flex 电子白板，共享对象

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
creationComplete="drawInit()"
layout="vertical">

<mx:Script>
<![CDATA[
import mx.core.UIComponent;
import mx.controls.Alert;

private var shape:String;
private var flag:Boolean;
private var sx:Number;
private var sy:Number;
private var ex:Number;
private var ey:Number;
private var sprite:Sprite;
private var uic:UIComponent;
private var i:int;
private var arr:Array=new Array();
/**
* 初始化
* */
private function drawInit():void
{
myCanvas.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
myCanvas.addEventListener(MouseEvent.MOUSE_MOVE, onMouseMove);
myCanvas.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
}
private function onMouseDown(e:MouseEvent):void
{
flag=true;
sx=myCanvas.mouseX;
sy=myCanvas.mouseY;
sprite=new Sprite();
uic=new UIComponent();
myCanvas.addChildAt(uic, i++);
uic.addChild(sprite);
}
private function onMouseMove(e:MouseEvent):void
{
if (flag)
{
draw(shape);
}
}
private function onMouseUp(e:MouseEvent):void
{
flag=false;
}
private function setShape(str:String):void
{
shape=str;
}
/**
* 画线
* */
private function draw(s:String):void
{
ex=myCanvas.mouseX;
ey=myCanvas.mouseY;
if (s == "line")
{
sprite.graphics.clear(); //清除
sprite.graphics.lineStyle(hs.value, cp.selectedColor); //设置样式
sprite.graphics.moveTo(sx, sy); //开始坐标
sprite.graphics.lineTo(ex, ey); //移动坐标

}
}
/**
* 撤销
* */
private function undo():void
{
if (i <= 0)
{
return;
}
//放入撤销集合
arr.push(myCanvas.getChildAt(--i)); //添加元素到最后 ，unshift添加元素到最前
myCanvas.removeChildAt(i);
}
/**
* 重做
* */
private function redo():void
{
if (arr.length <= 0)
{
return;
}
//从撤销集合取出
myCanvas.addChildAt(UIComponent(arr.pop()), i++); //arr.pop()表示删除最后一个，并返回 ，shift表示删除第一个元素，并返回
}
]]>
</mx:Script>
<mx:TabNavigator width="768"
height="401">
<mx:VBox label="FLEX画图"
width="100%"
height="100%">
<mx:Canvas width="100%"
   height="315"
   id="myCanvas"
   backgroundColor="#006699">
</mx:Canvas>
<mx:HBox width="100%"
height="44"
verticalAlign="middle">
<mx:Button label="画直线"
   click="setShape('line')"/>
<mx:Button label="撤销"
   click="undo()"/>
<mx:Button label="重做"
   click="redo()"/>
<mx:HSlider id="hs"
value="3"/>
<mx:ColorPicker id="cp"
selectedColor="red"/>
<mx:Button label="清屏"
   click="myCanvas.removeAllChildren();i=0"/>
</mx:HBox>
</mx:VBox>
</mx:TabNavigator>

</mx:Application>