2.6. Assigning Characteristics to Your Dynamic Effects
You like the default physics built into the dynamic behaviors of UIKit, but you want to be able to assign different characteristics, such as mass and elasticity, to various items that you control using dynamic behaviors.
Instantiate an object of type
UIDynamicItemBehavior and assign your dynamic
items to it. Once instantiated, use the various properties of this class
to change the characteristics of your dynamic items. Then add this
behavior to your animator (see Recipe 2.0) and let the animator take care of the rest
Dynamic behaviors are great for adding real-life physics to items
that conform to the
protocol, such as all views of type
UIView. In some apps, though, you may wish to
explicitly specify the characteristics of a specific item. For instance,
in an app where you are using gravity and collision behaviors (see Recipe 2.1 and Recipe 2.2),
you may wish to specify that one of the items on your screen affected by
this gravity and the collision has to bounce harder than the other item
when it collides with a boundary. Another example is when you want to
specify that an item, during all the different dynamic animations that
will be applied to it with an animator, should not rotate at all.
These are all easily doable when you use instances of the
UIDynamicItemBehavior class. These
instances are dynamic behaviors too, and you can add them to an animator
addBehavior: instance ...