我注意到Flex中绑定的意外行为，我的代码如下：
申请代码
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" horizontalAlign="center" xmlns:Model="Model.*">
<mx:Script>
<![CDATA[
import Model.DataDummy;
]]>
</mx:Script>
<mx:HBox width="100%" horizontalGap="30">
<mx:Button id="buttonChange1" label="Change property value" click="myDummy._resetMyProperty();" />
<mx:Label id="labelRaw" text="{'My Property=' + myDummy.MyProperty}" opaqueBackground="#DDDDDD" />
<mx:Label id="labelFormatted" text="{'My Property formatted=' + myDummy.MyPropertyFormatted}" opaqueBackground="#DDDDDD" />
</mx:HBox>
<Model:MyDummy id="myDummy" />
<mx:DataGrid id="dataGrid"
width="100%" dataProvider="{DataDummy.Dummies}">
<mx:columns>
<mx:DataGridColumn dataField="MyProperty" headerText="My property" />
<mx:DataGridColumn dataField="MyPropertyFormatted" headerText="My property Formatted" />
</mx:columns>
</mx:DataGrid>
<mx:Button id="buttonChange2" click="{for each ( var d:MyDummy in DataDummy.Dummies ){d._resetMyProperty();}}" label="Change property value in DataGrid" />
</mx:Application>
Model.MyDummy类代码
package Model
{
import flash.events.EventDispatcher;
import mx.formatters.NumberFormatter;
import mx.utils.StringUtil;
[Bindable]
public class MyDummy extends EventDispatcher
{
/*** Constructor ***/
public function MyDummy()
{
this._resetMyProperty();
}
/*** Properties ***/
private var _myProperty:Number;
public function get MyProperty():Number
{
return _myProperty;
}
public function set MyProperty(value:Number):void
{
if ( value !== _myProperty )
{
_myProperty = value;
//var event:Event = new Event("ID_Changed");
//this.dispatchEvent(event);
}
}
//[Bindable (event="ID_Changed", type="flash.events.Event")]
public function get MyPropertyFormatted():String
{
var idFormatted:String = "";
if ( ! isNaN(this.MyProperty) )
{
var formatter:NumberFormatter = new NumberFormatter();
formatter.precision = 2;
idFormatted = formatter.format(this.MyProperty);
}
else
idFormatted = MyProperty.toString();
return StringUtil.substitute( "{0} (My property has been formatted)", idFormatted );
}
/*** Methods ***/
public function _resetMyProperty():void
{
this.MyProperty = Math.round(Math.random() * 1000000000);
}
}
}
Model.DataDummy类代码
package Model
{
import mx.collections.ArrayCollection;
public class DataDummy
{
private static var _dummies:ArrayCollection;
public static function get Dummies():ArrayCollection
{
if ( _dummies == null )
{
_dummies = new ArrayCollection();
_dummies.addItem(new MyDummy());
_dummies.addItem(new MyDummy());
}
return _dummies;
}
}
}
行为如下：
我的观点是：
1.一方面，因为我将控件绑定到某个对象的单个实例，所以绑定不会触发他的只读属性。
2.另一方面，当我在同一个特定对象的集合上绑定控件时，绑定将触发每个属性（只读或不读）。
如果我希望在第1点的readonly属性上触发绑定，我必须在readonly属性'MetaTag上调度一个事件，并根据此事件触发它们的绑定（如显示代码中的注释） Model.MyDummy类。）。
为什么这种行为有所不同？我想准确理解ArrayCollection实例的绑定对单个实例的绑定没有做什么。
感谢您的帮助。
答案 0 :(得分：2)
我认为正确的代码如下所示。
首先，我们的model.MyDummy班级：
package model
{
import flash.events.EventDispatcher;
import mx.events.PropertyChangeEvent;
import mx.formatters.NumberFormatter;
import mx.utils.StringUtil;
public class MyDummy extends EventDispatcher
{
//------------------------------------------------------------------------------
//
// Constructor
//
//------------------------------------------------------------------------------
public function MyDummy()
{
resetMyProperty();
}
//------------------------------------------------------------------------------
//
// Properties
//
//------------------------------------------------------------------------------
//--------------------------------------
// myProperty
//--------------------------------------
private var _myProperty:Number;
[Bindable(event="propertyChange")]
public function get myProperty():Number
{
return _myProperty;
}
public function set myProperty(value:Number):void
{
if (_myProperty == value)
return;
var oldPropertyValue:Number = _myProperty;
var oldFormatted:String = myPropertyFormatted;
_myProperty = value;
dispatchEvent(PropertyChangeEvent.createUpdateEvent(this, "myProperty", oldPropertyValue, value));
dispatchEvent(PropertyChangeEvent.
