Question

I am using a contentprovider, and 3 variables on the shared prefs, I’m wondering how to best ‘log the user out’..

I would expect it to truncate the db, and clear/delete shared prefs variables..

Currently I am clearing the shared prefs, and deleting the database, then taking the user back to the login screen.

SharedPreferences app_preferences = PreferenceManager
        .getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = app_preferences.edit();

// wipe user specific data
editor.remove("authenticated_user_id");
editor.remove("api_key");
editor.remove("last_sync_updates");

editor.commit();

// TODO possibly truncate rather than delete
// the apps database
getApplicationContext().deleteDatabase(
        DatabaseConstants.DATABASE_NAME);

// send the user to the login screen
Intent logoutIntent = new Intent(this, SplashActivity.class);
startActivity(logoutIntent);

But it doesn’t seem to clear the database, and I get database access errors randomly on the first transaction after logging out..

How is this typically done?

Answer 1

The Google I/O 2012 application does something similar so you might want to check that out. When the user logs out, the following call to the ContentResolver is made:

getContentResolver().delete(ScheduleContract.BASE_CONTENT_URI, null, null);

This calls the ScheduleProvider‘s delete method:

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
    if (uri == ScheduleContract.BASE_CONTENT_URI) {
        // Handle whole database deletes (e.g. when signing out)
        deleteDatabase();
        getContext().getContentResolver().notifyChange(uri, null, false);
        return 1;
    }

    /* ... */
}

where deleteDatabase() is the following private helper method:

private void deleteDatabase() {
    mOpenHelper.close();
    Context context = getContext();
    context.deleteDatabase(ScheduleContract.DATABASE_NAME);
    mOpenHelper = new ScheduleDatabase(context);
}

You can see the exact sequence of events that occurs beginning in ScheduleProvider.java.