
      },
      "JuiceWrld": {
        "playlist_name": "JuiceWrld",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 0
      },
      "JuiceWrld ": {
        "playlist_name": "JuiceWrld ",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 0
      },
      "The Light ": {
        "playlist_name": "The Light ",
        "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
        "videos": 0
      }
    }
  },
  "Users": {
    "K3Q3vk5K0KYsXzikFR3ISRI97Np1": {
      "email": "b16sydelle@auxiliumwadala.net",
      "profile": "https://lh3.googleusercontent.com/a/AItbvmmoALgeo1I6QAmFiVRMZzErdjciiykyz8IA3l23=s96-c",
      "search": "sydelle fernandes",
      "uid": "K3Q3vk5K0KYsXzikFR3ISRI97Np1",
      "username": "SYDELLE FERNANDES"
    },
    "QEQmEdSOzXYbRKgdKxltlZUgiGJ2": {
      "email": "fernandesryan1626@gmail.com",
      "profile": "https://lh3.googleusercontent.com/a-/AFdZucqGchXowFwL77eSywfbyeOQbCsotcfoMr9f4cN2Kw=s96-c",
      "search": "ryan fernandes",
      "uid": "QEQmEdSOzXYbRKgdKxltlZUgiGJ2",
      "username": "Ryan Fernandes"
    },
    "kNFLhugOP1e18pWvMWcdhNfeMjZ2": {
      "email": "fernandesryan1626@gmail.com",
      "profile": "https://lh3.googleusercontent.com/a-/AFdZucqGchXowFwL77eSywfbyeOQbCsotcfoMr9f4cN2Kw=s96-c",
      "search": "ryan fernandes",
      "uid": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "username": "Ryan Fernandes"
    },
    "lQxgXgOxmHdiDDpjmdZowTzX0qA2": {
      "email": "fernandesebastian@yahoo.com",
      "profile": "https://lh3.googleusercontent.com/a/AItbvmlIkNndyRu4z5X0NTHasNqglbNo8FOTUCrSegn1=s96-c",
      "search": "seby fernandes",
      "uid": "lQxgXgOxmHdiDDpjmdZowTzX0qA2",
      "username": "Seby fernandes"
    },
    "rSWf85R1yxNqe49isLO1E2sJjmt1": {
      "email": "gcs006.ryan.fernandes@gnkhalsa.edu.in",
      "profile": "https://lh3.googleusercontent.com/a-/AFdZucqYM3lsrdxQcfnqef-q_tL6j2643EPnX0OxGrcd=s96-c",
      "search": "ryan fernandes",
      "uid": "rSWf85R1yxNqe49isLO1E2sJjmt1",
      "username": "RYAN FERNANDES"
    }
  },
  "Videos": {
    "-NB13j1vAHj6-bTgYF1x": {
      "date": "Sep 3, 2022",
      "playlist": "123",
      "publisher": "kNFLhugOP1e18pWvMWcdhNfeMjZ2",
      "video_description": "Dance",
      "video_tags": "[dance]",
      "video_title": "The best ever",
      "video_url": "https://firebasestorage.googleapis.com/v0/b/stdio9-501d8.appspot.com/o/Videos%2FkNFLhugOP1e18pWvMWcdhNfeMjZ2%2F1662187073009%2Cmp4?alt=media&token=55cd9f0d-d54b-41bd-bc74-5518b2f89828",
      "videoid": "-NB13j1vAHj6-bTgYF1x"
    }
  }
}

My ContentModel java file

package com.example.stdio9.Models;

public class ContentModel {
    String id,publisher,playlist,type,video,video_description,video_url,video_tags,views,video_title,date;

    public ContentModel(String id, String publisher, String playlist, String type, String video, String video_description, String video_url, String video_tags, String views, String video_title, String date) {
        this.id = id;
        this.publisher = publisher;
        this.playlist = playlist;
        this.type = type;
        this.video = video;
        this.video_description = video_description;
        this.video_url = video_url;
        this.video_tags = video_tags;
        this.views = views;
        this.video_title = video_title;
        this.date = date;
    }

    public ContentModel() {}

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getPublisher() {
        return publisher;
    }

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

    public String getPlaylist() {
        return playlist;
    }

    public void setPlaylist(String playlist) {
        this.playlist = playlist;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getVideo() {
        return video;
    }

    public void setVideo(String video) {
        this.video = video;
    }

    public String getVideo_description() {
        return video_description;
    }

    public void setVideo_description(String video_description) {
        this.video_description = video_description;
    }

    public String getVideo_url() {
        return video_url;
    }

    public void setVideo_url(String video_url) {
        this.video_url = video_url;
    }

    public String getVideo_tags() {
        return video_tags;
    }

    public void setVideo_tags(String video_tags) {
        this.video_tags = video_tags;
    }

    public String getViews() {
        return views;
    }

    public void setViews(String views) {
        this.views = views;
    }

    public String getVideo_title() {
        return video_title;
    }

    public void setVideo_title(String video_title) {
        this.video_title = video_title;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

Answer 1

While it's hard to be certain without seeing the JSON at Content in your database, my guess is that you have a single item with its properties in the database. If that's the case, you shouldn't be looping over snapshot.getChildren() but do:

reference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot snapshot) {
        if(snapshot.exists()){
            list.clear();

            ContentModel model = snapshot.getValue(ContentModel.class);
            list.add(model);

            Collections.shuffle(list);

            adapter = new ContentAdapter(getActivity(),list);
            recyclerView.setAdapter(adapter);
            adapter.notifyDataSetChanged();
        }else{
            Toast.makeText(getActivity(), "No data found", Toast.LENGTH_SHORT).show();
        }
    }