php - 从 Web 服务器获取 JSON 数组到 iOS 的后台队列

Question

我正在执行后台队列以从 Web 服务器上的 MySQL 表中获取值。这是我用来获取 JSON 数组的 PHP 代码:

$id = $_GET['id'];

$arr = array();

$rs = mysql_query("SELECT * FROM tbcoordenadas where titulo='$id'");
while ($obj = mysql_fetch_assoc($rs)){
$arr[] = $obj['procedencia'];
}
echo json_encode($arr);

这是 iOS 部分从互联网获取 JSON 数组的代码:

   - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control
    {
        NSLog(@"annotation taped TITLE %@",[[view annotation] title  ]      ) ;



        //URL definition where php file is hosted
        dispatch_queue_t backgroundQueue = dispatch_queue_create("com.mycompany.myqueue", 0);

        dispatch_async(backgroundQueue, ^{


            NSMutableString *ms = [[NSMutableString alloc] initWithString:@"http://mujercanariasigloxxi.appgestion.eu/app_php_files/comprobartipo.php?id="];
            // URL request
            NSString *tipo=[[view annotation] title];

            [ms appendString:tipo];
            NSLog(@"TIPO ES AQUI %@", tipo);
            NSURLRequest *request1 = [NSURLRequest requestWithURL:[NSURL URLWithString:ms]];
            //URL connection to the internet
            //  NSURLConnection *connection=[[NSURLConnection alloc]initWithRequest:request delegate:self];

            [NSURLConnection sendAsynchronousRequest:request1
                                               queue:[NSOperationQueue mainQueue]
                                   completionHandler:
             ^(NSURLResponse *response, NSData *data1, NSError *connectionError)
             {
                 if (data1)
                 {
                     NSArray *array = [NSJSONSerialization JSONObjectWithData:data1 options:0 error:nil];

                     dispatch_async(dispatch_get_main_queue(), ^
                                    {
                                        // Update your label

                                        NSLog(@"PROCEDENCIA DESDE INTERNET %@", [array objectAtIndex:0]);

                                    });
                 }
                 else
                 {
                     // Tell user there's no internet or data failed
                 }
             }];


            dispatch_async(dispatch_get_main_queue(), ^{



            });
        });   

    }

过了一会儿，我发现编译器光标仅到达以下行:

  NSLog(@"PROCEDENCIA DESDE INTERNET %@", [array objectAtIndex:0]);

如果数组至少有两个对象。通常情况下，查询结果应该只得到一个对象。稍后将不可能获得两个对象，查询只会产生一个。

Answer 1

您的代码过于复杂。如果您使用的是 sendAsynchronousRequest，则不需要第一个 dispatch_async。此外，由于完成处理程序是在主队列上调用的，因此也不需要其他 dispatch_async 调用。在没有这些的情况下尝试一下，看看是否有帮助。

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control {
    NSLog(@"annotation taped TITLE %@",[[view annotation] title  ]);
    NSMutableString *ms = [[NSMutableString alloc] initWithString:@"http://mujercanariasigloxxi.appgestion.eu/app_php_files/comprobartipo.php?id="];
    NSString *tipo=[[view annotation] title];
    [ms appendString:tipo];
    NSLog(@"TIPO ES AQUI %@", tipo);
    NSURLRequest *request1 = [NSURLRequest requestWithURL:[NSURL URLWithString:ms]];

    [NSURLConnection sendAsynchronousRequest:request1 queue:[NSOperationQueue mainQueue] completionHandler: ^(NSURLResponse *response, NSData *data1, NSError *connectionError) {
        if (data1) {
            NSArray *array = [NSJSONSerialization JSONObjectWithData:data1 options:0 error:nil];
            NSLog(@"PROCEDENCIA DESDE INTERNET %@", [array objectAtIndex:0]);

        }else{
            // Tell user there's no internet or data failed
        }
    }];
}

编辑后:

这是我在测试中使用的实际代码。看看它是否适合您。

- (void)viewDidLoad {
    [super viewDidLoad];

    NSMutableString *ms = [[NSMutableString alloc] initWithString:@"http://mujercanariasigloxxi.appgestion.eu/app_php_files/comprobartipo.php?id="];
    NSString *tipo=@"ORIFLAME";
    NSString *tipo2 = @"centro1";
    [ms appendString:tipo];
    //[ms appendString:tipo2];
    NSLog(@"TIPO ES AQUI %@", tipo);
    NSURLRequest *request1 = [NSURLRequest requestWithURL:[NSURL URLWithString:ms]];

    [NSURLConnection sendAsynchronousRequest:request1 queue:[NSOperationQueue mainQueue] completionHandler: ^(NSURLResponse *response, NSData *data1, NSError *connectionError) {
        if (data1) {
            NSArray *array = [NSJSONSerialization JSONObjectWithData:data1 options:0 error:nil];
            NSLog(@"PROCEDENCIA DESDE INTERNET %@", array);

        }else{
            NSLog(@"no data");
        }
    }];
}