flex 自动显示水平滚动条

<mx:Tree/> 只会自动显示垂直滚动条而不会自动显示水平滚动条，貌似是因为没有对

maxHorizontalScrollPosition属性进行动态的处理，一下重写tree组件，可以自动显示水平滚动条。

 
 

package?com.common.tree?{? ?
  
  
import?flash.events.Event;? ?
  
  
?
  
  
import?mx.controls.Tree;? ?
  
  
import?mx.core.ScrollPolicy;? ?
  
  
import?mx.core.mx_internal;? ?
  
  
?
  
  
/**? ?
  
  
*?自动显示横向滚动条? ?
  
  
*?@author?chensong? ?
  
  
*? ?
  
  
*/? ?
  
  
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);? ?
  
  
}? ?
  
  
}? ?
  
  
}??