ActionScript3：在一个类中通过 addEventListener 读取文件，如何将数据传递给不同的类

Question

有很多与我类似的问题，但没有一个能解决我的问题。

我有这门课-

package com.test
{
    import flash.events.*;
    import flash.net.*;
    
    import com.test.LogUtils;
    import mx.logging.ILogger;
    
    public class LoadExtUrl extends EventDispatcher
    {
        private var baseUrl:String;
        private var log:ILogger = LogUtils.getLogger(LoadExtUrl);
        
        public function LoadExtUrl()
        {
            log.debug ("100 In LoadExtUrl()");
            super(null);
        }
        
        public function loadBaseUrl():String
        {
            var loader:URLLoader = new URLLoader();
            loader.dataFormat = URLLoaderDataFormat.VARIABLES;
            loader.addEventListener(Event.COMPLETE, urlLoader_completeHandler);
            
            function urlLoader_completeHandler(event:Event):void
            {
                var loader:URLLoader = URLLoader(event.target);
                this.baseUrl = loader.data.baseurl;
                dispatchEvent(new Event("GOTRESULTS"));
                log.debug ("200 In LoadExtUrl, baseUrl="+this.baseUrl);
            }
            
            loader.load(new URLRequest("sri-config-files/url.properties"));
            
            log.debug ("300 In LoadExtUrl, baseUrl="+this.baseUrl);
            return this.baseUrl;
        }
    }
}

现在我想在许多其他类中读取 baseUrl 的值。

在另一个类中，我有以下代码 -

public class UrlHelper
{
    public static var myLoadExtUrl:LoadExtUrl = new LoadExtUrl();
    public static var baseUrl:String;
    
    public function UrlHelper()
    {}
    
    public static function getBaseUrl():void
    {
        myLoadExtUrl.addEventListener("GOTRESULTS", xmlLoadCompleted);
        log.debug("400 In UrlHelper, baseUrl ="+baseUrl);
    }
    
    private static function xmlLoadCompleted(e:Event):void 
    {
        baseUrl=myLoadExtUrl.loadBaseUrl();
        log.debug("500 In UrlHelper, baseUrl ="+baseUrl);
    }
}

记录顺序 -

100 In LoadExtUrl()
300 In LoadExtUrl, baseUrl=null
200 In LoadExtUrl, baseUrl=http://abcxyz.com:8080/

400 In UrlHelper, baseUrl =null --> here only I need the value

我该如何解决这个问题？

Answer 1

我想我需要写一些解释。

什么是异步操作？这是一个操作

• 需要一些（最初未知或无法确定）时间才能完成
• 不阻塞代码执行，简单来说，当你开始加载代码时，不会停止等待操作完成，它会立即开始执行剩下的代码，而不考虑那个操作状态李>

因此，您正在构建的事物中的实际事件流是：

1. UH 类告诉 LEU 类开始加载
2. ...一段时间过去了...
3. LEU 类检测到加载过程结束。
4. 加载的数据可用。
5. LEU 调度自定义事件。
6. UH 检测到事件并最终CAN获取数据。

所以，LoadExtUrl 类：

package
{
    import flash.events.Event;
    import flash.events.EventDispatcher;
    
    import flash.net.URLLoader;
    import flash.net.URLRequest;
    import flash.net.URLLoaderDataFormat;
    
    public class LoadExtUrl extends EventDispatcher
    {
        private var baseUrl:String;
        private var loader:URLLoader;
        
        // Interface method.
        public function loadBaseUrl():String
        {
            var aRequest:URLRequest;
            
            // Form the HTTP request.
            aRequest = new URLRequest;
            aRequest.url = "sri-config-files/url.properties";
            
            // Initiate the loading process.
            loader = new URLLoader;
            loader.dataFormat = URLLoaderDataFormat.VARIABLES;
            loader.addEventListener(Event.COMPLETE, onLoad);
            loader.load(aRequest);
            
            // Data are NOT available yet at this point.
        }
        
        // Data loading COMPLETE handler.
        private function onLoad(e:Event):void
        {
            // Data are AVAILABLE at this point.
            
            // Extract the data.
            baseUrl = loader.data.baseurl;
            
            // Clean up.
            loader.removeEventListener(Event.COMPLETE, onLoad);
            loader = null;
            
            // Tell anyone willing to listen about the data availability.
            var anEvent:Event;
            
            // Feel free to use predefined constants instead of custom
            // event names. It will protect you against typo errors.
            anEvent = new Event(Event.COMPLETE);
            dispatchEvent(anEvent);
        }
    }
}

使用方法：

public class UrlHelper
{
    static public var baseUrl:String;
    
    static private var loadExt:LoadExtUrl;
    
    // Interface method.
    static public function getBaseUrl():void
    {
        // Data are NOT available yet at this point.

        loadExt = new LoadExtUrl;

        // Data are NOT available yet at this point.
        
        // Subscribe to the very same event name
        // that class is going to dispatch.
        loadExt.addEventListener(Event.COMPLETE, onAnswer);

        // Data are NOT available yet at this point EITHER.
        // Loading is an asynchronous operation. We started
        // the loading but we have to wait until the data are available.
    }
    
    // This handler will be invoked when data are available.
    static private function onAnswer(e:Event):void 
    {
        // Data are AVAILABLE at this point.
        
        // Extract the data.
        baseUrl = loadExt.baseUrl;
        
        // Clean up.
        loadExt.removeEventListener(Event.COMPLETE, onAnswer);
        loadExt = null;
        
        // You are free to use the obtained data at this point.
        // ...
    }
}