MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manual do Utilizador descarregar pdf (Página 106)

106 Binding

The <mx:Binding> tag must be a top-level

tag

In Flex 1.5, you could place the <mx:Binding> tag in a Flex container. In Flex 2.0, the

<mx:Binding> tag must be a top-level tag in the MXML file. For example:

Flex 1.x:

<mx:HBox>

<mx:Label id="myLabel"/>

<mx:Label id="my2ndLabel" text="hello"/>

<mx:Binding source="my2ndLabel.text" destination="myLabel.text"/>

</mx:HBox>

Flex 2:

<mx:Binding source="my2ndLabel.text" destination="myLabel.text"/>

<mx:HBox>

<mx:Label id="myLabel"/>

<mx:Label id="my2ndLabel" text="hello"/>

</mx:HBox>

Binding from a property

To make properties usable as the source for a data binding expression in Flex 2, you use the

[Bindable] metadata tag. Properties of custom components often have getter/setter pairs

that were tagged with a

[ChangeEvent] metadata tag. For Flex 2, you convert that tag to

[Bindable] and update the setter to dispatch an Event object.

This section describes these processes.

Binding from all public properties in a class

To make all public properties in a class usable as the source for a data binding expression,

properties defined as properties and properties defined by using both a setter and a getter

method, add the

[Bindable] metadata tag before the class statement:

[Bindable]

public class MyClass { ... }

Although the easiest way to migrate an application that uses binding is to make all public

properties in a class support data binding, it is not necessarily the best practice to use the

[Bindable] metadata tag on an entire class. Doing this causes the compiler to generate more

code, which in turn can affect performance and increase your application’s file size.

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MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manual do Utilizador Página 106