How to check if a DB exists in Android?

Question

I am using Room API to implement a DB in my Android app. It seems that every time I load my app it tries to create the database again and again. Is there any way to restrict this?

 db = Room.databaseBuilder(context, AppDatabase.class, "database-name").build();

Answer 1

when you create database it call when application start that time their db create.you used to below code in app activity and that activity call in manifest file in application class call like used below code ..

public class AppActivity extends Application {

AppDatabase db;

@Override
public void onCreate() {
    super.onCreate();
    db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "database-name").build();
}

public AppDatabase getDatabase() {
    return db;
}

} and add below line manifest file .. add below line in application tag

        android:name="AppActivity"

Answer 2

You are using db that is, in fact, a file. You can check, if it exists, this method could be helpful:

private static boolean doesDatabaseExist(Context context, String dbName) {
    File dbFile = context.getDatabasePath(dbName);
    return dbFile.exists();
}

Answer 3

You can get count of entities in db (TODO app - example). entities > 0.

class App: Application() {
    override fun onCreate() {
        super.onCreate()
        instance = this
        database = Room.databaseBuilder(applicationContext,
            AppDatabase::class.java, "database").build()
    }
    companion object {
        lateinit var instance: App
        lateinit var database: AppDatabase
    }
}

//DB class

 @Database(entities = [Task::class], version = 1, exportSchema = false)
       abstract class AppDatabase : RoomDatabase() {
       abstract fun taskDao(): TaskDao
}

//Dao interface

   @Dao
    interface TaskDao {
        @Query("SELECT COUNT(id) FROM tasks")
        fun getTasksCount(): Int
    }

//Model

@Entity(indices = [Index(value = ["title"], unique = true)], tableName ="tasks")
    class Task(
        var title: String = "",
        var description: String = "",
        var date: Date,
        @Embedded 
        var remind: Constants.RemindPeriod = Constants.RemindPeriod.MIN5,
        @Embedded
        var prior: Priority) : Serializable {
        @PrimaryKey(autoGenerate = true)
        var id: Long = 0}

//CheckDB

 private fun checkDatabaseState() {
        doAsync {
            val db = App.database
            val entityCount = db.taskDao().getTasksCount().or(0)
            isDatabaseNotEmpty = entityCount > 0
        }
    }