update download system

Assets/YooAsset/Runtime/DownloadSystem/DownloadSystem.cs

@@ -6,6 +6,11 @@ using UnityEngine.Networking;
 
 namespace YooAsset
 {
+	/// <summary>
+	/// 自定义下载器的请求委托
+	/// </summary>
+	public delegate UnityWebRequest DownloadRequestDelegate(string url);
+
 	/// <summary>
 	/// 1. 保证每一时刻资源文件只存在一个下载器
 	/// 2. 保证下载器下载完成后立刻验证并缓存
@@ -17,10 +22,15 @@ namespace YooAsset
 		private static readonly List<string> _removeList = new List<string>(100);
 
 
+		/// <summary>
+		/// 自定义下载器的请求委托
+		/// </summary>
+		public static DownloadRequestDelegate RequestDelegate = null;
+
 		/// <summary>
 		/// 自定义的证书认证实例
 		/// </summary>
-		public static CertificateHandler CertificateHandlerInstance;
+		public static CertificateHandler CertificateHandlerInstance = null;
 
 		/// <summary>
 		/// 启用断点续传功能文件的最小字节数
@@ -32,14 +42,6 @@ namespace YooAsset
 		/// </summary>
 		public static List<long> ClearFileResponseCodes { set; get; }
 
-		/// <summary>
-		/// 自定义下载请求
-		/// </summary>
-		/// <param name="requestDelegate"></param>
-		public static void SetRequestDelegate(DownloadRequestDelegate requestDelegate)
-		{
-			DownloadRequestUtil.SetRequestDelegate(requestDelegate);
-		}
 
 		/// <summary>
 		/// 更新所有下载器
@@ -75,7 +77,11 @@ namespace YooAsset
 			}
 			_downloaderDic.Clear();
 			_removeList.Clear();
+			
+			RequestDelegate = null;
+			CertificateHandlerInstance = null;
 			BreakpointResumeFileSize = int.MaxValue;
+			ClearFileResponseCodes.Clear();
 		}
 
 
@@ -110,6 +116,18 @@ namespace YooAsset
 			}
 		}
 
+		/// <summary>
+		/// 创建一个新的网络请求
+		/// </summary>
+		public static UnityWebRequest NewRequest(string requestURL)
+		{
+			if (RequestDelegate != null)
+				return RequestDelegate.Invoke(requestURL);
+
+			var request = new UnityWebRequest(requestURL, UnityWebRequest.kHttpVerbGET);
+			return request;
+		}
+
 		/// <summary>
 		/// 获取下载器的总数
 		/// </summary>