xamarin.ios - iOS8:backgroundSessionConfiguration 已弃用

Question

在 iOS8 发布之前，我下载了 iOS8 SDK 以观察我的应用程序将如何工作。有时我的应用程序需要从服务器下载数据，我为此使用 NSUrlSession。现在，当应用程序准备下载 session 时，会出现下一个警告:
+backgroundSessionConfiguration: is deprecated. Please use +backgroundSessionConfigurationWithIdentifier: instead .

之后，我的应用程序崩溃，出现下一个异常:

Unable to cast object of type 'MonoTouch.Foundation.NSUrlSessionTask' (Objective-C type: '__NSCFBackgroundDownloadTask') to type 'MonoTouch.Foundation.NSUrlSessionDownloadTask'.
Additional information:
    Selector: URLSession:downloadTask:didFinishDownloadingToURL:
    Method: Microsoft.Synchronization.ClientServices.NSUrlDownloadDelegate:DidFinishDownloading (MonoTouch.Foundation.NSUrlSession,MonoTouch.Foundation.NSUrlSessionDownloadTask,MonoTouch.Foundation.NSUrl)

创建 NSUrlSession 的代码:

NSUrlSessionConfiguration sessionConfiguration = NSUrlSessionConfiguration.BackgroundSessionConfiguration(urlSessioinId);
NSUrlDownloadDelegate downloadDelegate = new NSUrlDownloadDelegate();
NSUrlSession downloadSession = NSUrlSession.FromConfiguration(sessionConfiguration, downloadDelegate, new NSOperationQueue());

谢谢你的帮助!

Answer 1

我使用以下方法来解决 Objective-C 中的这个错误:

NSURLSessionConfiguration *sessionConfig;

if ([[[UIDevice currentDevice] systemVersion] floatValue] >=8.0f)
{
    sessionConfig =[NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"downloads"];
}
else
{
    sessionConfig = [NSURLSessionConfiguration backgroundSessionConfiguration:@"downloads"];
}