Question

I’m using the SQLiteOpenHelper (shown below) in all my apps quiet happily. Lots of upgrades to existing databases ended successful in many year.

This time I need to upgrade the database in one of my apps and this step will last for some time. So I need to put these upgrade statements in their own thread.

What’s the best place to do so?

Any help is highly appreciated.

public class MySQLiteOpenHelper extends SQLiteOpenHelper {

    protected static final Object lock = new Object();

    private static final int DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 3;

    private Context context;
    private SQLiteDatabase database;

    public MySQLiteOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);

        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase database) {
        synchronized (lock) {
            this.database = database;

            // Create database statements
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {
        synchronized (lock) {
            this.database = database;

            switch (newVersion) {
                case DATABASE_VERSION:
                    switch (oldVersion) {
                        case 1:
                            upgradeFrom1To2();
                        case 2:
                            upgradeFrom2To3();
                    }

                    break;
            }
        }
    }

    private void upgradeFrom1To2() {
        // Upgrade database statements
    }

    private void upgradeFrom2To3() {
        // Upgrade database statements
    }
}

Answer 1

I’d put the code in an IntentService, which is an easy way to implement a background thread for a long-running operation, especially one that is saving data. Use broadcast Intent to send status from the IntentService to other components, and BroadcastReceiver to receive these Intent, if you need to.

I would really avoid doing this in AsyncTask within an Activity; there’s too much risk that the operation would be killed. Anyway, AsyncTask is much more complicated than IntentService.

One note: IntentService doesn’t persist anything, including its class fields. To protect yourself, you may want to store state in SharedPreferences.