mx.states.AddChild (Flex 3.4)

Package	mx.states
Class	public class AddChild
Inheritance	AddChild Object
Implements	IOverride

The AddChild class adds a child display object, such as a component, to a container as part of a view state. You use this class in the overrides property of the State class. Use the creationPolicy property to specify to create the child at application startup or when you change to a view state.

The child does not dispatch the creationComplete event until it is added to a container. For example, the following code adds a Button control as part of a view state change:

  <mx:AddChild relativeTo="{v1}">
      <mx:Button id="b0" label="New Button"/>
  </mx:AddChild>

In the previous example, the Button control does not dispatch the creationComplete event until you change state and the Button control is added to a container. If the AddChild class defines both the Button and a container, such as a Canvas container, then the Button control dispatches the creationComplete event when it is created. For example, if the creationPolicy property is set to all, the Button control dispatches the event at application startup. If the creationPolicy property is set to auto, the Button control dispatches the event when you change to the view state.

MXML Syntax expanded

Hide MXML Syntax

The <mx:AddChild> tag has the following attributes:

  <mx:AddChild
  Properties
  target="null"
  targetFactory="null"
  creationPolicy="auto"
  position="lastChild"
  relativeTo="parent of the State object"
  />

Default MXML PropertytargetFactory

View the examples

	Property	Defined By
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		creationPolicy : String The creation policy for this child.	AddChild
		position : String The position of the child in the display list, relative to the object specified by the relativeTo property.	AddChild
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object
		relativeTo : UIComponent The object relative to which the child is added.	AddChild
		target : DisplayObject The child to be added.	AddChild
		targetFactory : IDeferredInstance The factory that creates the child.	AddChild

	Method	Defined By
		AddChild(relativeTo:UIComponent = null, target:DisplayObject = null, position:String = "lastChild") Constructor.	AddChild
		apply(parent:UIComponent):void Applies the override.	AddChild
		createInstance():void Creates the child instance from the factory.	AddChild
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		initialize():void Initializes the override.	AddChild
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		remove(parent:UIComponent):void Removes the override.	AddChild
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toString():String Returns the string representation of the specified object.	Object
		valueOf():Object Returns the primitive value of the specified object.	Object

Property Detail

creationPolicy

property

creationPolicy:String

The creation policy for this child. This property determines when the targetFactory will create the instance of the child. Flex uses this properthy only if you specify a targetFactory property. The following values are valid:

Value	Meaning
`auto`	(default)Create the instance the first time it is needed.
`all`	Create the instance when the application started up.
`none`	Do not automatically create the instance. You must call the `createInstance()` method to create the instance.

The default value is "auto".

Implementation
public function get creationPolicy():String
public function set creationPolicy(value:String):void

position

property

public var position:String

The position of the child in the display list, relative to the object specified by the relativeTo property. Valid values are "before", "after", "firstChild", and "lastChild".

The default value is "lastChild".

relativeTo

property

public var relativeTo:UIComponent

The object relative to which the child is added. This property is used in conjunction with the position property. This property is optional; if you omit it, Flex uses the immediate parent of the State object, that is, the component that has the states property, or <mx:states>tag that specifies the State object.

target

property

target:DisplayObject

The child to be added. If you set this property, the child instance is created at app startup. Setting this property is equivalent to setting a targetFactory property with a creationPolicy of "all".

Do not set this property if you set the targetFactory property.

Implementation
public function get target():DisplayObject
public function set target(value:DisplayObject):void

targetFactory

property

targetFactory:IDeferredInstance

The factory that creates the child. You can specify either of the following items:

A factory class that implements the IDeferredInstance interface and creates the child instance or instances.
A Flex component, (that is, any class that is a subclass of the UIComponent class), such as the Button contol. If you use a Flex component, the Flex compiler automatically wraps the component in a factory class.

If you set this property, the child is instantiated at the time determined by the creationPolicy property.

