在应用程序进入后台后，每隔n分钟获取用户位置

Question

我正在努力实施这篇文章中给出的建议。

不幸的是，我不清楚步骤。我尝试实施这些建议，但后台时间剩余继续减少，即使我开始和停止位置服务。我是这样开发它的：

- (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];
    }
}

检查更新：

- (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);
}

有人对我的代码中可能出现的错误有什么建议吗？正在调用initTimer和checkUpdates，但仅在后台执行时间（-10分钟）期间调用。我希望应用程序“永远”每隔n分钟更新一次位置。

我的应用程序的UIBackgroundModes设置为location。

更新：

我现在正在重置didUpdateToLocation和didFailWithError上的计时器。但剩余的背景时间仍在减少：

- (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.

});

}

我还使计时器无效：

- (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);
}

Answer 1

一旦你在后台，你只能有10分钟的额外时间。没有办法扩大这一点。您应该改用位置后台服务。

Answer 2

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

• 我需要设置2个UIBackground任务标识符，一个用于定时器，另一个用于locationManager

在我的解决方案中，只需添加：

UIApplication *app = [UIApplication sharedApplication];

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

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

Answer 3

对于任何一个正在经历噩梦的人来说，我有一个简单的解决方案。

>

学习raywenderlich的例子。通用域名格式。示例代码工作得很好，但不幸的是，在后台定位期间没有计时器。这将无限期地运行

使用以下代码段添加计时器：

-(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];
}

别忘了在info.plist.中添加“位置更新应用注册”