Cover by Joe Conway, Aaron Hillegass

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19Touch Events and UIResponder

In Chapter 6, you created a UIScrollView that handled touch events to scroll a view and even handled a multi-touch event to zoom. The UIScrollView class makes scrolling and zooming easy to implement. But what if you want to do something else, something special or unique, with touch events?

In this chapter, you are going to create a view that lets the user draw lines by dragging across the view (Figure 19.1). Using multi-touch, the user will be able to draw more than one line at a time. Double-tapping will clear the screen and allow the user to begin again.

Figure 19.1  A drawing program

A drawing program

Touch Events

As a subclass ...

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