MACROMEDIA FLEX - DEVELOPING COMPONENTS AND THEMES, Руководство пользователя

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54 Chapter 3: Creating Advanced Components in Flash MX 2004
Implementing the constructObject2() method
The
constructObject2()
method is effectively the constructor for your class. The
UIObject.constructObject2()
method calls the
init()
and
createChildren()
methods. It
should apply any properties in the initObj that are needed by
init()
and
createChildren()
,
and then call
super.constructObject2()
.
The
constructObject2()
method has the following signature:
constructObject2(initObj:Object):Void
In addition, if you use clip parameters, you should add a call to the
applyProperties()
method
at the end of the
constructObject2()
method; for example:
function constructObject2(o:Object):Void {
super.constructObject2(o);
applyProperties(o, Label.prototype.clipParameters);
}
If you override the
constructObject2()
method, you must at least call the
super.constructObject2()
method.
The initObj contains all the component instance’s properties that are set in the MXML tag
(and stored as clip parameters). Flex creates this object implicitly during instantiation of the
component.
Implementing the init() method
Flash calls the
init()
method when the class is created. At a minimum, the
init()
method
should call the superclass’s
init()
method. The
width
,
height
, and
clip
parameters are not
properly set until after this method is called.
function init(Void):Void {
super.init();
}
The implicit init object (initObj) contains everything passed in through the
initObj
argument to
the
createClassObject()
method. You can access it in the
init()
method.
Note: Do not create child objects in the
init()
method. You should use it only for setting up initial
properties.
Implementing the createChildren() method
Components implement the
createChildren()
method to create subobjects (such as other
components) in the component. Rather than calling the subobject’s constructor in the
createChildren()
method, call the
createClassObject()
method to instantiate a subobject
of your component.
The
createClassObject()
method has the following signature:
createClassObject( className , instanceName , depth , initObject )