I need to get the time when an iPhone switches off due to battery or other reasons. But, I need to save when the phone switches off time and when the phone switches on time using objective-c code. How do I do this?
You cannot detect phone switch off. But what you can do is to add an observer via Notification Center to monitor battery level changes.
UIDeviceBatteryStateDidChangeNotification
You need to create a logic to check current battery level and then save the time stamp.
Related
My app needs the device location with an accuracy of about 10 meters. If the app is launched, it usually takes e.g. 10 sec to get the required accuracy. This delay is OK. However when the app is „in use“ (see below), the delay should be less, e.g. 1 sec.
The problem is the following:
When the user switches off the display, the app transits from the active state to the background state (and the delegate methods applicationWillResignActive and applicationDidEnterBackground are called).
Normally, location updates are not done in background. So, next time the app transits from background to active state (delegate methods applicationWillEnterForeground and applicationDidBecomeActive are called), the location manager needs again e.g. 10 sec to reach the required accuracy. This delay in unfortunately not OK.
To avoid it, the app could do location updates in the background. This works fine.
The disadvantage is that these background location updates continue, even if the app is no longer used, because the user pressed the home button and switched to another app. This is disturbing at least for 2 reasons: The GPS hardware is unnecessarily active and uses power, and the user is notified that my app is using the device location although this is no longer required.
My question thus is:
Is it possible to determine if another app becomes active?
If so, background location updates could be switched off.
Is it possible to determine if another app becomes active?
No, your app only knows if it's in background or in foreground handling delegate events. Know if user opened another app or is in the home screen is not possible.
These background location updates continue, even if the app is no longer used, because the user pressed the home button and switched to another app.
I think you're right. You could start a timer when application goes in background and update localization only for an estabilished period (one minute?). Then, at the end of timer count save last localization coordinates. Timer is used to avoid unnecessary updates, then if user doesn't open again your app after a reasonable time, maybe it's because he's using other apps or he locked the device.
When the app comes to the foreground again, if timer is still active you're good. Otherwise show last localization saved and show a small "banner" to advise user that localization could not be accurated for the first 10 seconds (until when required accuracy has been reached)
Is there any way to show a particular type(some important) of push notification for some 5-10 seconds on the iOS device screen when app is in background.
No, the time is fixed.
You cannot customize it - a push-notification should be a short message that in the best case makes the user tap it and open the app. There is actually not really a need for a longer time. Keep it short, simple and interesting and the user will react accordingly anyway. A longer time should not really make any difference other than people getting annoyed because your messages are always staying on top, blocking other messages and wasting screen space.
With the M7 chip in the latest iOS devices one can get programmatically notified as the user goes from stationary to running, walking, etc using CMMotionActivityManager. Stava and Runkeeper have both used this to auto-pause GPS polling (shut off the GPS antenna) when it detects the user isn't moving via the M7, and then re-enable GPS updates once they are moving again. It is able to do this while the app is in the background state, which is the key here.
The issue I run into while duplicating this functionality is that if I turn off GPS updates while my app is in the background I stop receiving activity updates, and can no longer detect when the user moves again via the M7 to turn the GPS back on.
If I leave the GPS running the whole time I'll continue to get movement updates from Core Motion the entire time the app is in the background.
I'm assuming they aren't playing white-noise or some other cheap trick to stay active. How did they go about this?
RunKeeper actually does use the audio trick to stay awake. If you open up the app package and check their Info.plist you will see that it registers for the background audio mode. This is how they pull off periodic audio notifications of your distance, speed, and pace. It is also how they stay awake during your run while minimizing battery drain.
If you noticed that the Location Services icon (the triangle in the status bar) disappears completely while using RunKeeper then they definitely are not using any type of location tracking to accomplish background execution. Even activating geo-fences and significant location change monitoring would cause the Location Services icon to appear.
They also aren't using the M7 to stay awake because it doesn't work that way. An update from the M7-related CoreMotion APIs will not wake up your app from sleep. When they app does wake up they would be able to query the Motion Activity and Step history and maybe try to compute something, but I doubt it would be all that accurate.
