在 NSURLSession 内部使用时，UIAlertView 花费的时间太长

Question

我正在使用 NSURLSession 从我的服务器获取一些信息。获取数据后，我将其显示在 UIAlertView 中，但显示时间太长。我用 NSLog 打印数据，它几乎立即打印出来……那么发生了什么？方法 dataTaskWithRequest 不是异步的吗？为什么弹出提醒视图需要这么长时间？

NSURLSession *session;
session = [NSURLSession sharedSession];
NSURL * url = [NSURL URLWithString:[DRESSABLE_IP stringByAppendingString:@"index.php"]];
NSMutableURLRequest * urlRequest = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:CONNECTION_CACHEPOLICY  timeoutInterval:CONNECTION_TIMEOUT];
[urlRequest setHTTPMethod:@"POST"];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:urlRequest 
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSString *total = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        [[[UIAlertView alloc] initWithTitle:@"Title" message:total delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil] show];
 }];

Answer 1

所有UIactivity必须在主队列中完成。

NSURLSession *session;
session = [NSURLSession sharedSession];
NSURL * url = [NSURL URLWithString:[DRESSABLE_IP stringByAppendingString:@"index.php"]];
NSMutableURLRequest * urlRequest = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:CONNECTION_CACHEPOLICY  timeoutInterval:CONNECTION_TIMEOUT];
[urlRequest setHTTPMethod:@"POST"];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:urlRequest 
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSString *total = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
dispatch_async(dispatch_get_main_queue(),^{
        [[[UIAlertView alloc] initWithTitle:@"Title" message:total delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil] show];
});
 }];

在 NSURLSession 内部使用时，UIAlertView 花费的时间太长

UIAlertView takes too long when using inside NSURLSession

uialertview

ios

nsurlsession

ios8

nsurlsessiondatatask