Is it possible that my iphone application will run in background state and after some time interval it will start another program or application from my iphone.
Suppose, I want to start the camera preview after 10 minute later that will be handled from my iphone. So, my application will run in background state and it will start the camera view after 10 minutes.
Is it possible ???
The only way to start other applications is to use the url schemes exposed by the other app. If it does not expose such scheme, you won't be able to start it.
What about scheduling such thing when you're in the background, you can register for timed local notifications that will show a popup to the user when the time has been elapsed. If the user accepts the popup, your application will get focus and CPU so you can launch also other apps.
There is another option, to get some seconds of CPU in every 10 minutes. It is called VoIP services and you can register for it in the project settings, then it'll call a callback in your app delegate when the OS decides to grant you some CPU.
Study "local notifications" and "url schemes", these are the technologies you need.
Specifically on whether your app can do anything while in the background state, recommend watching the 2010 WWDC video "Session 105 - Adopting Multitasking on iPhone OS, Part 1" : https://developer.apple.com/itunes/?destination=adc.apple.com.4092349126.04109539109.4144345587?i=1907522673
TL;DR: you can only finish up tasks upon entering the background. MrTJ is right about using a timed local notification, and you can also investigate Apple Push Notifications too, if a bit more work and outside the scope of your original ask.
Related
I'am developing an application that keep a WebService informed for device location each 5minute (for exemple) :
So when the application leave the foreground execution and enter background I have to lunch a timer who
1 - Update the device location
2 - Send the location to a web service
How can I perform this action ? Or do you know any code exemple that I can follow to achieve this design ?
Thank you for your help !
Doesn't look like anyone gave you a solid answer, so allow me.
There is no iOS approved way of running a 5 minute (or any minute) timer in the background (unless your app is VOIP or music). What you CAN do is register your app as requiring location services in the background (edit the info.plist and add a key Required Background Modes and then add a value App registers for location updates. What this means is your locationManager:didUpdateToLocation:fromLocation: method and corresponding region monitoring/SLC methods will fire on location change, but Timers will not work at all.
The reason why is that timers require a run loop (a thread executing code) to be running and must piggy-back on that thread, but when the app is in the background even when executing code from the LocationManager, the run loop that executes the code almost always finishes before your timer would go off.
Hope this helps!
you cannot do this (on iOS).
(unless your app requests permissions that are meant for Navigation apps)
Hello #Aladdin Gallas,
I have developed a simple application that supports background location updates for iOS and Android in Xamarin.
The app pushes a new location every 2 seconds (you can change it to 5 minutes if you want to).
There is a feature I haven't been able to add; it is to keep the service up when the user closes the app (for iPhone). Other than that, as long as the app is open, even if the phone is locked, the service keeps running.
You can take a look at the application as a reference if it helps.
GitHub Repo
Is it possible to get a notification (that launches the app) when the network gets available?What I want is my application to update its contents as soon the internet gets available.The only way I can think of is to send a push from the server once is a while (may be once a day)and that tell the user it might be a good idea to get yourself synchronized.
This is currently impossible if your background task scope is limited to that feature. The only way you could do this is if you had some other legitimate reason to become a background app (aka VOIP or GPS) and run reachability checks every X minutes, and then post a UILocalNotification that allows the user optionally open the app (you cannot programmatically open your app yourself).
I have an iphone app that has a 30second process that does some network IO. Basically, while the app is in the background, i want this process to run every hour (actually once a day, but if it fails i want it to re-run in an hours time).
With the background features of ios 4, is this possible? If so, how? What are the limitations that i'll come up against?
Thanks so much!
Take a look at Apple's documentation about running code in the background.
http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/BackgroundExecution/BackgroundExecution.html
There are few different ways of approaching backgrounded tasks. The only apps that can have fully backgrounded processes are "audio", "voip" and "location" apps, and this needs to be declared in the Info.plist.
If your app is not of this type, you'll probably find it difficult to do what you want easily. There are methods which allow you to keep your app alive in the background for a finite period of time (also at that link), but eventually your app will be shut down.
Local Notifications will only prompt the user to open the app - do you really want to have an alert pop-up on the phone every 30 seconds?
I was making some kind of similar research, have a look at this SO answer in case you didn't manage to find it before. Applications like DataMan or Data Usage must have some sort of periodic code execution in the background, so I'm not 100% convinced that what you're asking for is impossible..
I believe that Using Local notifications will help....
check following....
http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/IPhoneOSClientImp/IPhoneOSClientImp.html#//apple_ref/doc/uid/TP40008194-CH103-SW1
An application can create and schedule a local notification, and the operating system then delivers it at the schedule date and time. If it delivers it when the application is not active in the foreground, it displays an alert, badges the application icon, or plays a sound—whatever is specified in the UILocalNotification object. If the application is running in the foreground, there is no alert, badging, or sound; instead, the application:didReceiveLocalNotification: method is called if the delegate implements it.
The delegate can inspect the properties of the notification and, if the notification includes custom data in its userInfo dictionary, it can access that data and process it accordingly. On the other hand, if the local notification only badges the application icon, and the user in response launches the application, the application:didFinishLaunchingWithOptions: method is invoked, but no UILocalNotification object is included in the options dictionary.
