如何在ios8中保持在后台连续获取位置？

Question

如何在iOS8中保持后台连续定位，同时又要尽量省电？有人能给我一些建议吗？

Answer 1

在您的项目设置中，选择Target并转到Capabilities，打开后台模式，勾选location updates和background fetch。这将在你的项目plist中添加背景模式。

现在，为了即使在后台也能获得连续的位置更新，可以在AppDelegate的applicationDidEnterBackground:方法中添加以下代码。这段代码每次都会杀死后台任务，然后重新启动它。因此，即使应用程序在后台，您也会收到后台位置更新。

- (void)applicationDidEnterBackground:(UIApplication *)application {
    if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)]) { //Check if our iOS version supports multitasking I.E iOS 4
        if ([[UIDevice currentDevice] isMultitaskingSupported]) { //Check if device supports mulitasking
            UIApplication *application = [UIApplication sharedApplication]; //Get the shared application instance

            __block UIBackgroundTaskIdentifier background_task; //Create a task object

            background_task = [application beginBackgroundTaskWithExpirationHandler: ^{
                [application endBackgroundTask:background_task]; //Tell the system that we are done with the tasks
                background_task = UIBackgroundTaskInvalid; //Set the task to be invalid
                //System will be shutting down the app at any point in time now
            }];
        }
    }
}

现在，为了延长设备电池寿命，您可以使用locationManager:didUpdateLocations:方法，因为它仅在位置根据所需精度更改时才会调用。

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    CLLocation *location = [locations lastObject];
    if (location != nil) {
        strLatitude  = [NSString stringWithFormat:@"%f", location.coordinate.latitude];
        strLongitude = [NSString stringWithFormat:@"%f", location.coordinate.longitude];
    }
}

Answer 2

Found some Solution here

研究Ray Wenderlich中的示例。示例代码运行得很好。

你可以通过使用这个代码片段来添加计时器，这可能会减少一点电池消耗：

-(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];
}