创建受约束的布局

让页面上的组件随窗体的改变而改变。所有容器的布局方式都应设置为绝对方式（absolute）。

Demo：


<?xml version="1.0" encoding="utf-8"?>


<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">


<!--Use x,y to define the position of the component;


Use width,height to define the size of the component;


Use left,right,top,bottom to define the distance between the component border and


the container border;


-->


<mx:Label x="20" y="60" text="Email"/>


<mx:TextInput y="60" right="60" left="90"/>


<mx:Label x="20" y="90" text="Comments"/>


<mx:TextArea left="90" right="60" top="90" bottom="190"/>


<mx:Button label="Send" right="60" bottom="150"/>




</mx:Application>