flex tree自动显示横向滚动条实现代码

package com.anydata.consumer.components

{

import flash.events.Event;

import mx.controls.Tree;

import mx.core.ScrollPolicy;

import mx.core.mx_internal;

public class AutoSizeTree extends Tree

{

public function AutoSizeTree()

{

super();

horizontalScrollPolicy=ScrollPolicy.AUTO;

}

override public function get maxHorizontalScrollPosition():Number

{

if (isNaN(mx_internal::_maxHorizontalScrollPosition))

return 0;

return mx_internal::_maxHorizontalScrollPosition;

}

override public function set maxHorizontalScrollPosition(value:Number):void

{

mx_internal::_maxHorizontalScrollPosition=value;

dispatchEvent(new Event(“maxHorizontalScrollPositionChanged”));

scrollAreaChanged=true;

invalidateDisplayList();

}

override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void

{

var diffWidth:Number=measureWidthOfItems(0, 0) – (unscaledWidth – viewMetrics.left – viewMetrics.right);

var indentation:Number=getStyle(“indentation”);

if (diffWidth <=0)

maxHorizontalScrollPosition=NaN;

else

maxHorizontalScrollPosition=diffWidth + indentation;

super.updateDisplayList(unscaledWidth, unscaledHeight);

}

}

}