50.7 Adding a CustomAttribute to a Transition

The KeyAttribute property is limited to built-in effects such as resizing and rotation. Additional changes are also possible by declaring CustomAttributes. Unlike KeyAttributes, which are stored in the Transition element, CustomAttributes are located in the start and end constraint sets. As such, these attributes can only be declared to take effect at start and end points (in other words you cannot specify an attribute keyframe at a position partway through a transition timeline).

For this example, we will configure the button to gradually change color from red to green. Begin by selecting the start box marked A in Figure 50-18 followed by the myButton view constraint set (B):

Figure 50-18

Referring to the Attributes tool window, click on the + button in the CustomAttributes section as highlighted below:

Figure 50-19

In the resulting dialog (Figure 50-20) change the type of the attribute to Color and enter backgroundColor...