Finally you should note that the Auto-pause APIs were introduced in iOS 6 before the release of the iPhone 5s and M7 chip. They are orthogonal concepts.
have you considered experimenting with
application:performFetchWithCompletionHandler:
in the app delegate? You can't control how often it is called, but depending on the app, it can be every ~15 minutes. You can then launch the CMMotionActivityManager from there to query M7 results.
It's not entirely clear what functionality you are trying to replicate, but the M7 chip records all of the activity, regardless of whether your app is running. So you can simply query in the background and update step totals or activity type totals.
What I noticed when you turn off GPS, app will not execute any code in background for iOS 7, app looks like in inactive state. So better while moving to background use startMonitoringSignificantLocationChanges and also get updates from your location manager. Means simultenoulsy use both service startUpdatingLocation on user state change and startMonitoringSignificantLocationChanges in Background.
So when user Turn on GPS, while you used startMonitoringSignificantLocationChanges your app will receive
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
Better check here in background itself what wrong with CoreMotion Framework. And try to restart it.
Because wihtout M7 chip device I am able to read Accelerometer reading in such case.
If your location manager is working in Active mode, to enable background mode you need to do this three steps:
Check that [Target / Capabilities / Background Modes / Location updates] is enabled.
[locationManager requestAlwaysAuthorization];
locationManager.allowsBackgroundLocationUpdates = YES;
First, check if you have set up the background behave of your app.
Go to target - capabilities section and check Background mode for location updates.
I am working on a app which need to check time after every minute when the app is in the background. I want to match current time with specific time, and if time matches then the app should show an alert (when app is in background).
You set a Local Notification and even the App is dead after going to background, the local notification will pop up. As in your example it will tell the user "Time to take your medicament" and if the user choose the "View Details" button, your app will be fired from the iOS
Another method how can you do this is to trick the ios (Apple :-) )
Apple allows you to stay in background without beeing killed if you do some specific tasks, such as Location
So what you can do is
in the info.plist add "Required background modes" and value Location
Info here http://developer.apple.com/library/ios/#documentation/general/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html
Than Set up a CLLocationManager for scanning the location and obey the Apples advice and make it not very accurate (battery life saving)
Setup a timer and in the timer routine check the location (that saves the apps life) and than do whatever you want to do ...
This should also work.
Dear fellow developers,
I am trying hard to find a solution for my problem regarfing CLLocationManager.
I use a CLLocationManager instance in my Application. If the user selects the Home button on the device or terminates the application I want the location services to stop.
Therefor I call [self.locationManager stopUpdatingLocation]; - But this somehow doesn't work. The application enters the background and the small location arrow in the upper right corner of the status bar don't disappear. Even if I add [self.locationManager release] or self.locationManager.delegate = nil; - the location tracking don't stop :-/
It only disappears if I go to my device settings and switch off location services for the app. Whenever I switch back to location service enabled I immediately get a purple colored arrow next to the switch toggle and the icon reappears in the status bar.
My question is how can I turn off location services when the app enters the background or is terminated?
Thanks a lot in advance and have a nice day :-)
Your location is disabled. The location service icon "meaning" has changed on iOS 5. Take a look at this question: https://apple.stackexchange.com/questions/27463/why-is-the-location-services-icon-always-present
I Quote the answer:
It's a new feature in ios 5 called "region Monitoring"
The reason it's active even if the app is closed is that this feature
runs in iOS 5 core and notifies all apps that are registered when they
have entered or left a specific geo-fence.
Reminders does that when you use a location based reminder.
Although the location icon appears at all time. This actually has very
minimal impact on the battery due to apple really optimizing this
feature by using cell and wifi mostly.
Your app is working ok. The system behaviour is the one who changed.
You do it the right way. When entering background, it's ok if some delegate methods are called for some seconds. That should stop.
Where do you stop the location updates ? Are you sure it is triggered ? If yes, are your delegate method called even if the visual indicators tell something else ?
Are you sure you don't trigger a method that reactivate the location update after you have stopped it (because for example you can receive some updates even after stopped).
For instance if you started monitoring a significant location change, then you should unsubscribe from it with the corresponding pair method. If you are using region enter, then until you unsubscribe, the system will notify your delegates.