提问



我正在努力实施这篇文章中给出的建议。


不幸的是,我不清楚这些步骤。我尝试实现这些建议,但是即使在我启动和停止locationServices之后,backgroundTimeRemaining仍然继续减少。这就是我开发它的方式:


- (void)applicationDidEnterBackground:(UIApplication *)application {

    UIApplication*    app = [UIApplication sharedApplication];

    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];

    // Start the long-running task and return immediately.
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // Do the work associated with the task.
        self.timer = nil;
        [self initTimer];

    });
}


initTimer:


- (void)initTimer {

    // Create the location manager if this object does not
    // already have one.
    if (nil == self.locationManager)
        self.locationManager = [**CLLocationManager alloc] init];

    self.locationManager.delegate = self;
    [self.locationManager startMonitoringSignificantLocationChanges];

    if (self.timer == nil) {
        self.timer = [NSTimer scheduledTimerWithTimeInterval:0.3
                                              target:self
                                            selector:@selector(checkUpdates:)
                                            userInfo:nil
                                             repeats:YES];
    }
}


checkUpdates:


- (void)checkUpdates:(NSTimer *)timer{
    UIApplication*    app = [UIApplication sharedApplication];
    double remaining = app.backgroundTimeRemaining;
    if(remaining < 580.0) {
        [self.locationManager startUpdatingLocation]; 
        [self.locationManager stopUpdatingLocation]; 
        [self.locationManager startMonitoringSignificantLocationChanges];
    }
    DbgLog(@"Reminaing %f", app.backgroundTimeRemaining);
}


有没有人对我的代码中的错误有什么建议?正在调用initTimer和checkUpdates,但仅限于后台执行时间(+ - 10分钟)。我希望应用程序每隔n分钟永远更新位置。


我的应用程序的UIBackgroundModes设置为位置。


更新:


我现在正在重置didUpdateToLocation和didFailWithError上的计时器。但是backgroundTimeRemaining仍在不断减少:


- (void)locationManager:(CLLocationManager *)manager 
didUpdateToLocation:(CLLocation *)newLocation 
       fromLocation:(CLLocation *)oldLocation {

NSLog(@"Did Update Location = %f / %f", [newLocation coordinate].latitude, [newLocation coordinate].longitude);

UIApplication*    app = [UIApplication sharedApplication];

bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
    [app endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];

// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    // Do the work associated with the task.

    [self initTimer];

});
}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {

[self.locationManager stopUpdatingLocation]; 
UIApplication*    app = [UIApplication sharedApplication];

bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
    [app endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];

// Start the long-running task and return immediately.
[self initTimer];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    // Do the work associated with the task.

});

}


我也使计时器无效:


- (void)checkUpdates:(NSTimer *)timer{
UIApplication*    app = [UIApplication sharedApplication];
double remaining = app.backgroundTimeRemaining;
if(remaining < 580.0 && remaining > 570.0) {
    [self.timer invalidate];
    self.timer = nil;
    [self.locationManager startUpdatingLocation]; 
    [self.locationManager stopUpdatingLocation]; 
}
DbgLog(@"*************************Checking for updates!!!!!!!!!!! Reminaing %f", app.backgroundTimeRemaining);
}

最佳参考


对于其他任何有过噩梦的人试图解决这个问题,我有一个简单的解决方案。



  1. 研究raywenderlich.com的示例。示例代码完美无缺,但不幸的是,在后台定位期间没有计时器。这将无限期运行。

  2. 使用此代码段添加计时器:[11]


    -(void)applicationDidEnterBackground {
      [self.locationManager stopUpdatingLocation];
    
      UIApplication* app = [UIApplication sharedApplication];
    
      bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
      }];
    
      self.timer = [NSTimer scheduledTimerWithTimeInterval:intervalBackgroundUpdate
                                                    target:self.locationManager
                                                  selector:@selector(startUpdatingLocation)
                                                  userInfo:nil
                                                   repeats:YES];
    }
    

