Question

Can I write a function inside an attribute in flex? Something like this:

<s:Button id="btn" label="text" visible="{foo()}"/>
private function foo():Boolean
{
  //do something
}

It seems it doesn t work at least for me.
I know that I can write like visible="{something == true && somethingElse == false}" etc. But I need it to do more like for loops etc.

Answer 1

这种执行没有约束力——如果因疏漏而发生改变,则不会反映在你的显示名单上。

虽然我认为,这在创建时应当一劳永逸:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               xmlns:mx="library://ns.adobe.com/flex/mx"
               minWidth="955"
               minHeight="600">

    <fx:Script>
        <![CDATA[
            private function foo():Boolean
            {
                return false;
            }
        ]]>
    </fx:Script>

    <s:Button label="text"
              visible="{foo()}" />

</s:Application>

更好的做法是纳入一个介绍模式,利用这里所看到的具有约束力的手段:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               xmlns:mx="library://ns.adobe.com/flex/mx"
               minWidth="955"
               minHeight="600"
               creationComplete="creationCompleteHandler(event)">

    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;

            [Bindable]
            public var presentationVisible:Boolean = true;

            private var timer:Timer = new Timer(500);

            private function foo():void
            {
                presentationVisible = Math.random() > 0.5 ? true : false;
            }

            protected function creationCompleteHandler(event:FlexEvent):void
            {
                timer.addEventListener(TimerEvent.TIMER, timerHandler);
                timer.start();
            }

            protected function timerHandler(event:TimerEvent):void
            {
                foo();
            }
        ]]>
    </fx:Script>

    <s:Button label="text"
              visible="{presentationVisible}" />

</s:Application>

Answer 2

为此:

[Bindable(event="update")]
private function foo():Boolean
{
   return a && b && c;
}

并且,如果某项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或一项或数项的变更,那么:

dispatchEven(new Event("update"));

友情链接