[Flex] Life Cycle of flex component and container children

Detailed usage Flex When you encounter such a problem, New Come out Component Internal components cannot be operated directly. Null . Of course, we are writing Script You can set Children In Constructor . In this way, this problem will not occur. But when we are doing Mxml This problem is very obvious when components are used. We must follow Flex Of Component Life Cycle . The common practice is to put Property Inside , For example

<? XML version = "1.0" encoding = "UTF-8"?>

<Mx: canvas xmlns: MX = "http://www.adobe.com/2006/mxml" width = "400" Height = "300">

<Mx: SCRIPT>

<! [CDATA [

Private var title: string;

Private var bnamechanged: Boolean;

 

Public Function set title (value): void

{

If (title! = Value)

{

Title = value;

Bnamechanged = true;

This. invalidateproperties ();

}

}

Override protected function commitproperties (): void

{

Super. commitproperties ();

If (bnamechanged)

{

Bnamechanged = false;

Lblname. Text = title;

}

}

]>

</MX: SCRIPT>

<Mx: Label id = "lblname"/>

</MX: canvas>

 

However, you are usingContainerInNullBut what is the problem? For example, you put two components on oneTabnavigate.

 

<? XML version = "1.0" encoding = "UTF-8"?>

<Mx: Application xmlns: MX = "http://www.adobe.com/2006/mxml" layout = "absolute" xmlns: Local = "*">

<Mx: tabnavigator>

<Local: testcomponent id = "test1" Title = "Test 1"/>

<Local: testcomponent id = "Test2" Title = "Test 2"/>

</MX: tabnavigator>

</MX: Application>

Try to ensure 

Error #1009: the attribute or method referenced by the null object cannot be accessed.

At this time, I started to complain. Why?FlexWhy do you not comply with your game rules?,HereTabnavigatorOfChildrenIt is called before it is created,CommitepropertiesOrUpdatedisplaylistMethod. This should beFlexOneBug.

To solve this problem, we only needTabnavigatorIn the createChildrenAllChildrenAre created. At this time, we need to pay attentionContainer. createpolicyAttribute.ContainerInternalChildrenNot inCreatechildAs forChildrenThe creation time, take a good look

Containercreationpolicy,AndContainerInternalChildren (PassMxmlAddedChildren)AndCreatechildrenCreated inChidrenIt can be understood as different types.

In the above exampleTabnavigatorAddCreatepolicy = "all"All files are fixed.

 

If you have any questions, please correct them..