1

将数据发布到 json Web 服务后，我需要提醒用户数据是否保存成功。我对此没有任何问题，但是在日志中得到响应“数据保存成功”后，视图需要很长时间（几乎 40-50 秒）才能显示警报视图。一旦我在几秒钟内得到响应，谁能帮我获得警报视图？这就是我所做的

NSURL *url = [NSURL URLWithString:@"some url"];
        NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
        NSData *requestData = [NSJSONSerialization dataWithJSONObject:dictionary options:kNilOptions error:&error];
        [request setHTTPMethod:@"POST"];
        [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
        [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
        [request setValue:[NSString stringWithFormat:@"%d", [requestData length]] forHTTPHeaderField:@"Content-Length"];
        [request setHTTPBody: requestData];
        NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
        [connection start];
        [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
            if(error || !data)
            {
                NSLog(@"JSON Data not posted!");
                [activity stopAnimating];
                UIAlertView *alertMessage = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Data not saved" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                [alertMessage show];
            }
            else
            {
                [activity startAnimating];
                NSLog(@"JSON data posted! :)");
                NSError *error = Nil;
                NSJSONSerialization *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];

                NSLog(@"Response is %@", jsonObject);

                NSString *code = [jsonObject valueForKey:@"Code"];
                NSLog(@"Code value = %@", code);
                if([code intValue] == 0)
                {
                    [activity stopAnimating];
                    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data updated!" message:@"Entered data above has been saved in the database successfully." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                    [alert show];
                }
                else
                {
                    [activity stopAnimating];
                    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data not saved" message:@"" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil];
                    [alert show];
                }

            }

        }];
    }
4

2 回答 2

5

我认为您正在从单独的线程调用警报视图代码。所有 UI 元素都需要从主线程处理。

在您的情况下，您应该更改为以下内容，

[activity performSelectorOnMainThread:@selector(stopAnimating) withObject:nil waitUntilDone:NO];
[alert performSelectorOnMainThread:@selector(show) withObject:nil waitUntilDone:NO];

或者你可以用 GCD 做到这一点，

dispatch_async(dispatch_get_main_queue(), ^{
    [activity stopAnimating];
    UIAlertView *alertMessage = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Data not saved" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alertMessage show];
});

希望有帮助！

于 2013-11-14T07:09:33.503 回答
1

您应该在主线程的块内进行所有 UI 交互。只需使用以下代码

dispatch_async(dispatch_get_main_queue(), ^{
   [activity stopAnimating];
                    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data updated!" message:@"Entered data above has been saved in the database successfully." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                    [alert show];
});
于 2013-11-14T07:10:16.450 回答