Question

I’m curious about the automatic scrolling in the Notepad app when I start editing text that would otherwise be obscured by the keyboard. I understand what is happening in general: the app uses the cursor’s position, the keyboard height and some offset to scroll the notepad. However I’m unclear about exactly what objects/values are changing.

What is happening in regards to frames, bounds contentOffsets etc?

Edit: I’m interested in how this automatic scrolling works in general. Notepad app is just a good example.

Answer 1

This is described in Text, Web, and Editing Programming Guide for iOS:

When asked to display the keyboard, the system slides it in from the bottom of the screen and positions it over your application’s content. Because it is placed on top of your content, it is possible for the keyboard to be placed on top of the text object that the user wanted to edit. When this happens, you must adjust your content so that the target object remains visible.

Adjusting your content typically involves temporarily resizing one or more views and positioning them so that the text object remains visible. The simplest way to manage text objects with the keyboard is to embed them inside a UIScrollView object (or one of its subclasses like UITableView). When the keyboard is displayed, all you have to do is reset the content area of the scroll view and scroll the desired text object into position. Thus, in response to a UIKeyboardDidShowNotification, your handler method would do the following:

1. Get the size of the keyboard.
2. Adjust the bottom content inset of your scroll view by the keyboard height.
3. Scroll the target text field into view.