I can't seem to find a clear answer to this-- I'm spec'ing out an iPhone app that I'd like to have live in the background and notify the user at certain periods throughout the day. So the user would launch the app in the morning and then continue to use their phone, then every few hours the app would pop open a notification dialog.
Will my app ever be shut down (automatically) by the OS? Or will it just live forever, notifying user when it needs to?
thanks,
Eric
Basically there are three kinds of running in the background on iOS 4:
Running in the background to "finish" stuff (e.g. upload a posting or a picture, finish processing something etc.). You ask the OS to grant you extra time after the user switches to another app, and it will tell you how much time you got. You can't run in the background for an indefinite time.
Running in the background to do specific stuff: VoIP, tracking location (e.g. for GPS navigation), or playing audio. You can only do the stuff that you told the OS you would do in the background.
Local notifications (UILocalNotification). From your description, this is what you're looking for. You're not actually running, you just schedule notifications, and when it's time to notify the user, they'll be notified and can go to your app. If you need to notify the user dynamically (i.e. you don't know ahead at what times they need to be notified and it's not location or VoIP triggered), you might want to look into push notifications.
Apple has a good overview here:
https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_ui_to_run_in_the_background/about_the_background_execution_sequence
Ever since the first beta came out I’ve been trying to find out if “real” multitasking is possible — i.e. can you put a program in the background and have it hang on to a network connection indefinitely?
I’m thinking about IM or IRC apps, for example. I’ve compiled an app myself on iOS 4, and without changing a thing it appeared to stay running in the background, but for all I know it was just suspended to memory.
The docs say the best you can do is request up to 10 minutes, but in the developer presentation they showed off Skype sitting in the background and then notifying the user that a call was coming in. Does anyone know for sure how this all works?
It appears the answer is no. The API for Skype is a very special case, called the "voip" mode, and requires special behavior, such as marking the socket in use for VoIP.
You can receive alarm notifications in the background (such as time passed). The amount of time you are in the background running state is severely limited by the OS.
Android's background model is complete and in many ways much nicer.
Apple has a guide named "Supporting Multitasking In Your Applications" which you should be able to locate.
Apple's iOS 4 developer docs outline this all very clearly.
When your app is closed or switched away from, it is almost immediately "suspended", meaning the OS freezes the app's state. When the user switches back to your app, your code keeps running just where it kept off. You don't need to add any code to your app to do this, just compile it against OS 4.
The above is true in most cases. There are two reasons the "suspended" model may not apply:
1) If the device starts to run low on memory, the OS will start terminating suspended apps that haven't been switched to in a while, without warning. This is why it's in your best interest for your app to remember it's state as well, so if your app is terminated, then re-opened, the user doesn't really notice because it still returns to right where they left off.
2) Your app uses one of the "background" APIs. These are for audio playback, VoIP services, or location services. In this case, your app is allowed to continue running in the background but only has access to those APIs. Additionally, your app can designate certain long-running tasks as "background tasks" that need to be completed before the app is suspended or terminated, like uploading pictures to Flickr or rendering a video, etc.
The "background task" method doesn't cover pinging servers indefinitely, as there is a time limit for the task, after which it will be forcibly halted. Apps that need that sort of functionality are expected to implement push notifications, just as before.
That should clear this up. All in all I think it's a pretty elegant solution to multitasking on a mobile device.
iOS 4 applications can either be running or suspended. The operating system will try to keep as many requested applications as possible in memory, while all other applications are suspended.
Applications that run in the background can access features such as navigation, audio, and VOIP (but NOT instant messaging). So it looks like you might be out of luck.
-- PC World Multitasking on Apples iPhone 4
It is possible for apps to request background time. Read the docs. I would say it iOS is "controlled multitasking".
You can create a long running background task, I believe these can include networking features. Just have to set the background task flag on the work block.
https://developer.apple.com/iphone/library/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html
the OS can limit exactly how much time you get though... it will tell you when your time is up giving you a chance to cleanup nicely.
iOS 4 has "real" multitasking to some extend. There are two things to consider:
The UI event loop is single tasking. So only the front app executes on the UI event loop. Not a big deal: detach your main code form the UI event loop (maybe you need to redesign your app).
The OS "may" terminate your app if some criteria are met (e.g. low memory).
Currently one of these criteria is that execution time is limited to 10 minutes (real time not cpu time). However I expect this to change and see better criteria for background app termination (I hope to).
Apart from this you can have timers (event loops) in background.
There is no real multitasking in iOS 4.2 even. because apps will only be allowed to finish the task related to states..for small interval of time and then it will be in suspended state.. If you will set background task for long interval of time then... it will behave unexpectedly like no method will be called when you will try to run the app from anywhere..
You may be interested in this blog post that outlines how "multitasking" works in systems such as iPhone OS 4 and Android.
in fact u can do this, although it's not allowed by Apple. u gotta set up a toolchain in ur mac and use some unofficial SDK...
check http://code.google.com/p/iphone-backgrounder/ for more information
You should use the Push Notifications framework for the feature set you are creating!