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();

Possible duplicate of [Query if Android database exists!](https://stackoverflow.com/questions/3386667/query-if-android-database-exists) — Hemant Parmar, Mar 13 '18 at 11:59
@HemantParmar . This is not a duplicate. Here I am using the android Room API not the SQLlite one — Abx, Mar 13 '18 at 12:09
Have you found a solution to this problem? How do you call an existing database? — loopidio, Jun 05 '18 at 08:00

score 3 · Answer 1 · answered Mar 13 '18 at 11:58

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();
}

score 3 · Accepted Answer · edited May 28 '23 at 12:52

When you create database, the database onCreate() callback get called when the application starts. you can use the 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"

score 1 · Answer 3 · answered Feb 14 '19 at 15:35

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
        }
    }

and do not forget: implementation "android.arch.persistence.room:runtime:1.1.1" kapt "android.arch.persistence.room:compiler:1.1.1" or you will have RoomDatabase_Impl does not exist — Vladimir Vartanyan, Feb 14 '19 at 15:43

score -1 · Answer 4 · answered Mar 13 '18 at 12:01

-1

Try this

if (!db.exists()) {
    // Database does not exist so copy it from assets here
    Log.i("Database", "Not Found");
} else {
    Log.i("Database", "Found");
}

answered Mar 13 '18 at 12:01

Gastón Saillén

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How to check if a DB exists in Android?

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