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;
??}??
?}
}