Error in NSURLSessionDownloadTask

问题

I am trying to update the user's location on the backoffice even while the app is in backgound, so I trigger a location update calling the following php script:

-(void)locateUserAtLocation:(CLLocation*)location{
NSDictionary* dict=[self getCurrentAppAndUrlDictionary];
NSString* app=[dict objectForKey:@"app"];
float latitude=location.coordinate.latitude;
float longitude=location.coordinate.longitude;
NSString* language=[[NSLocale currentLocale] localeIdentifier];
NSString* nickName=[[NSUserDefaults standardUserDefaults] objectForKey:@"nickname"];
NSString* myUdid= [udid sharedUdid];
NSString *insertUrlString =[NSString stringWithFormat: @"http://www.miafoto.it/iPhone/inarrivo/taxi/insertUserNew.php?udid=%@&token=%@&nickname=%@&app=%@&language=%@&Latitude=%f&Longitude=%f&new=1",myUdid, token, nickName, app, language, latitude, longitude];
NSLog(@"url=%@", insertUrlString);

 NSURLSessionDownloadTask *insertTask = [[self backgroundSession] downloadTaskWithURL:    [NSURL URLWithString:insertUrlString]];
[insertTask resume];
}

but I get error: Invalid URL scheme for background downloads: (null). Valid schemes are http or http and no url is sent either in foreground or background. I searched on the web I found no hits addressing this issue. I also submitted the issue to the Apple support.

回答1:

You might have some reserved characters that prevent the NSURL object from instantiating correctly, i.e. URLWithString is probably returning nil.

NSString *insertUrlString =[NSString stringWithFormat: @"http://www.miafoto.it/iPhone/inarrivo/taxi/insertUserNew.php?udid=%@&token=%@&nickname=%@&app=%@&language=%@&Latitude=%f&Longitude=%f&new=1",myUdid, token, nickName, app, language, latitude, longitude];

You can confirm this by checking the NSURL:

NSURL *url = [NSURL URLWithString:insertUrlString];
NSAssert(url, @"problem instantiating NSURL: %@", insertUrlString);

Do any of those strings have spaces or other reserved characters in them? It's always safer to percent escape these values. Personally, I add my parameters to a dictionary, and then have a function that will percent escape the values, e.g.:

NSDictionary *parameters = @{@"udid"      : myUdid,
                             @"token"     : token,
                             @"nickname"  : nickName,
                             @"app"       : app,
                             @"language"  : language,
                             @"Latitude"  : @(latitude),
                             @"Longitude" : @(longitude),
                             @"new"       : @"1"};

NSString *insertUrlString = [NSString stringWithFormat: @"http://www.miafoto.it/iPhone/inarrivo/taxi/insertUserNew.php?%@", [self encodeParameters:parameters]];

NSURL *url = [NSURL URLWithString:insertUrlString];
NSAssert(url, @"problem instantiating NSURL: %@", insertUrlString);

where:

- (NSString *)encodeParameters:(NSDictionary *)parameters
{
    NSMutableArray *parameterArray = [NSMutableArray arrayWithCapacity:[parameters count]];

    for (NSString *key in parameters) {
        NSString *string;
        id value = parameters[key];

        if ([value isKindOfClass:[NSData class]]) {
            string = [[NSString alloc] initWithData:value encoding:NSUTF8StringEncoding];
        } else if ([value isKindOfClass:[NSString class]]) {
            string = value;
        } else if ([value isKindOfClass:[NSNumber class]]) {
            string = [value stringValue];
        } else {                         // if you want to handle other data types, add that here
            string = [value description];
        }
        [parameterArray addObject:[NSString stringWithFormat:@"%@=%@", key, [self percentEscapeString:string]]];
    }

    return [parameterArray componentsJoinedByString:@"&"];
}

- (NSString *)percentEscapeString:(NSString *)string
{
    NSString *result = CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                                                 (CFStringRef)string,
                                                                                 (CFStringRef)@" ",
                                                                                 (CFStringRef)@":/?@!$&'()*+,;=",
                                                                                 kCFStringEncodingUTF8));
    return [result stringByReplacingOccurrencesOfString:@" " withString:@"+"];
}

回答2:

Here is easier solution

 NSURL *url = [NSURL URLWithString: [[yourURLinString
 stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]
 stringByTrimmingCharactersInSet:[NSCharacterSet
 whitespaceAndNewlineCharacterSet]]];

Parse your string url this way and it should work.

来源：https://stackoverflow.com/questions/23630541/error-in-nsurlsessiondownloadtask

标签

xcode

ios7.1

nsurlsessiondownloadtask