June 2011
Intermediate to advanced
590 pages
19h 31m
English
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20Touch Events and UIResponder
In your Hypnosister project from 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 20.1). 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 20.1 A drawing program
Touch Events
As a subclass of UIResponder, your view can override four methods to handle the four ...
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