createUpdateEvent(this, "myPropertyFormatted", oldFormatted, myPropertyFormatted));
}
[Bindable(event="propertyChange")]
public function get myPropertyFormatted():String
{
var idFormatted:String = "";
if (!isNaN(myProperty))
{
var formatter:NumberFormatter = new NumberFormatter();
formatter.precision = 2;
idFormatted = formatter.format(myProperty);
}
else
idFormatted = myProperty.toString();
return StringUtil.substitute("{0} (My property has been formatted)", idFormatted);
}
//------------------------------------------------------------------------------
//
// Methods
//
//------------------------------------------------------------------------------
public function resetMyProperty():void
{
myProperty = Math.round(Math.random() * 1000000000);
}
}
}
我们正在触发propertyChange事件，以便可以从collectionChangeEvent ArrayCollection触发propertyChange（它会自动监听model.DataDummy事件。）
然后是我们的package model
{
import mx.collections.ArrayCollection;
import mx.events.CollectionEvent;
public class DataDummy
{
//------------------------------------------------------------------------------
//
// Constructor
//
//------------------------------------------------------------------------------
public function DataDummy()
{
dummies = new ArrayCollection();
dummies.addItem(new MyDummy());
dummies.addItem(new MyDummy());
}
//------------------------------------------------------------------------------
//
// Variables
//
//------------------------------------------------------------------------------
[Bindable]
public var dummies:ArrayCollection;
}
}
课程：
[Bindable]我们不使用静态来利用与<mx:Application horizontalAlign="center" layout="vertical" xmlns:model="model.*" xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:Script>
<![CDATA[
//------------------------------------------------------------------------------
//
// Event Handlers
//
//------------------------------------------------------------------------------
protected function buttonChange2_clickHandler(event:MouseEvent):void
{
for each (var d:MyDummy in dataProvider.dummies)
{
d.resetMyProperty();
}
}
]]>
</mx:Script>
<mx:HBox horizontalGap="30" width="100%">
<mx:Button click="myDummy.resetMyProperty();" id="buttonChange1" label="Change property value" />
<mx:Label id="labelRaw" opaqueBackground="#DDDDDD" text="{'My Property=' + myDummy.myProperty}" />
<mx:Label id="labelFormatted" opaqueBackground="#DDDDDD"
text="{'My Property formatted=' + myDummy.myPropertyFormatted}" />
</mx:HBox>
<model:MyDummy id="myDummy" />
<model:DataDummy id="dataProvider" />
<mx:DataGrid dataProvider="{dataProvider.dummies}" id="dataGrid" width="100%">
<mx:columns>
<mx:DataGridColumn dataField="myProperty" headerText="My property" />
<mx:DataGridColumn dataField="myPropertyFormatted" headerText="My property Formatted" />
</mx:columns>
</mx:DataGrid>
<mx:Button click="buttonChange2_clickHandler(event)" id="buttonChange2" label="Change property value in DataGrid" />
</mx:Application>
metatag的数据绑定。
最后我们的主要课程改变很小：
[Bindable(event="propertyChange")]正如您所看到的，所有绑定都按预期工作。
P.S。 [Bindable]相当于简单myPropertyFormatted，但这样可以避免[Bindable] getter上的编译器警告。实际上，使用简单的mxmlc形式会导致dispatchEvent编译器自己生成[Bindable]代码。您可以使用myPropertyFormatted标记中的特定事件来控制更多内容。例如，在我们的例子中，我们可以为{{1}}启动事件。
P.P.S。我已经改变了类似C＃的命名约定，以反映实际的ActionScript / MXML。