Specialized Layers - iOS Core Animation - page 141

Figure 6.15 A single triangle rendered in a CAEAGLLayer using OpenGL
In a real OpenGL application, we would probably want to call the -drawFrame method
60 times per second using an NSTimer or CADisplayLink (see Chapter 11, “Timer-
Based Animation”), and we would separate out geometry generation from drawing so that
we aren't regenerating our triangle's vertices every frame (and also so that we can draw
something other than a single triangle), but this should be enough to demonstrate the
principle.
AVPlayerLayer
The last layer type we will look at is AVPlayerLayer . Although not part of the Core
Animation framework (the AV prefix is a bit of a giveaway), AVPlayerLayer is an
example of another framework (in this case, AVFoundation) tightly integrating with Core
Animation by providing a CALayer subclass to display a custom content type.
AVPlayerLayer is used for playing video on iOS. It is the underlying implementation
used by high-level APIs such as MPMoviePlayer , and provides lower-level control over
the display of video. Usage of AVPlayerLayer is actually pretty straightforward: You
can either create a layer with a video player already attached using the
+playerLayerWithPlayer: method, or you can create the layer first and attach an
AVPlayer instance using the player property.
Before we begin, we need to add the AVFoundation framework to our project, because it's
not included in the default project template. After you've done that, see Listing 6.15 for the
code to create a simple movie player. Figure 6.16 shows the movie player in action.