ActionScript 3 带缓存的简单加载管理器

Posted 2021-05-23

package {
import flash.display.Loader;
import flash.display.LoaderInfo;
import flash.events.Event;
import flash.events.IOErrorEvent;
import flash.net.URLRequest;
import flash.utils.Dictionary;

/**
 * The simple load manager for multiple loaders.
 * It doesn't handle progress event but caches each loaded content which is shared between clients
 * Content should be allowed by flash player security
 */
public class SharedLoadManager
{
	private static var _cache:Dictionary = new Dictionary;
	private static var _freeLoaders:Vector.<Loader>;
	private static var _activeLoaders:Dictionary = new Dictionary();
	private var _pendingHandlers:Dictionary = new Dictionary();

	/**
	 * start load display object
	 * @param uri
	 * @param loadHandler function called when the load complete,
	 * if the object with such uri already have been loaded the function called immediately
	 * the function takes one parameter of type Object
	 * (which is a loaded content) on success or null on load error
	 */
	public function load(uri:String,loadHandler:Function):void
	{
		if(_cache[uri] != null)
		{
			loadHandler(_cache[uri]);
			return;
		}

		if(_pendingHandlers[uri] == null)
		{
			_pendingHandlers[uri] = new Vector.<Function>;
		}
		_pendingHandlers[uri].push(loadHandler);

		if(_activeLoaders[uri] == null)
		{
			var loader:Loader = getLoader();
			_activeLoaders[loader] = uri;
			loader.load(new URLRequest(uri));
		}
	}

	/**
	 * cancel the loading which was previously initiated by the load() method
	 * @param uri
	 * @param loadHandler
	 */
	public function cancel(uri:String, loadHandler:Function):void
	{
		if(_pendingHandlers[uri] != null)
		{
			for (var i:int=0;i<_pendingHandlers[uri].length;i++)
			{
				if(_pendingHandlers[uri][i] == loadHandler)
				{
					_pendingHandlers[uri].splice(i,1);
					break;
				}
			}
			if(_pendingHandlers[uri].length == 0)
			{
				_activeLoaders[uri].close();
				_activeLoaders[uri] = null;
				delete _activeLoaders[uri];
			}
		}
	}

	/**
	 * remove cached objects and free loaders
	 * @param disposeLoaders if false than loaders doesn't disposed
	 */
	public function clearCache(disposeLoaders:Boolean = true):void
	{
		for (var uri:String in _cache)
		{
			_cache[uri] = null;
			delete _cache[uri];
		}
		if(disposeLoaders && _freeLoaders != null)
		{
			while(_freeLoaders.length)
			{
				_freeLoaders.shift();
			}
		}
	}

	private function getLoader():Loader
	{
		if(_freeLoaders != null && _freeLoaders.length > 0)
		{
			return _freeLoaders.shift();
		}
		var loader:Loader = new Loader();
		loader.contentLoaderInfo.addEventListener(Event.COMPLETE, completeLoadHandler);
		loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, errorLoadHandler);
		return loader;
	}

	private function errorLoadHandler(event:IOErrorEvent):void
	{
		handleResult(LoaderInfo(event.target));
	}

	private function completeLoadHandler(event:Event):void
	{
		handleResult(LoaderInfo(event.target));
	}

	private function handleResult(loaderInfo:LoaderInfo):void
	{
		var uri:String = _activeLoaders[loaderInfo.loader];
		var handlers:Vector.<Function> = _pendingHandlers[uri];
		if(handlers != null)
		{
			while(handlers.length)
			{
				var handler:Function = handlers.shift();
				handler(loaderInfo.content);
			}
			_pendingHandlers[uri] = null;
			delete _pendingHandlers[uri];
		}
		if(loaderInfo.content)
		{
			_cache[uri] = loaderInfo.content;
			loaderInfo.loader.unload();
		}
		_activeLoaders[loaderInfo.loader] = null;
		delete _activeLoaders[loaderInfo.loader];
		if(_freeLoaders == null)
		{
			_freeLoaders = new Vector.<Loader>;
		}
		_freeLoaders.push(loaderInfo.loader);
	}
}
}