java.lang.RuntimeException: Cannot create an instance of class com.example.architectureexample.NoteViewModel

Question

I am learning to use Room persistence library but stuck on a Runtime Exception

2020-03-12 00:47:18.087 2295-2295/com.example.architectureexample E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.architectureexample, PID: 2295
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.architectureexample/com.example.architectureexample.MainActivity}: java.lang.RuntimeException: Cannot create an instance of class com.example.architectureexample.NoteViewModel
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2723)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:163)
    at android.app.ActivityThread.main(ActivityThread.java:6238)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
 Caused by: java.lang.RuntimeException: Cannot create an instance of class com.example.architectureexample.NoteViewModel
    at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:275)
    at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
    at com.example.architectureexample.MainActivity.onCreate(MainActivity.java:22)
    at android.app.Activity.performCreate(Activity.java:6868)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2676)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784) 
    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:163) 
    at android.app.ActivityThread.main(ActivityThread.java:6238) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) 
 Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Constructor.newInstance0(Native Method)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:430)
    at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
    at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106) 
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185) 
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150) 
    at com.example.architectureexample.MainActivity.onCreate(MainActivity.java:22) 
    at android.app.Activity.performCreate(Activity.java:6868) 
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2676) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784) 
    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:163) 
    at android.app.ActivityThread.main(ActivityThread.java:6238) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) 
 Caused by: java.lang.RuntimeException: cannot find implementation for com.example.architectureexample.NoteDatabase. NoteDatabase_Impl does not exist
    at androidx.room.Room.getGeneratedImplementation(Room.java:94)
    at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:952)
    at com.example.architectureexample.NoteDatabase.getInstance(NoteDatabase.java:26)
    at com.example.architectureexample.NoteRepository.<init>(NoteRepository.java:16)
    at com.example.architectureexample.NoteViewModel.<init>(NoteViewModel.java:17)
    at java.lang.reflect.Constructor.newInstance0(Native Method) 
    at java.lang.reflect.Constructor.newInstance(Constructor.java:430) 
    at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267) 
    at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106) 
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185) 
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150) 
    at com.example.architectureexample.MainActivity.onCreate(MainActivity.java:22) 
    at android.app.Activity.performCreate(Activity.java:6868) 
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2676) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784) 
    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:163) 
    at android.app.ActivityThread.main(ActivityThread.java:6238) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) 

It is similar to this question. I tried implementing all the fixes mentioned in the above post. However, I am unable to solve this issue.

Here's my code:

Note

package com.example.architectureexample;

import androidx.room.Entity;
import androidx.room.PrimaryKey;

@Entity(tableName = "note_table")
public class Note {

    @PrimaryKey(autoGenerate = true)
    private int id;
    private String title;
    private String desc;
    private int priority;

    public Note(String title, String desc, int priority) {
        this.title = title;
        this.desc = desc;
        this.priority = priority;
    }

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

    public int getId() {
        return id;
    }

    public String getTitle() {
        return title;
    }

    public String getDesc() {
        return desc;
    }

    public int getPriority() {
        return priority;
    }
}

NoteDao

package com.example.architectureexample;

import androidx.lifecycle.LiveData;
import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;

import java.util.List;

@Dao
public interface NoteDao {

    @Insert
    void insert(Note note);

    @Update
    void update(Note note);

    @Delete
    void delete(Note note);

    @Query("DELETE FROM note_table")
    void deleteAllNotes();

    @Query("SELECT * FROM note_table")
    LiveData<List<Note>> getAllNotes();
}

NoteDatabase

import android.content.Context;
import android.os.AsyncTask;

import androidx.annotation.NonNull;
import androidx.room.Room;
import androidx.room.RoomDatabase;
import androidx.sqlite.db.SupportSQLiteDatabase;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public abstract class NoteDatabase extends RoomDatabase {

    private static NoteDatabase instance;
    public abstract NoteDao noteDao();
    private static final int NUMBER_OF_THREADS = 4;
    static final ExecutorService databaseWriteExecutor = Executors.newFixedThreadPool(NUMBER_OF_THREADS);

    public static synchronized NoteDatabase getInstance(Context context){
        if (instance == null){
            instance = Room.databaseBuilder(context.getApplicationContext(), NoteDatabase.class, "note_database")
                    .fallbackToDestructiveMigration()
                    .addCallback(callback)
                    .build();
        }
        return instance;
    }

    private static RoomDatabase.Callback callback = new RoomDatabase.Callback(){
        @Override
        public void onOpen(@NonNull SupportSQLiteDatabase db) {
            super.onCreate(db);
//            new PopulateDbAsyncTask(instance).execute();
            databaseWriteExecutor.execute(new Runnable() {
                @Override
                public void run() {
                    NoteDao noteDao = instance.noteDao();
                    noteDao.insert(new Note("Title 1", "Description 1", 1));
                    noteDao.insert(new Note("Title 2", "Description 2", 2));
                    noteDao.insert(new Note("Title 3", "Description 3", 3));
                }
            });
        }
    };

    private static class PopulateDbAsyncTask extends AsyncTask<Void, Void, Void>{
        private NoteDao noteDao;

        private PopulateDbAsyncTask(NoteDatabase db){
            noteDao = db.noteDao();
        }

