apache-flex - 如何阻止数据网格的第一行 itemRenderer 实例化/添加/初始化/等两次？

Question

在 Flex DataGrid 的第一行中，itemRenderer 将初始化两次。跟踪结果显示 flex 框架可能正在创建第一行的 itemRenderer 的两个实例。在一个更复杂的应用程序中，itemRenderer 包含一个数据绑定(bind)的 ColorPicker，我们看到由于这个问题而发生了无限循环。只有第一行的 itemRenderer 被初始化了两次。有没有办法覆盖 flex 的行为并阻止这种情况发生？下面的代码演示了这个问题:

主要应用:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="on_initialize(event);">
<mx:Script>
<![CDATA[
/**
 * This experiment shows how the first row's itemrenderer is instantiated/added/initialized twice.
 * We've never even noticed this before we found that a data-bound ColorPicker enters a infinite
 * loop when it is within an itemRenderer.
 */
    import mx.collections.ArrayCollection;
    import mx.events.FlexEvent;

    private var dg_array:Array;
    private var dg_arrayCollection:ArrayCollection;

    private function on_initialize(event:FlexEvent):void {
        dg_array = new Array();
        dg_arrayCollection = new ArrayCollection();
        dg_arrayCollection.addItem("item 1");
        dg_arrayCollection.addItem("item 2");

        dg.dataProvider = dg_arrayCollection;
    }
]]>
</mx:Script>
<mx:DataGrid id="dg" width="100%" height="100%" rowCount="5">
    <mx:columns>
        <mx:DataGridColumn headerText="Name" itemRenderer="SimpleItemRenderer"/>
    </mx:columns>
</mx:DataGrid>
</mx:Application>

简单项目渲染器:

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" width="400" height="300" initialize="//on_initialize(event);">
<mx:Script>
    <![CDATA[
        import mx.events.FlexEvent;

        [Bindable]
        override public function set data(value:Object):void { _data = value; }                 
        override public function get data():Object { return _data; }
        private var _data:Object;

        private function on_initialize_textInput(event:FlexEvent):void {
            trace("initialize:event.target="+event.target+", " + _data); // runs twice, for the first item only

        }

        private function on_creationComplete_textInput(event:FlexEvent):void {
            trace("creationComplete:event.target="+event.target+", " + _data); // runs twice, for the first item only
        }
    ]]>
</mx:Script>
<mx:TextInput text="{data}" id="textInput" initialize="on_initialize_textInput(event);" creationComplete="on_creationComplete_textInput(event);"/>
</mx:Canvas>

缩写输出:

初始化:event.target=ItemRenderers0.dg...SimpleItemRenderer12.textInput，空
初始化:event.target=ItemRenderers0.dg...SimpleItemRenderer24.textInput，空
creationComplete:event.target=ItemRenderers0.dg...SimpleItemRenderer24.textInput，项目 1
初始化:event.target=ItemRenderers0.dg...SimpleItemRenderer29.textInput，空
creationComplete:event.target=ItemRenderers0.dg...SimpleItemRenderer29.textInput，第 2 项
creationComplete:event.target=ItemRenderers0.dg...SimpleItemRenderer12.textInput，项目 1

Answer 1

Updated link to the series by Peter Ent on itemRenders