Question

我的应用需要在后台跟踪用户位置，但无法发送“获取”请求。当应用程序到达前台时，会立即发送http请求。我正在使用RestKit来处理所有网络请求，然后我跟着this tutorial设置了我的后台位置服务。在我的applicationDidEnterBackground

中

-(void)applicationDidEnterBackground:(UIApplication *)application
{
    self.bgLocationManager = [[CLLocationManager alloc] init];
    self.bgLocationManager.delegate = self;
    [self.bgLocationManager startMonitoringSignificantLocationChanges];
    NSLog(@"Entered Background");
}

我在applicationDidBecomeActive委托中停止监视有意义的位置变更

这是我的locationManager委托，我接受新的更新位置并发送到我的服务器

-(void) locationManager:(CLLocationManager *)manager 
    didUpdateToLocation:(CLLocation *)newLocation 
           fromLocation:(CLLocation *)oldLocation
{
    NSLog(@"I am in the background");
    bgTask = [[UIApplication sharedApplication]
                beginBackgroundTaskWithExpirationHandler:
                ^{
                      [[UIApplication sharedApplication] endBackgroundTask:bgTask];
                 }];
                 // ANY CODE WE PUT HERE IS OUR BACKGROUND TASK

    NSString *currentLatitude = [[NSString alloc]
                                  initWithFormat:@"%g",
                                  newLocation.coordinate.latitude];
    NSString *currentLongitude = [[NSString alloc]
                                   initWithFormat:@"%g",
                                   newLocation.coordinate.longitude];
    NSString *webToken = [[NSUserDefaults standardUserDefaults] stringForKey:@"userWebToken"];
    NSLog(@"I am in the bgTask, my lat %@", currentLatitude);

    NSDictionary *queryParams;
    queryParams = [NSDictionary dictionaryWithObjectsAndKeys:webToken, @"auth_token",  currentLongitude, @"lng", currentLatitude, @"lat", nil];
    RKRequest* request = [[RKClient sharedClient] post:@"/api/locations/background_update" params:queryParams delegate:self];
    //default is RKRequestBackgroundPolicyNone
    request.backgroundPolicy = RKRequestBackgroundPolicyContinue;

    // AFTER ALL THE UPDATES, close the task

    if (bgTask != UIBackgroundTaskInvalid)
    {
        [[UIApplication sharedApplication] endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }
}

网络请求按计划运行，但不会在后台调用。我还需要其他步骤吗？在我的info.plist中，我有必需的背景模式键和位置服务作为值。

修改

我也提到了this past SO answer。我通过在didUpdateToLocation调用中放置日志来运行一些测试并且它们都被调用但是没有发送'get'请求。相反，当我最终将应用程序启动到前台时，它会发送所有构建的网络请求（超过10个）。

编辑（2）我在我的请求中添加了RKRequestBackgroundPolicyContinue，但它没有改变我的结果。（正如您在restkit的后台上传/下载中看到的那样here）。我看到Restkit初始化主机但未能发送请求，直到应用程序变为活动状态。

ANSWER

RestKit必须做一些在后台禁止的事情。使用NSURLRequest非常有效。

NSMutableURLRequest * urlRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.example.com/api/locations/background_update"]];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[urlRequest setHTTPMethod:@"POST"];
[urlRequest setHTTPBody:jsonData];

NSHTTPURLResponse  *response = nil;
[NSURLConnection sendSynchronousRequest:urlRequest
                      returningResponse:&response
                                  error:&error];

可以使用同步请求，因为没有UI可以破坏后台任务

Answer 1

重新创建原始建议作为答案

您是否尝试使用库存同步NSURLConnection替换您的restKit调用？ - dklt Sep 20

Answer 2

我使用与您完全相同的代码，它在RestKit中适用于我。我可以使它工作的唯一方法是创建一个同步请求（无论如何在这个上下文中异步执行它没有多大意义！）。请检查此代码，并告知我们是否有效：

// REMEMBER. We are running in the background if this is being executed.
// We can't assume normal network access.
// bgTask is defined as an instance variable of type UIBackgroundTaskIdentifier

// Note that the expiration handler block simply ends the task. It is important that we always
// end tasks that we have started.

_bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:
           ^{
               [[UIApplication sharedApplication] endBackgroundTask:_bgTask];
           }];

// ANY CODE WE PUT HERE IS OUR BACKGROUND TASK

// For example, I can do a series of SYNCHRONOUS network methods (we're in the background, there is
// no UI to block so synchronous is the correct approach here).

NSNumber *latNumber = [NSNumber numberWithDouble:location.coordinate.latitude];
NSNumber *lngNumber = [NSNumber numberWithDouble:location.coordinate.longitude];
NSNumber *accuracyNumber = [NSNumber numberWithDouble:location.horizontalAccuracy];
NSDictionary *params = [NSDictionary dictionaryWithKeysAndObjects:@"lat",latNumber,@"lng",lngNumber,@"accuracy",accuracyNumber, nil];
RKURL *URL = [RKURL URLWithBaseURL:[NSURL URLWithString:SERVER_URL] resourcePath:@"/user/location/update" queryParameters:params];
RKRequest *request = [RKRequest requestWithURL:URL];
request.method = RKRequestMethodGET;
NSLog(@"Sending location to the server");
RKResponse *response = [request sendSynchronously];
if (response.isFailure)
    NSLog(@"Unable to send background location, failure: %@", response.failureErrorDescription);
else {
    NSError *error = nil;
    NSDictionary *parsedBody = [response parsedBody:&error];
    if (YES == [[parsedBody objectForKey:@"result"] boolValue]){
        NSLog(@"Background location sent to server");
    }
    else {
        //Something went bad
        NSLog(@"Failed to send background location");
    }
}
// AFTER ALL THE UPDATES, close the task

if (_bgTask != UIBackgroundTaskInvalid)
{
    [[UIApplication sharedApplication] endBackgroundTask:_bgTask];
    _bgTask = UIBackgroundTaskInvalid;
}

我几乎可以肯定，为您的RKClient请求生成的新线程会在调用后自动终止。

Answer 3

当您的应用程序在后台运行时，您可以在输入后台之前完成您启动的HTTP请求，但无法发起新请求。您只能在后台（voip，报亭）发起certain network operations。

iOS后台位置不发送http请求

3 个答案: