Scrolling uiTextField for different keyboard sizes

Question

I have a UITableView with a number of UITextFields. When the user edits the textfields, the textfield that is the firstresponder is scrolled to the position just above the keyboard. This works fine for textfields that use the default keyboard. But I have one textfield that is using a UIPickerView as inputView. Because I want the user to confrm the selection in the pickerview I also added a accessoryview with a done-button to the inputAccessoryView of the textfield.

Now I encounter a behaviour that I don't understand. When there is no keyboard shown and I click the textfield with the pickerview, I receive the notification for UIKeyboardDidShowNotification. The notification leads the the following function call:

- (void)keyboardWasShown:(NSNotification *)aNotification {
    NSDictionary* info = [aNotification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;

    // handle resize of tableview frame...
}

The height of the keyboard (kbSize.height) is 260. This is equal to the default keyboard size of 216 + 44 for the toolbar in the accessoryview. The textfield is scrolled to a position above the toolbar in the accessoryview.

The strange behaviour happens when i first click a textfield with a default keyboard and than continue (without dismissing the keyboard) with the textfield with the pickerview. The pickerview is shown as expected, but the keyboard size does not change and stays 216 (notification is handled). This lead to different scroll behaviour: the textfield is visible behind the translucent toolbar in the accessoryview.

Please, can someone explain why the keyboard size is different for the pickerview in both cases.

Please, can someone tell me how to handle this in code. It is fine for me when the textfield is scrolled to the position behind the translucent toolbar.