Macromedia flex 2 Manual

158

Creating Advanced Visual Components in ActionScript

// Call the createChildren() method of the superclass.
super.createChildren();

// Test for the existence of the children before creating them.
// This is optional, but do this so a subclass can create a different
// child.
if (!text_mc) {

text_mc = new TextArea();
text_mc.explicitWidth = 80;
text_mc.editable = false;
text_mc.addEventListener("change", handleChangeEvent);
// Add the child component to the custom component.
addChild(text_mc);

}

// Test for the existence of the children before creating them.
if (!mode_mc) {

mode_mc = new Button();
mode_mc.label = "Toggle Editing";
mode_mc.addEventListener("click", handleClickEvent);
// Add the child component to the custom component.
addChild(mode_mc);

}

}

Notice in this example that the 

createChildren()

 method calls the 

addChild()

 method to 

add the child component. You must call the 

addChild()

 method for each child object.

After you create a child component, you can use properties of the child component to define 
its characteristics. In this example, you create the Button and TextArea controls, initialize 
them, and register event listeners for them. You could also apply skins to the child 
components. For a complete example, see 

.

Implementing the commitProperties() method

You use the 

commitProperties()

 method to coordinate modifications to component 

properties. Most often, you use it with properties that affect how a component appears on the 
screen. 

Flex schedules a call to the 

commitProperties()

 method when a call to the 

invalidateProperties()

 method occurs. The 

commitProperties()

 method executes 

during the next 

render

 event after a call to the 

invalidateProperties()

 method. When 

you use the 

addChild()

 method to add a component to a container, Flex automatically calls 

the 

invalidateProperties()

 method.