Room Dao Cannot Resolve This Symbol (Table_Name) Android Java

Question

When I made a method that select all the items from a table name the Dao class could not resolve the table name!!

I could not understand why this happened at all. The problem is that I had another project that I was working on (two days ago!!) in which I used Room as well and it was working perfectly, and when I made this new project and defined the classes shown below the old project has the same problem now! (lol)

my object class

package com.example.adapterapp.Entites;

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

@Entity(tableName = "items_table")
public class RoomItem {

    @PrimaryKey(autoGenerate = true)
    private int itemId;

    private final String itemTitle;

    private final String itemSubtitle;

    private final String imageUri;

    public RoomItem(String itemTitle, String itemSubtitle, String imageUri) {
        this.itemTitle = itemTitle;
        this.itemSubtitle = itemSubtitle;
        this.imageUri = imageUri;
    }

    public int getItemId() {
        return itemId;
    }

    public String getItemTitle() {
        return itemTitle;
    }

    public String getItemSubtitle() {
        return itemSubtitle;
    }

    public String getImageUri() {
        return imageUri;
    }


}

dao

package com.example.adapterapp.RoomDatabase;

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 com.example.adapterapp.Entites.RoomItem;

import java.util.List;

@Dao
public interface ItemDao {

    @Insert
    void insertItem(RoomItem roomItem);

    @Update
    void updateItem(RoomItem roomItem);

    @Delete
    void deleteItem(RoomItem roomItem);

    @Query("SELECT * FROM items_table")
    LiveData<List<RoomItem>> getAllItems();

}

database

package com.example.adapterapp.RoomDatabase;

import android.content.Context;

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

import com.example.adapterapp.Entites.RoomItem;

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

@Database(entities = RoomItem.class, version = 1)
public abstract class ItemDatabase extends RoomDatabase {

    private static ItemDatabase instance;

    public abstract ItemDao noteDao();

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

    private static final RoomDatabase.Callback roomCallback = new RoomDatabase.Callback() {
        @Override
        public void onCreate(@NonNull SupportSQLiteDatabase db) {
            super.onCreate(db);
            new PopulateTaskRunner().executeAsync(new PopulateDatabaseTask(instance));
        }
    };

    private static class PopulateTaskRunner {
        private final Executor executor = Executors.newSingleThreadExecutor(); // change according to your requirements

        private void executeAsync(PopulateDatabaseTask populateDatabaseTask) {
            executor.execute(() -> {
                try {
                    populateDatabaseTask.itemDao.insertItem(new RoomItem("title: 1", "subtitle: 1", null));
                    populateDatabaseTask.itemDao.insertItem(new RoomItem("title: 2", "subtitle: 2", null));
                    populateDatabaseTask.itemDao.insertItem(new RoomItem("title: 3", "subtitle: 3", null));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
    }

    private static class PopulateDatabaseTask {

        private final ItemDao itemDao;

        private PopulateDatabaseTask(ItemDatabase itemDatabase) {
            this.itemDao = itemDatabase.noteDao();
        }
    }

}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.4.2'
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    //lifecycle
    def lifecycle_version = "2.6.0-alpha01"
    implementation "androidx.lifecycle:lifecycle-viewmodel:2.5.0"
    implementation "androidx.lifecycle:lifecycle-livedata:2.5.0"
    implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"

    //room database
    def room_version = "2.4.2"
    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:2.4.2"

    //firebase
    // Import the BoM for the Firebase platform
    // When using the BoM, you don't specify versions in Firebase library dependencies
    implementation platform('com.google.firebase:firebase-bom:30.2.0')
    //implementation 'com.google.firebase:firebase-analytics'
    implementation 'com.google.firebase:firebase-firestore'
    implementation 'com.google.firebase:firebase-storage'
    implementation 'com.google.firebase:firebase-messaging'
    implementation 'com.google.firebase:firebase-auth'
}

Answer 1

I had the same problem recently and found out that I just forgot to put this {}

Change

@Database(entities = RoomItem.class, version = 1)

To

@Database(entities = {RoomItem.class}, version = 1)