  3. 不要忘记在info.plist中添加应用寄存器以进行位置更新。


其它参考1


经过几天尝试所有可能的解决方案,我终于能够使它工作。这是我的解决方案中的错误:



  • 我需要设置 2 UIBackgroundTaskIdentifiers,一个用于计时器,另一个用于locationManager



在我的解决方案上,只需添加:


UIApplication *app = [UIApplication sharedApplication];

bgTask2 = [app beginBackgroundTaskWithExpirationHandler:^{ 
[app endBackgroundTask:bgTask2]; 
bgTask2 = UIBackgroundTaskInvalid; }];

self.locationManager.delegate = self; 
[self.locationManager startUpdatingLocation]; 

其它参考2


一旦你在后台,你只能有10分钟的额外时间。没有办法扩展它。你应该使用位置后台服务。

其它参考3


工作代码(整个逐步代码)
修改了scurioni的代码


第1步



  • 转到项目 - >功能 - >背景模式 - >选择位置更新。

  • 转到项目 - >信息 - >使用可选字符串添加密钥NSLocationAlwaysUsageDescription。



第2步


将此代码添加到AppDelegate.m


@interface AppDelegate ()<CLLocationManagerDelegate>
@property (strong, nonatomic) CLLocationManager *locationManager;
@property (strong, nonatomic) NSTimer *timer;
@end


第3步
将此代码添加到 AppDelegate.m 中的 applicationDidEnterBackground 方法


    - (void)applicationDidEnterBackground:(UIApplication *)application {
        UIApplication *app = [UIApplication sharedApplication];
        __block UIBackgroundTaskIdentifier bgTaskId =
        [app beginBackgroundTaskWithExpirationHandler:^{
            [app endBackgroundTask:bgTaskId];
            bgTaskId = UIBackgroundTaskInvalid;
        }];

        dispatch_async( dispatch_get_main_queue(), ^{
            self.timer = nil;
            [self initTimer];
            [app endBackgroundTask:bgTaskId];
            bgTaskId = UIBackgroundTaskInvalid;
        });
    }

- (void)initTimer {
    if (nil == self.locationManager)
        self.locationManager = [**CLLocationManager alloc] init];

    self.locationManager.delegate = self;
    [self.locationManager requestAlwaysAuthorization];
    [self.locationManager startMonitoringSignificantLocationChanges];
    if (self.timer == nil) {
        self.timer = [NSTimer scheduledTimerWithTimeInterval:0.3
                                                      target:self
                                                    selector:@selector(checkUpdates:)
                                                    userInfo:nil
                                                     repeats:YES];
    }
}

- (void)checkUpdates:(NSTimer *)timer{
    UIApplication *app = [UIApplication sharedApplication];
    double remaining = app.backgroundTimeRemaining;
    if(remaining < 580.0) {
        [self.locationManager startUpdatingLocation];
        [self.locationManager stopUpdatingLocation];
        [self.locationManager startMonitoringSignificantLocationChanges];
    }
}

- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation {
    NSLog(@"Did Update Location = %f / %f", [newLocation coordinate].latitude, [newLocation coordinate].longitude);
    [self updateLocationWithLatitude:[newLocation coordinate].latitude andLongitude:[newLocation coordinate].longitude];
    UIApplication*    app = [UIApplication sharedApplication];
    __block UIBackgroundTaskIdentifier bgTask =
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self initTimer];
    });
}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
    [self.locationManager stopUpdatingLocation];
    UIApplication *app = [UIApplication sharedApplication];
    __block UIBackgroundTaskIdentifier bgTask =
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
    [self initTimer];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // Do the work associated with the task
    });
}

-(void)updateLocationWithLatitude:(CLLocationDegrees)latitude
                     andLongitude:(CLLocationDegrees)longitude{
//Here you can update your web service or back end with new latitude and longitude
}