How to keep apple watch app running in background.
I build a timer, but every time screen dims and I wake up the app it resets the timer. How to avoid this?
I don't think you're supposed to.
Apple specifically say:
Do not use background execution modes for a technology. Watch apps are considered foreground apps because they run only while the user interacts with one of their interfaces. As a result, the corresponding WatchKit extension cannot take advantage of most background execution modes to perform tasks.
You might want to check elapsed time on wakeup instead.
Related
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.
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 hope to run an app in background on ios4
I know
Apple allows only certain types of apps to run in the background, like navigation and audio and VOIP apps. But even those are limited to only the necessary tasks.
Is it possible I register the app as one kind of VoIP, Audio or GPS apps to keep it run in background?
Welcome any comment
You can't "run" an app in the background; you can only run a task in the background. The tasks are
Continue Playing Audio
Maintain VoIP Connection
Update Location (GPS)
Some Finite Task (such as uploading a file)
I haven't developed for iOS so there might be something I'm missing. Read more at Executing Code in the Background. As of iOS 4, developers don't have the ability to implement true multitasking. Correct me if I'm wrong in any of this.
Not in general, no. You could register a VoIP or GPS session and abuse its callbacks for certain tasks, but I doubt the App Store review process would take kindly to it.
What do you need to do in the background that isn't covered by task completion or the audio/VoIP/GPS background modes? it might be possible to use another paradigm and still get the cake.
In order to run the app continuously in the background on the 3GS and iPhone4 on OS4.1
is it simply enough to call BeginBackgroundTask in the DidEnterBackground callback and then
NOT call EndBackgroundTask ie to leave it running. I understand this will run the battery
down but that is ok as my users will be running on power.
If this is not the way to do it , can someone say how to keep the app running (not suspended)
Thanks
You cannot keep the app running on the background.
You can declare some tasks that the system will run in background.
According to the Apple documentation:
Support for some types of
background execution must be declared
in advance by the application that
uses them. An application does this by
including the UIBackgroundModes key in
its Info.plist file. This key
identifies which background tasks your
application supports. Its value is an
array that contains one or more
strings with the following values:
audio - The application plays audible
content to the user while in the
background. location - The application
keeps users informed of their
location, even while running in the
background. voip - The application
provides the ability for the user to
make phone calls using an Internet
connection. Each of the preceding
values lets the system know that your
application should be woken up at
appropriate times to respond to
relevant events. For example, an
application that begins playing music
and then moves to the background still
needs execution time to fill the audio
output buffers. Including the audio
key tells the system frameworks that
they should continue playing and make
the necessary callbacks to the
application at appropriate intervals.
If the application did not include
this key, any audio being played by
the application would stop when the
application moved to the background.
In addition to the preceding keys, iOS
provides two other ways to do work in
the background:
Applications can ask the system for
extra time to complete a given task.
Applications can schedule local
notifications to be delivered at a
predetermined time. For more
information about how to initiate
background tasks from your code, see
“Initiating Background Tasks.”
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!