：NumberInput.as 类

package
{
    import flashx.textLayout.operations.InsertTextOperation;
    
    import spark.components.TextInput;
    import spark.events.TextOperationEvent;
    
    [Exclude(name= " restrict ", kind= " property ")]
    
     public  class NumberInput extends TextInput
    {
         public function NumberInput()
        {
            updateRegex();
        }
       
         // regex pattern
         private  var regex:RegExp;
       
         private  var _allowNegative:Boolean =  true;
         /* *
         * Specifies whether negative numbers are permitted.
         * Valid values are true or false.
         *
         * @default true
          */
         public function  set allowNegative(value:Boolean): void
        {
            _allowNegative = value;
            updateRegex();
        }
       
         private  var _fractionalDigits: int =  0;
         /* *
         * The maximum number of digits that can appear after the decimal
         * separator.
         *
         *
         
         The default value is 0
          */
         public function  set fractionalDigits(value: int): void
        {
            _fractionalDigits = value;
            updateRegex();
        }
       
         /* *
         *  @private
          */
         override  public function  set restrict(value:String): void
        {
             throw( new Error( " You are not allowed to change the restrict property of this class.  It is read-only. "));
        }
       
         override  protected function childrenCreated(): void
        {
            super.childrenCreated();
           
             // listen for the text change event
            addEventListener(TextOperationEvent.CHANGING, onTextChange);
        }
       
         public function onTextChange( event:TextOperationEvent): void
        {
             if (regex &&  event.operation  is InsertTextOperation)
            {
                 //  What will be the text if this input is allowed to happen
                 var textToBe:String =  "";
                 //  Check selection
                 if (selectionActivePosition >  0)
                {
                    textToBe += text.substr( 0, selectionActivePosition)
                }
                 // append the newly entered text with the existing text
                textToBe += InsertTextOperation( event.operation).text;
                 if (selectionAnchorPosition >  0)
                {
                    textToBe += text.substr(selectionAnchorPosition, text.length - selectionAnchorPosition);
                }
                 var match:Object = regex.exec(textToBe);
                 if (!match || match[ 0] != textToBe)
                {
                     //  The textToBe didn't match the expression... stop the event
                     event.preventDefault();
                }
                 // special condition checking to prevent multiple dots
                 var firstDotIndex: int = textToBe.indexOf( " . ");
                 if( firstDotIndex != - 1)
                {
                     var lastDotIndex: int = textToBe.lastIndexOf( " . ");
                     if(lastDotIndex != - 1 && lastDotIndex != firstDotIndex)
                         event.preventDefault();
                }
            }
        }
       
         private function updateRegex(): void
        {
             var regexString:String =  " \\d{0,50} ";
             if(_allowNegative)
                regexString =  " ^\\-? " + regexString;
             else
                regexString =  " ^ " + regexString;
             if(_fractionalDigits >  0 )
                regexString +=  " \\.?\\d{0, " + _fractionalDigits.toString() +  " }$ ";
             else
                regexString +=  " $ ";
            regex =  new RegExp(regexString);
        }
    }
}