Question

Exception:

CREATE TABLE android_metadata failed
Failed to setLocale() when constructing, closing the database
android.database.sqlite.SQLiteException: database is locked

My app works fine and has no db issues, except when onUpgrade() is called.

When onUpgrade is automatically called, it tries to use the CarManager class below to do data manipulation required for the upgrade. This fails because the db is locked.

Because this seems like it should be a normal thing to do, it seems that I must not be structuring the following code correctly (two classes follow, a helper and a table manager):

public class DbHelper extends SQLiteOpenHelper {

    private Context context;

    //Required constructor
    public DbAdapter(Context context)
    {
        super(context, "my_db_name", null, NEWER_DB_VERSION);
        this.context = context;
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
    {
        overrideDB = db;
        CarManager.migrateDataForOnUpgrade(context);
    }
}


public class CarManager {

    DbHelper dbHelper;

    public CarManager(Context context)
    {
        dbHelper = new DbHelper(context);
    }

    public void addCar(String make, String model)
    {
        ContentValues contentValues = new ContentValues();
        contentValues.put("make", make);
        contentValues.put("model", model);

        SQLiteDatabase db = dbHelper.getWritableDatabase();
        db.insert("car", null, contentValues);
        db.close();
    }

    public static void migrateDataForOnUpgrade()
    {
        //Code here that migrates data when onUpgrade() is called
        //Db lock happens here
    }
}

Any ideas?
Do people set up table manager (ex: dao) differently than this?

edit: I talked to the google team @ android developer hours, and they said onUpgrade3 was never meant to do anything like structural changes (alters). So yes, it seems like there are some hacks that must be used in many instances right now.

Answer 1

I use the following model by extending the Application class. I maintain a single static instance of my db helper which all other app components use…

public class MyApp extends Application {

    protected static MyAppHelper appHelper = null;
    protected static MyDbHelper dbHelper = null;

    @Override
    protected void onCreate() {
        super.onCreate();
        ...
        appHelper = new MyAppHelper(this);
        dbHelper = MyAppHelper.createDbHelper();
        dbHelper.getReadableDatabase(); // Trigger creation or upgrading of the database
        ...
    }
}

From then on any class which needs to use the db helper simply does the following…

if (MyApp.dbHelper == null)
    MyApp.appHelper.createDbHelper(...);
// Code here to use MyApp.dbHelper