Ios AFN网络连接失败，响应为。状态代码0

我想通过谷歌地理编码（EX URL=）从纬度和经度获取地址

所以我想通过AFNetworking从该页面获取JSON。 下面是我的代码：

IBAction)reLocation:(UIButton*)sender
{
    if(sender.tag==1)
    {
        NSArray *gpsValue = [self getGPS];

    float lat = [[gpsValue objectAtIndex:0] floatValue];
    float lon = [[gpsValue objectAtIndex:1] floatValue];

    NSString *string = [NSString stringWithFormat:@"%@%@,%@&sensor=true_or_false",GEOCODING_URL,[NSString stringWithFormat:@"%f", lat],[NSString stringWithFormat:@"%f",lon]]; //        NSString *str = [NSString stringWithFormat:@"%f", myFloat];
    NSLog(string);
    NSURL *url = [NSURL URLWithString:string];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
    operation.responseSerializer = [AFJSONResponseSerializer serializer];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
    {
        NSLog(@"AFNetworking success");
        NSDictionary *location = (NSDictionary *)responseObject;

        // 3
        self.title = @"JSON Retrieved";
        //[self.tableView reloadData];
        NSLog(responseObject);

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        NSLog(@"AFNetworking failure");
        switch (operation.response.statusCode) {
            case 400:
                // Do stuff
                NSLog(@"error 400");
                break;
            default:
                NSLog([NSString stringWithFormat:@"%ld",(long)operation.response.statusCode]);
                break;
        }
        // 4
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather"
                                                            message:[error localizedDescription]
                                                           delegate:nil
                                                  cancelButtonTitle:@"Ok"
                                                  otherButtonTitles:nil];
        [alertView show];
    }];

    // 5
    [operation start];


}}

但当我点击我的按钮时，afnetworking总是失败，日志显示状态代码为0

我还得到了我放进去的url日志 我已经检查过url并没有问题（它以工作顺序显示json）

我用模拟器调试

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是否有遗漏？

有时模拟器连接丢失，请重新启动模拟器。