Graphics Programs Reference
In-Depth Information
Animation Objects
While you have not yet used animations objects explicitly, all animation in iOS is driven by
them, including the animations you saw in the last chapter. The abstract superclass for all
animation objects is
CAAnimation
.
CAAnimation
is responsible for handling timing;
for instance, it has a
duration
property that specifies the length of the animation. As an
abstract superclass, you do not use
CAAnimation
objects directly. Instead, you use one
of its concrete subclasses shown in
Figure 23.1
.
Figure 23.1 Inheritance
CAPropertyAnimation
is a subclass of
CAAnimation
that extends the ability of its
superclass by adding the ability to change the properties of a layer. Each property anima-
tion has a
key path
of type
NSString
. This string is the name of an animatable property
of a
CALayer
. Many of
CALayer
's properties are animatable. Check the documentation
for a list. Search for “animatable properties” and look under the Core Animation Program-
ming Guide (
Figure 23.2
).
Figure 23.2 Animatable properties in the documentation
