flex4的Scroller滚动速度的控制

Scroller的viewport为Group时，滚动鼠标滑轮，Scroller滚动的速度很慢，Scroller的viewport为VGroup时， 滚动鼠标滑轮，Scroller滚动的速度很快，有没有什么办法控制 Scroller的滚动速度呢？解决方案如下：
1.新建VScrollBar的子类
MyVScrollerBar.as
package
{

import flash.events.MouseEvent;



import mx.core.mx_internal;



import spark.components.VScrollBar;

import spark.core.IViewport;



use namespace mx_internal;



[Style(name="movementDelta",inherit="yes",type="number",format="length")]

public class MyVScrollerBar extends VScrollBar

{

public function MyVScrollerBar()

{

setStyle("movementDelta",30);

}



override mx_internal function mouseWheelHandler(event:MouseEvent):void

{

var viewport:IViewport = this.viewport;

if ( viewport == null || !viewport.visible || event.isDefaultPrevented() )

return;



var direction:int = (event.delta > 0) ? -1 : (event.delta < 0) ? 1 : 0;

var movement:Number = getStyle("movementDelta");

viewport.verticalScrollPosition += movement * direction;

event.preventDefault();

}



}
}

2.新建外观类

MyVScrollerBarSkin.mxml
< ?xml version="1.0" encoding="utf-8"?>
< s:SparkSkin xmlns:fx="http://ns.adobe.com/mxml/2009" 

xmlns:s="library://ns.adobe.com/flex/spark" 

xmlns:local="*">

< fx:Metadata>

< ![CDATA[ 

[HostComponent("spark.components.Scroller")]

]]>

< /fx:Metadata> 



< fx:Script>

< ![CDATA[ 



override public function beginHighlightBitmapCapture() : Boolean

{

var needUpdate:Boolean = super.beginHighlightBitmapCapture();

graphics.beginFill(0);

graphics.drawRect(0,width,height);

graphics.endFill();



return needUpdate;

}



override public function endHighlightBitmapCapture() : Boolean

{

var needUpdate:Boolean = super.endHighlightBitmapCapture();

graphics.clear();

return needUpdate;

}

]]>

< /fx:Script>

< local:MyVScrollerBar id="verticalScrollBar" visible="false" />

< s:HScrollBar id="horizontalScrollBar" visible="false" />




< /s:SparkSkin>


3.将Scroller的skinClass设为刚刚新建的外观类MyVScrollerBarSkin
< ?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">



< s:Scroller width="400" height="400" skinClass="MyVScrollerBarSkin">

< s:Group width="100%" height="100%">

< s:Rect width="100%" height="1200">

< s:fill>

< s:SolidColor color="0x338899"/>

< /s:fill>

< /s:Rect>

< /s:Group>

< /s:Scroller>
< /s:Application>

ok，困扰了两天的问题搞定。

通过研究,其实没有必要这么麻烦,以前的flex3的SDK直接设置一个步长就可以解决问题,而spark组建中的scroller组件把这个属性取消了,通过查找例子,发现都是转载的楼主的方法,这的确太麻烦了..
 
后来在一个国外网站搜到一个解决办法,每一个scroller都有一个mouseWheelChanging方法,当滚动鼠标中轮的时候调用,而后就可以在这个函数中进行判断,如下:
 我的滚动条id=mainScroller
 protected function mainScroller _mouseWheelChangingHandler(event:FlexMouseEvent):void
 {
         event.preventDefault();
         var modifier:int = 5;
         var delta:Number = Number(event.delta) * modifier;
         var viewport:IViewport = mainScroller.verticalScrollBar.viewport;
         var vPos:Number = viewport.verticalScrollPosition;
         var maximum:Number = mainScroller.verticalScrollBar.maximum;
                                 
        if (delta < 0) 
        {
                 mainScroller.verticalScrollBar.viewport.verticalScrollPosition =  Math.min(vPos - delta,maximum) ;        
        }
         else
         {
                 mainScroller.verticalScrollBar.viewport.verticalScrollPosition = Math.max(vPos - delta,0);
         }
 
}
 

转载：http://bbs.9ria.com/thread-114341-1-1.html