        @Override
        protected Void doInBackground(Void... voids) {
            noteDao.insert(new Note("Title 1", "Description 1", 1));
            noteDao.insert(new Note("Title 2", "Description 2", 2));
            noteDao.insert(new Note("Title 3", "Description 3", 3));
            return null;
        }
    }
}

NoteRepository

import android.app.Application;
import android.os.AsyncTask;

import androidx.lifecycle.LiveData;
import androidx.room.Delete;

import java.util.List;

public class NoteRepository {
    private NoteDao noteDao;
    private LiveData<List<Note>> allNotes;

    public NoteRepository(Application application){
        NoteDatabase noteDatabase = NoteDatabase.getInstance(application);
        noteDao = noteDatabase.noteDao();
        allNotes = noteDao.getAllNotes();
    }

    public void insert(Note note){
        new InsertAsyncTask(noteDao).execute(note);
    }

    public void update(Note note){
        new UpdateAsyncTask(noteDao).execute(note);
    }

    public void delete(Note note){
        new DeleteAsyncTask(noteDao).execute(note);
    }

    public void deleteAllNotes(){
        new DeleteAllNotesAsyncTask(noteDao).execute();
    }

    public LiveData<List<Note>> getAllNotes(){
        return allNotes;
    }

    private static class InsertAsyncTask extends AsyncTask<Note, Void, Void>{
        private NoteDao noteDao;

        private InsertAsyncTask(NoteDao noteDao){
            this.noteDao = noteDao;
        }

        @Override
        protected Void doInBackground(Note... notes) {
            noteDao.insert(notes[0]);
            return null;
        }
    }

    private static class UpdateAsyncTask extends AsyncTask<Note, Void, Void>{
        private NoteDao noteDao;

        private UpdateAsyncTask(NoteDao noteDao){
            this.noteDao = noteDao;
        }

        @Override
        protected Void doInBackground(Note... notes) {
            noteDao.update(notes[0]);
            return null;
        }
    }

    private static class DeleteAsyncTask extends AsyncTask<Note, Void, Void>{
        private NoteDao noteDao;

        private DeleteAsyncTask(NoteDao noteDao){
            this.noteDao = noteDao;
        }

        @Override
        protected Void doInBackground(Note... notes) {
            noteDao.delete(notes[0]);
            return null;
        }
    }

    private static class DeleteAllNotesAsyncTask extends AsyncTask<Void, Void, Void>{
        private NoteDao noteDao;

        private DeleteAllNotesAsyncTask(NoteDao noteDao){
            this.noteDao = noteDao;
        }

        @Override
        protected Void doInBackground(Void... voids) {
            noteDao.deleteAllNotes();
            return null;
        }
    }
}

NoteViewModel

package com.example.architectureexample;

import android.app.Application;

import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;

import java.util.List;

public class NoteViewModel extends AndroidViewModel {
    private NoteRepository repository;
    private LiveData<List<Note>> allNotes;

    public NoteViewModel(@NonNull Application application) {
        super(application);
        repository = new NoteRepository(application);
        allNotes = repository.getAllNotes();
    }

    public void insert(Note note){
        repository.insert(note);
    }

    public void update(Note note){
        repository.update(note);
    }

    public void delete(Note note){
        repository.delete(note);
    }

    public void deleteAllNotes(){
        repository.deleteAllNotes();
    }

    public LiveData<List<Note>> getAllNotes(){
        return allNotes;
    }
}

MainActivity

package com.example.architectureexample;

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;

import android.os.Bundle;
import android.widget.Toast;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private NoteViewModel noteViewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        noteViewModel = new ViewModelProvider(this).get(NoteViewModel.class);
        noteViewModel.getAllNotes().observe(this, new Observer<List<Note>>() {
            @Override
            public void onChanged(List<Note> notes) {
                Toast.makeText(MainActivity.this, "Test Toast", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

Any help would be appreciated.

Thanks, in advance.