在非文档类中stage的用法

在非文档类中stage的用法

我想写个Code类,就是检测A键落下之后 Code.left = true;就可以了.

代码如下：
package {
       import flash.events.KeyboardEvent;
       import flash.display.Stage;
       import flash.ui.Keyboard;
       import flash.display.MovieClip;
       public class Code extends MovieClip {
              private var codeStage:Stage;
              public var Left:Boolean = false;
              public function Code(evt:Stage):void {
                     init(evt);

              }
              public function init(initStage:Stage):void {
                     codeStage = initStage;
                     codeStage.addEventListener(KeyboardEvent.KEY_DOWN,KeyPressed);
                     codeStage.addEventListener(KeyboardEvent.KEY_UP,KeyReleased);
              }
              private function KeyPressed(evt:KeyboardEvent):void {
                     switch (evt.keyCode) {
                            case Keyboard.LEFT :
                                   Left = true;
                                   break;
                     }
              }
              private function KeyReleased(evt:KeyboardEvent):void {
                     switch (evt.keyCode) {
                            case Keyboard.LEFT :
                                   Left = false;

                                   break;
                     }
              }
       }
}