Do not set this property if you set the target property. This propety is the AddChild class default property. Setting this property with a creationPolicy of "all" is equivalent to setting a target property.

Implementation
public function get targetFactory():IDeferredInstance
public function set targetFactory(value:IDeferredInstance):void

Constructor Detail

AddChild

()

Constructor

public function AddChild(relativeTo:UIComponent = null, target:DisplayObject = null, position:String = "lastChild")

Constructor.

Parameters

	`relativeTo:UIComponent` (default = `null`) — The component relative to which child is added.

	`target:DisplayObject` (default = `null`) — The child object. All Flex components are subclasses of the DisplayObject class.

	`position:String` (default = "`lastChild`") — the location in the display list of the `target` relative to the `relativeTo` component. Must be one of the following: "firstChild", "lastChild", "before" or "after".

Method Detail

apply

()

method

public function apply(parent:UIComponent):void

Applies the override. Flex retains the original value, so that it can restore the value later in the remove() method.

This method is called automatically when the state is entered. It should not be called directly.

Parameters

parent:UIComponent — The parent of the state object containing this override. The override should use this as its target if an explicit target was not specified.

createInstance

()

method

public function createInstance():void

Creates the child instance from the factory. You must use this method only if you specify a targetFactory property and a creationPolicy value of "none". Flex automatically calls this method if the creationPolicy property value is "auto" or "all". If you call this method multiple times, the child instance is created only on the first call.

initialize

()

method

public function initialize():void

Initializes the override. Flex calls this method before the first call to the apply() method, so you put one-time initialization code for the override in this method.

Flex calls this method automatically when the state is entered. It should not be called directly.

remove

()

method

public function remove(parent:UIComponent):void

Removes the override. The value remembered in the apply() method is restored.

This method is called automatically when the state is entered. It should not be called directly.

Parameters

parent:UIComponent — The parent of the state object containing this override. The override should use this as its target if an explicit target was not specified.

Examples How to use this example

StatesExample.mxml

<?xml version="1.0" ?>
<!-- Simple example to demonstrate the States class. -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">

    <!-- Define one view state, in addition to the base state.-->
    <mx:states>
        <mx:State name="Register">
            <mx:AddChild relativeTo="{loginForm}" position="lastChild">
                <mx:target>
                    <mx:FormItem id="confirm" label="Confirm:">
                        <mx:TextInput/>
                    </mx:FormItem>
                </mx:target>
            </mx:AddChild>
            <mx:SetProperty target="{loginPanel}" name="title" value="Register"/>
            <mx:SetProperty target="{loginButton}" name="label" value="Register"/>
            <mx:SetStyle target="{loginButton}" 
                name="color" value="blue"/>
            <mx:RemoveChild target="{registerLink}"/>
            <mx:AddChild relativeTo="{spacer1}" position="before">
                <mx:target>
                    <mx:LinkButton id="loginLink" label="Return to Login" click="currentState=''"/>
                </mx:target>
            </mx:AddChild>
        </mx:State>
    </mx:states>

    <!-- Define a Panel container that defines the login form.-->
    <mx:Panel title="Login" id="loginPanel" 
        horizontalScrollPolicy="off" verticalScrollPolicy="off"
        paddingTop="10" paddingLeft="10" paddingRight="10" paddingBottom="10">

        <mx:Text width="100%" color="blue"
            text="Click the 'Need to Register?' link to change state. Click the 'Return to Login' link to return to the base state."/>

        <mx:Form id="loginForm" >
            <mx:FormItem label="Username:">
                <mx:TextInput/>
            </mx:FormItem>
            <mx:FormItem label="Password:">
                <mx:TextInput/>
            </mx:FormItem>
        </mx:Form>
        <mx:ControlBar>
            <mx:LinkButton id="registerLink"  label="Need to Register?"
                click="currentState='Register'"/>
            <mx:Spacer width="100%" id="spacer1"/>
            <mx:Button label="Login" id="loginButton"/>
        </mx:ControlBar>
    </mx:Panel>
</mx:Application>

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