问题
I am trying to implement the suggestions given in this post.
Unfortunately the steps are not clear to me. I tried implementing those suggestions, but the backgroundTimeRemaining continues to decrease even after I start and stop locationServices. This is how I developed it:
- (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);
}
Does anyone have a suggestion on what might be wrong in my code? Both initTimer and checkUpdates are being called, but only during for the background execution time (+- 10 Mins). I want the app to update the location every n minutes "forever".
My app's UIBackgroundModes is set to location.
UPDATE:
I am now resetting the timer on didUpdateToLocation and didFailWithError. But still the backgroundTimeRemaining keeps decreasing:
- (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.
});
}
I am also invalidating the timer:
- (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);
}
回答1:
To anyone else having a nightmare of a time trying to figure this one out, I have a simple solution.
- Study the example from raywenderlich.com. The sample code works perfectly, but unfortunately there's no timer during background location. This will run indefinitely.
Add timer by using this code snippet:
-(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]; }Just don't forget to add "App registers for location updates" in info.plist.
回答2:
After some days trying all possible solutions I was finally able to make it work. Here is what was wrong in my solution:
- I need to setup 2 UIBackgroundTaskIdentifiers, one for the timer, and another one for the locationManager
On my solution, just add:
UIApplication *app = [UIApplication sharedApplication];
bgTask2 = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask2];
bgTask2 = UIBackgroundTaskInvalid; }];
self.locationManager.delegate = self;
[self.locationManager startUpdatingLocation];
回答3:
Once you're in the background you can only have 10 minutes of additional time. There is no way to extend that. You should use the location background services instead.
回答4:
Working Code(Entire Stepwise Code) Modified scurioni's code
Step 1
- Go to project -> Capabilities -> Background Modes -> select Location updates.
- Go to Project -> Info -> add a key NSLocationAlwaysUsageDescription with an optional string.
Step 2
Add this code to AppDelegate.m
@interface AppDelegate ()<CLLocationManagerDelegate>
@property (strong, nonatomic) CLLocationManager *locationManager;
@property (strong, nonatomic) NSTimer *timer;
@end
Step 3 Add This Code in to applicationDidEnterBackground method in AppDelegate.m
- (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
}
来源：https://stackoverflow.com/questions/10235203/getting-user-location-every-n-minutes-after-app-goes-to-background