To delete a task, create a new AsyncTask in the MainActivity:

private class DeleteTaskAsyncTask(private val database: AppDatabase?, private val selectedTask: Task) : AsyncTask<Void, Void, Unit>() {

    override fun doInBackground(vararg params: Void): Unit? {
        return database?.taskDao()?.deleteTask(selectedTask)
    }
}

Next, in onOptionsItemSelected(), locate the following line of code:

dbHelper.deleteTask(selectedTask)

Replace it with this line of code:

DeleteTaskAsyncTask(database, selectedTask).execute()

Build and run. Select a task and click the Delete menu item. This removes the selected task from the ListView, removes it from the database as well, and displays a ticker with the message Task deleted successfully at the bottom of the screen:

That's it. As you can see, using the ORM lets you write less code and reduces SQL errors.