Flex - 数据绑定

什么是数据绑定？

数据绑定是一个将一个对象的數據与另一个对象綁定的过程。它需要一个源属性、一个目标属性和一个触发事件，该事件指示何时将数据从源复制到目标。

Flex 提供以下三种数据绑定方式

• MXML 脚本中的花括号语法 ({})
• <fx:binding> 标签在 MXML 中
• ActionScript 中的 BindingUtils

数据绑定 – 在 MXML 中使用花括号

以下示例演示了如何使用花括号指定源到目标的数据绑定。

<s:TextInput id = "txtInput1" />
<s:TextInput id = "txtInput2" text = "{txtInput1.text}" />

数据绑定 – 在 MXML 中使用 <fx:Binding> 标签

以下示例演示了如何使用标签指定源到目标的数据绑定。

<fx:Binding source = "txtInput1.text" destination = "txtInput2.text" />
<s:TextInput id = "txtInput1" />
<s:TextInput id = "txtInput2" />

数据绑定 – 在 ActionScript 中使用 BindingUtils

以下示例演示了如何使用 BindingUtils 指定源到目标的数据绑定。

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

      protected function txtInput2_preinitializeHandler(event:FlexEvent):void {
         BindingUtils.bindProperty(txtInput2,"text",txtInput1, "text");
      }      
   ]]>
</fx:Script>

<s:TextInput id = "txtInput1" />
<s:TextInput id = "txtInput2" 
   preinitialize = "txtInput2_preinitializeHandler(event)" />

Flex 数据绑定示例

让我们按照以下步骤，通过创建一个测试应用程序，在 Flex 应用程序中查看皮肤的实际效果：

以下是修改后的 HelloWorld.mxml 文件 src/com/tutorialspoint/client/HelloWorld.mxml 的内容。

<?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/tutorialspoint/client/Style.css" />
   <fx:Script>
      <![CDATA[
         import mx.binding.utils.BindingUtils;   
         import mx.events.FlexEvent;

         protected function txtInput6_preinitializeHandler(event:FlexEvent):void {
            BindingUtils.bindProperty(txtInput6,"text",txtInput5, "text");
         }
      ]]>
   </fx:Script>
   
   <fx:Binding source = "txtInput3.text" destination = "txtInput4.text" />
   <s:BorderContainer width = "500" height = "550" id = "mainContainer" 
      styleName = "container">
      <s:VGroup width = "100%" height = "100%" gap = "50" horizontalAlign = "center" 
         verticalAlign = "middle">
         <s:Label id = "lblHeader" text = "Data Binding Demonstration"
            fontSize = "40" color = "0x777777" styleName = "heading" />
         <s:Panel title = "Example #1 (Using Curly Braces,\{\})" width = "400" 
            height = "100" >
            <s:layout>
               <s:VerticalLayout paddingTop = "10" paddingLeft = "10" />
            </s:layout>
            
            <s:HGroup >
               <s:Label text = "Type here: " width = "100" paddingTop = "6" />
               <s:TextInput id = "txtInput1" />	
            </s:HGroup>
            
            <s:HGroup >
               <s:Label text = "Copied text: " width = "100" paddingTop = "6" />
               <s:TextInput id = "txtInput2" text = "{txtInput1.text}" />
            </s:HGroup>						
         </s:Panel>
         
         <s:Panel title = "Example #2 (Using &lt;fx:Binding&gt;)" width = "400" 
            height = "100" >
            <s:layout>
               <s:VerticalLayout paddingTop = "10" paddingLeft = "10" />
            </s:layout>
            
            <s:HGroup >
               <s:Label text = "Type here: " width = "100" paddingTop = "6" />
               <s:TextInput id = "txtInput3" />	
            </s:HGroup>
            
            <s:HGroup >
               <s:Label text = "Copied text: " width = "100" paddingTop = "6" />
               <s:Label id = "txtInput4" />
            </s:HGroup>						
         </s:Panel>
         
         <s:Panel title = "Example #3 (Using BindingUtils)" width = "400" 
            height = "100" >
            <s:layout>
               <s:VerticalLayout paddingTop = "10" paddingLeft = "10" />
            </s:layout>
            
            <s:HGroup >
               <s:Label text = "Type here: " width = "100" paddingTop = "6" />
               <s:TextInput id = "txtInput5" />	
            </s:HGroup>
            
            <s:HGroup >
               <s:Label text = "Copied text: " width = "100" paddingTop = "6" />
               <s:TextInput enabled = "false" id = "txtInput6" 
                  preinitialize = "txtInput6_preinitializeHandler(event)" />
            </s:HGroup>						
         </s:Panel>
      </s:VGroup>	 
   </s:BorderContainer>	
</s:Application>

完成所有更改后，让我们像在Flex - 创建应用程序章节中那样，以普通模式编译并运行应用程序。如果应用程序一切正常，它将产生以下结果：[ 在线尝试 ]