What Can and Should I Animate? - Core Animation - page 17

LISTING 2-2 Animating the Background Color from Red to Green on iPhone

- ( CABasicAnimation *)backgroundColorAnimation;
{

CABasicAnimation *anim =
[ CABasicAnimation
animationWithKeyPath :@”backgroundColor” ];

[anim setDuration :5.0];

[anim setFromValue :( id )[[ UIColor redColor ] CGColor]];
[anim setToValue:( id )[[ UIColor greenColor ] CGColor]];

return anim;

}

Color fields that you can animate include

. backgroundColor

The layer's background color.

. borderColor

The color of the layer's border.

. shadowColor

The color of the layer's shadow. At the time of this writing, the shadowColor prop-
erty is not available on the iPhone.

Motion
When you want motion on the screen, Core Animation provides rectangles and points in
each layer that you can animate. Motion fields you can animate include

. anchorPoint

The default anchorPoint of a layer is 0.5,0.5 , which indicates the center of the
layer is the anchorPoint . If you change the anchorPoint to 0.0,0.0 , it will be
located at the bottom-left corner.

. bounds

The bounds property animates the shape of the bounding rectangle. It does not
affect the layer's position.

. frame

The frame property is not animated in a layer. You can set this parameter and the
layer's internal value with change; however, you won't see the actual animation. If
you want to animate a layer's bounds, that is, its bounding rectangle, use the bounds
property. If you want to change the position, use the position property. On views
and windows, setting frame causes the bounding frame to animate.