Flex使用事件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具有通用事件 class,它定义了处理事件所需的大部分功能.每次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.
事件具有以下三个关键属性
Sr.No | Property&说明 |
---|---|
1 | 键入 类型说明刚刚发生的事件类型.这可能是click,initialize,mouseover,change等.实际值将由MouseEvent.CLICK等常量表示. |
2 | 目标 目标 Event的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,则该click事件的目标将是clickMeButton |
3 | CurrentTarget currentTarget 属性会改变容器层次结构.它主要处理事件流程. |
事件经历了三个阶段,寻找事件处理程序.
Sr.No | Phase&说明 |
---|---|
1 | 捕获 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 | 目标 在目标阶段,检查触发事件的组件事件处理程序. |
3 | 冒泡 冒泡阶段与捕获阶段相反,从目标组件的父级开始,通过结构返回. |
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>
当用户点击Button时,他或她也点击了小组和应用程序.
该事件经历了三个阶段,寻找事件处理程序分配.
让我们按照以下步骤测试Flex应用程序中的事件处理 :
Step | 描述 |
---|---|
1 | 在包 com下创建名为 HelloWorld 的项目. it1352.client ,如 Flex - 创建应用程序章节中所述. |
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. |
以下是内容修改后的mxml文件 src/com.it1352/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/IT屋/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>
完成所有更改后,让我们按照正常模式编译并运行应用程序,就像我们在Flex - 创建应用程序章节.如果您的应用程序一切正常,它将产生以下结果: