目录

Flex - 事件处理( Event Handling)

Flex使用事件的概念将数据从一个对象传递到另一个对象,具体取决于应用程序中的状态或用户交互。

ActionScript有一个通用的Event类,它定义了处理事件所需的许多功能。 每次在Flex应用程序中发生事件时,都会创建Event类层次结构中的三种类型的对象。

Event具有以下三个关键属性

S.No 财产和描述
1

Type

type说明刚刚发生了什么样的事件。 这可能是单击,初始化,鼠标悬停,更改等。实际值将由MouseEvent.CLICK等常量表示。

2

Target

Event的target属性是对生成事件的组件的对象引用。如果单击id为clickMeButton的Button,则click事件的目标将是clickMeButton

3

CurrentTarget

currentTarget属性改变容器层次结构。 它主要涉及事件流程。

事件流程阶段

事件经历了三个阶段,寻找事件处理程序。

S.No 阶段和描述
1

Capture

在捕获阶段,程序将开始从外部(或顶部)父级到最里面的父级查找事件处理程序。 捕获阶段在触发事件的对象的父级停止。

2

Target

在目标阶段,检查触发事件的组件的事件处理程序。

3

Bubble

冒泡阶段是捕获阶段的反向,通过结构返回,从目标组件的父级开始。

请考虑以下应用程序代码 -

<?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
   width = "100%" height = "100%" minWidth = "500" minHeight = "500" >
   <s:Panel>
      <s:Button id = "clickMeButton" label = "Click Me!" click = "doAction( );" />
   </s:Panel>   
</s:Application>

当用户单击Button时,他或她也单击了Panel和Application。

该事件经历了三个阶段,寻找事件处理程序分配。

Flex事件阶段

让我们按照以下步骤测试Flex应用程序中的事件处理 -

描述
1com.iowiki.client包下创建一个名为HelloWorld的项目,如Flex - Create Application一章中所述。
2 修改HelloWorld.mxml ,如下所述。 保持其余文件不变。
3 编译并运行应用程序以确保业务逻辑按照要求运行。

以下是修改后的mxml文件src/com.iowiki/HelloWorld.mxml

<?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
   width = "100%" height = "100%" minWidth = "500" minHeight = "500">
   <fx:Style source = "/com/iowiki/client/Style.css" />
   <fx:Script>
      <![CDATA[
         protected function reportEvent(event:MouseEvent):void {
            var target:String = event.target.id;
            var currentTarget:String = event.target.id;
            var eventPhase: String;
            if(event.target is Button) {
               var button:Button = event.target as Button;
               target = button.label + " Button";
            } else if(event.target is HGroup) {
               var hGroup:HGroup = event.target as HGroup;
               target = hGroup.id + " HGroup";
            } else if(event.target is Panel) {
               var panel:Panel = event.target as Panel;
               target = panel.id + " Panel";
            }
            if(event.currentTarget is Button) {
               var button1:Button = event.currentTarget as Button;
               currentTarget = button1.label + " Button";
            } else if(event.currentTarget is HGroup) {
               var hGroup1:HGroup = event.currentTarget as HGroup;
               currentTarget = hGroup1.id + " HGroup";
            } else if(event.currentTarget is Panel) {
               var panel1:Panel = event.currentTarget as Panel;
               currentTarget = panel1.id + " Panel";
            }
            var eventPhaseInt:uint = event.eventPhase;
            if(eventPhaseInt == EventPhase.AT_TARGET) {
               eventPhase = "Target";
            } else if(eventPhaseInt == EventPhase.BUBBLING_PHASE) {
               eventPhase = "Bubbling";
            } else if(eventPhaseInt == EventPhase.CAPTURING_PHASE) {
               eventPhase = "Capturing";
            }
            reports.text += " Target: " + target + "\n currentTarget: " +
               currentTarget + "\n Phase: " + eventPhase + "\n----------\n";
         }
      ]]>
   </fx:Script>
   <s:BorderContainer width = "630" height = "480" id = "mainContainer"
      styleName = "container">
      <s:VGroup width = "100%" height = "100%" gap = "10"
         horizontalAlign = "center" verticalAlign = "middle">
         <s:Label id = "lblHeader" text = "Event Handling Demonstration"
            fontSize = "40" color = "0x777777" styleName = "heading" />
         <s:Panel id = "parentPanel" title = "Main Parent"
            click = "reportEvent(event)" width = "500"
            height = "100" includeInLayout = "true" visible = "true">
            <s:layout>
               <s:VerticalLayout  gap = "10" verticalAlign = "middle"
                  horizontalAlign = "center" />
            </s:layout>
            <s:HGroup id = "mainHGroup" click = "reportEvent(event)">
               <s:Button label = "Click Me" click = "reportEvent(event)" />
            </s:HGroup>
         </s:Panel>
         <s:Panel id = "reportPanel" title = "Events" width = "500" height = "230">
            <mx:Text id = "reports" />
         </s:Panel>
      </s:VGroup>
   </s:BorderContainer>
</s:Application>

一旦准备好完成所有更改,让我们像在Flex - Create Application章节中那样在正常模式下编译和运行应用程序 。 如果您的应用程序一切正常,它将产生以下结果:[ 在线试用 ]

Flex事件处理
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