ComboBox下拉列表选择转为手工录入提示

下面自定义class继承ComboBox类，实现的功能是将下拉列表框中的数据通过手工录入检索，而不是通过下拉列表选择，对于下拉列表中数据较多非常方便。需要注意的是，如果ComboBox中有chang事件，需要进行判断ComboBoxId.selectIndex != -1;否则或报空对象异常。

package components.common
{
 import flash.events.Event;
 import flash.events.FocusEvent;
 import flash.events.KeyboardEvent;
 import flash.ui.Keyboard;
 
 import mx.collections.ICollectionView;
 import mx.controls.Alert;
 import mx.controls.ComboBox;
 import mx.core.UIComponent;
 
 import view.customer.viewCustomer;
 
 
 public class AutoComplete extends ComboBox
 {
  public function AutoComplete()
  {
   super();
   init();
  }
  
  private function init():void{
   editable=true;
   rowCount=5;
   selectedIndex=-1;
   isTextBoxStringChange=false;
   isfocusInDropDown=false;
   isAutoComplete=false;
   //伪装成TextBox
   setStyle("cornerRadius",0);
   setStyle("arrowButtonWidth",0);
   setStyle("fontWeight","normal");
   setStyle("paddingLeft",0);     
  }
  
  
  
  //获得焦点时，是否自动弹出下拉框，get set
  private var isfocusInDropDown:Boolean=false;
   
  //是否自动完成,get set
  private var isAutoComplete:Boolean=false;
  
  //类默认过滤函数,get set
  private var _filterFunction:Function = myFilterFunction;
  
  //文本是否发生了变化
  private var isTextBoxStringChange:Boolean=false;
  
  //按下的键是否是退格键
  private var isBackSpaceKeyDown:Boolean=false;
  
  /**
   * 处理退格键按下的情况
   */  
  override protected function keyDownHandler(event:KeyboardEvent):void
  {
   if(!event.ctrlKey&&!event.shiftKey)
   {
    if(event.keyCode == Keyboard.BACKSPACE)
    {
     close();
     isBackSpaceKeyDown=true;
    }
    else
    {
     isBackSpaceKeyDown=false;
    }
    //当按UP键向上选择时，到达最顶时，显示用户原来所需文字
    if(event.keyCode == Keyboard.UP && selectedIndex==0)
    {
     selectedIndex=-1;
    }        
   }
   super.keyDownHandler(event);
  }  
  
  /**
   * 数据源发生变化,数据不为0弹出下拉列表
   */
  override protected function collectionChangeHandler(event:Event):void
  {
   super.collectionChangeHandler(event);
   if(dataProvider.length>0&&text!="")
   {
//    Alert.show(textInput.text+","+textInput.text.length);
    open();
   }
  }
  
  /**
      *  Displays the drop-down list.
      */
     override public function open():void{
      
      if(text!=""){
//       Alert.show(textInput.text+","+text+"open()!!!"+isTextBoxStringChange);
       super.open();
      }
     }
  /**
   * 获得焦点
   */
  override protected function focusInHandler(event:FocusEvent):void{
   if(isfocusInDropDown) open();
   //
   super.focusInHandler(event);
  }
  
  /**
   * 文本发生变化时
   */
  override protected function textInput_changeHandler(event:Event):void
  {
//   Alert.show(textInput.text+" text change!");
   if(textInput.text == ""){
//    Alert.show(textInput.text+",null");
    isTextBoxStringChange=false;
   }
   else{   
//    Alert.show(textInput.text+","+event.toString());
    isTextBoxStringChange=true;
    super.textInput_changeHandler(event);
    invalidateProperties();//调用该方法，随后会触发调用commitProperties()
   }
  }
  
  override protected function commitProperties():void{
   if(isTextBoxStringChange&&textInput.text!=""){
    prompt=text;
    filter();       //进行匹配项的查找
    if(isAutoComplete&&!isBackSpaceKeyDown){
     var autoCompleteString:String="";
     if(dataProvider.length>0)
     {
      autoCompleteString=itemToLabel(dataProvider[0]);
      textInput.setSelection(prompt.length,autoCompleteString.length);
      prompt=autoCompleteString;             
     } 
     else{
      textInput.setSelection(textInput.selectionEndIndex,textInput.selectionEndIndex);
     }
    }
    else{
     textInput.setSelection(textInput.selectionEndIndex,textInput.selectionEndIndex); 
    }
   }    
   super.commitProperties();
  }
  
  /**
   * 与TextBox同样的宽度
   */
  override protected function measure():void
  {
   super.measure();
   measuredWidth=UIComponent.DEFAULT_MEASURED_WIDTH;
  }
  
  /**
   * 过滤操作
   */
  private function filter():void{
   var tmpCollection:ICollectionView = dataProvider as ICollectionView;
   tmpCollection.filterFunction = _filterFunction;
   tmpCollection.refresh();
  }
  
  /**
   * 过滤函数
   */
  private function myFilterFunction(item:Object):Boolean
  {
   var myLabel:String = itemToLabel(item);
   if(myLabel.substr(0,text.length).toLowerCase() == prompt.toLowerCase())
   {
    return true;
   }
   return false;
  }
  
  /************************Get Set 属性**********************************/
  
  public function get FilterFunction():Function{
   return _filterFunction;
  }
  
  public function set FilterFunction(filterFunction:Function):void{
   _filterFunction=filterFunction;
  }
  
  
  public function get IsfocusInDropDown():Boolean{
   return isfocusInDropDown;
  }
  
  public function set IsfocusInDropDown(value:Boolean):void{
   isfocusInDropDown=value;
  }
  
  public function get IsAutoComplete():Boolean{
   return isAutoComplete;
  }
  
  public function set IsAutoComplete(value:Boolean):void{
   isAutoComplete=value;
  }  

 }
}