12 Touch Events and UIResponder
For the next three chapters, you are going to step away from Homepwner and build a new application named TouchTracker to learn more about touch events and gestures, as well as debugging applications.
In this chapter, you will create a view that lets the user draw lines by dragging across the view (Figure 12.1). Using multi-touch, the user will be able to draw more than one line at a time.
Figure 12.1 A drawing program
As a subclass of UIResponder, a UIView can override four methods to handle the four distinct touch events:
a finger or fingers touches the screen ...