I'm writing an app for a client where the users will enter data during the day, then at a given point at night (say, at midnight) the user's data for that day should upload to the server.
Therefore I need to schedule a method to run on my app at midnight, even if the app is in the background. This method will then sync the collected data with the server and download any changes.
In order to achieve this, I imagine I need to set the app to always run in the background (i.e. longer than 10 minutes) then schedule the function to run after a specific time. Do I do this by using performSelector: withDelay:? Or do I need something more robust because the app will be in the background?
Thanks guys!
You might check out UILocalNotifications. You could schedule that event to happen and then set a badge icon to let the user know it processed something (or not).
Info on these HERE
I don't think your app or what you are trying to do is qualified for Apple's requirement for long running background task. Check out the "Implementing long-running background tasks" section of this doc from Apple.
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Say I want to perform a background task, like upload some data, at a given date and time after the user has quit my app. So the app is killed, but I still want to run a task later on.
Is that possible? Is there a background mode to do that?
There is no background mode that awakens your application at a given time. You can use silent push notifications, but in that case you will need to have a backend that send push notifications to your app.
Also you can try using Background fetch mode, basically when the system wakes up your app you can check if the current date is the actual date that you need to execute your code.
You can utilise the Background App Refresh capability of iOS to achieve this.
Whilst you cannot specify an exact time to perform your background task, you can set a desired minimum interval to execute the task.
It's worth noting however that a user can disable this capability on both an app and device-wide level, so you should ensure that there is alternative logic to handle this situation.
I'm writing a iOS/Swift application which reads data from a REST service each X minutes and updates the UI accordingly.
Now I would like that when the app is put in the background, a task keeps being invoked at X minutes intervals reading from the REST service and, in case the data just read satisfies a given condition, show a notification prompting the user to bring the app back to the foreground.
In my searches I've read that during applicationDidEnterBackground event, I should start a task with beginBackgroundTaskWithExpirationHandler.
The problem is that, if I've understood correctly, this allows a maximum of 10/15 minutes after which the app is terminated if the task is not stopped with endBackgroundUpdateTask, while I want the task to keep polling the service indefinitely (at least until the user disable it from the app's settings)
My question is:
How is this kind of functionality performed normally? Do some common solutions or best practices exist for the solution of such a problem?
Use iOS Background Fetch feature where you can specify minimum background fetch interval. But actual interval between successive invocation of your code will be determined by iOS framework. For details checkout this link: http://code.tutsplus.com/tutorials/ios-7-sdk-working-with-background-fetch--mobile-20520
I use this approach in my app and I think it is a preferred way of doing.
You can use a local notification that can be presented from the background in case your condition is met.
Correct, iOS will eventually shut down the background process, you can't enforce continuous background activity. Use the backgroundTimeRemaining property to check how much time your application has left and try to handle it as gracefully as possible by calling endBackgroundTask so that iOS does not force kill your app.
As a solution, you could think about using remote notifications with with content-available : YES, which runs the didReceiveRemoteNotification
Have a look at the Parse.com Their local datastore is an abstraction for what you are trying to acheive.
By the way, is it really necessary to refresh in the background. If call is relatively quick, there is no need to refresh until the user open's the app. Background processes like that, using the net can be quite battery consuming when the user are not on a Wifi. So consider the use case carefully!
I am trying to get the location updates in iOS application and also want to save it every 15 mins no matter application is in foreground or background. So definitely the AppDelegate is the class where I need to configure these.
I read about the background tasks, but it wasn't giving proper idea of the process. Can someone provide me with good source or link?
You must check location at least every 3 minutes and create a backgroundTask using beginBackgroundTaskWithExpirationHandler
more info in here
When iPhone app is in background state or when app is minimized, I want to monitor the duration of time the app is in background and on every regular interval like every 24hrs need to get updates from web server and write the modifications in my local database.
This monitor cycle will repeat as long as app is in background. Is this kind of task is possible in iPhone applications ? Could any body help me how can I perform these tasks when app is in background state ?
beginBackgroundTaskWithExpirationHandler: is the API to make the app in background for long tasks but how long will this support.
Background tasks are killed after 10 minutes time, so to answer your question: No, it's not without faking some kind of long term event handling through a significant location's update, and even then, you have no control over when exactly the events are sent. On the other hand, using APNS to alert the user to a change has the possibility of being ignored, but comes with regularity.
I have a background app with a UIBackgroundMode of location.
I would like my app to additionally contact a server every few or several hours to see if there is some new data for it (because using apple notification push would notify the user and that is not desirable).
Polling is something I would never use on any other OS, but with iOS they don't leave you much choice if there is certain functionality you would like to try to achieve.
If the polling interval is quite lengthy such as a few or several hours between polls, and the polling activity itself only lasts several seconds then the usual knee-jerk reaction about it draining battery life is greatly diminished.
Would a repeating NSTimer fire when an app is in background mode? If not is there another type of timer or mechanism available?
If it's just to check for new content, and not really time sensitive, you COULD use the significantChanges background location method...but if the user stayed fairly immobile it'd rarely/never fire. I would probably also add the update check in applicationWillEnterForeground to be more sure
No, that's not allowed. You should have a look at Push Notifications and find a server side solution.