Actionscript 3 空对象错误消息答案

【问题标题】：Actionscript 3 Null Object Error MessageActionscript 3 空对象错误消息
【发布时间】：2010-08-08 02:56:25
【问题描述】：

我正在构建一个仅限 AS3 的项目，但运行时错误提示“无法访问空对象引用的属性或方法”。

这是我的代码：

main.as

       public class videoMain extends Sprite{

         private var videoPlayer:Player;

       public function videoMain (){
         loadPlayer()
         loadProgress();
       }

       private function loadProgress():void{

        //the code below gave me null object error.....     
        var byteLoaded:Number=videoPlayer.videoBytesLoaded; //the problem code
        var byteTotal:Number=videoPlayer.videoBytesTotal;  //the problem code

        var percent:Number=Math.floor(byteLoaded/byteTotal)*100;
        }

        private function loadPlayer():void{

        videoPlayer= new Player();
        videoPlayer.createPlayer();
    }

}

播放器.as

public function createPlayer():void{

    _loader = new Loader();
    _loader.contentLoaderInfo.addEventListener(Event.INIT, onLoaderInit);
    _loader.load(new URLRequest(playerType));

    }

public function get videoBytesLoaded():Number{
    return _Player.getVideoBytesLoaded();  //youtube api method
    }

public function get videoBytesTotal():Number{
    return _Player.getVideoBytesTotal;    //youtube api method
    }

 private function onLoaderInit(event:Event):void {
    _Player=_loader.content;
        //only show part of codes....
    }

I appreciate any help....Thanks!!!!!

【问题讨论】：

标签： apache-flex flash actionscript null

【解决方案1】：

_Player 仅在 Event.INIT 触发后定义，因此在定义 _Player 值之前的任何调用都会引发错误。

你至少应该有这个：

public function videoMain (){
     loadPlayer()
   }

private function onLoaderInit(event:Event):void {
    _Player=_loader.content;
    //only show part of codes....
    loadProgress();

}

但是进度事件不是静态的，所以你真的应该有一个 enterFrame 事件监听器来监听变化的值......

private function onLoaderInit(event:Event):void {
    _Player=_loader.content;
    //only show part of codes....

    addEventListener(Event.ENTER_FRAME , enterFrameListener);
}

private function enterFrameListener(event:Event):void
{
    loadProgress();
    // and here you add some way to remove this event listener when 
    // the video is fully loaded
}

【讨论】：