I'm creating an app which connects to server and sends some text.
If network (both wifi or 3g) is there, it will immediately send the text to server.
But if there is no network, it keeps on polling for server connection every 5 minutes.
All this part is working fine.
But when using iPhone 4 device, i want the app to check for server connection even when app goes into background. So, when app goes to background and when network comes back, it must be able to send the text to server.
How can I achieve it? I've seen some apps where they say that the app will upload photos to server even in background. How will they do it?
I suggest you read this article from Apple carefully, especially the Completing a Finite Length Task in the Background section.
http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/BackgroundExecution/BackgroundExecution.html
Something to clarify:
Once your app is in the background and is frozen by the OS, there would be no way for your app by it self to wake up and re-connect to the internet.
However, according to the article above from Apple, you can call this beginBackgroundTaskWithExpirationHandler method from your app's delegate to apply for additional time when put in the background, which is to say, though your app cannot wake up by it self when in background, it can, when in the background and not frozen, try to apply for additional time to finish its lengthy task.
Hope it helps.
There is a trick that I think flayvr is using.
If you download and use the app, you will see that they require you to enable your location.
And why is that?
because they want like you to do something in the background even when the app is terminated (they creating an album out of your newly captured photos), and how do they do that?
They use the significant location change, where when someone is traveling some significant distance (something like 500m) each app that registered for significant location change will get awaken for a limited amount of time to perform some quick task and will be terminated in a few seconds.
So your app can register to that event also and when the event of significant location change fired you will be able to send the text to server (quickly).
Hope that helps.
Until now you can do that on iOS7 with Background Fetch.
Take a look at this article.
However you only have up to 30s to get the task done.
According to the article above, there's also another solution called Background transfer service.
If more time is required though, then the Background Transfer Service
API can be used
Create a new project in Xcode and you will see there are bunch of new methods auto generated in app delegate file. like applicationDidEnterBackground, applicationWillEnterForeground etc.
read the description you have to call your thread to upload data on server here.
Related
After iOS 3.2, Apple allowed us to keep running our application in background mode. Using the same concept, in my application I have downloading functionality implemented which runs over in background mode.
The problem is that whenever I force quit my app manually, (Double tap on home button > long tap on app icon > tap on cross button of app) as per Apple specifications. I am not able to track that event in code, hence I am unable to track my downloading data.
Because of that, my data is being lost. So how to track this and track/save data before it gets force quitted.
Reference: AppDelegate Protocol
As far as I know, there is no way to handle that event, since it kills the whole process immediately.
You will need to save your data periodically or just leave it like it is. User killing apps, should be aware of that he is killing apps.
track each 'chunk of data' as you receive it and you write it to disk. that way you don't have to rely on a shutdown event
Thats how ASI and AFN do it and thats how you could also manually do it using NSURLConnection directly.
On startup, see if and how much of the data you already have in the file. Again ASI and AFN make this really easy!
I want to update some data to my application. Consider the application is in the background state, it is neither Voip or Music or GPS. Is it possible to update/send data to the application which is in background?
NOTE: I dont want to notify the user so that the application becomes active.
Can anyone help me ??
The answer is yes and no.
Apple does allow you app to complete a lengthy process in the background. But if you does not fall in the Voip, music or GPS category then you can't run in background.
If for example you want to send some data to a server, which could take some time, then you can mark that process to back executed until it is finished (or 10min. have passed).
You will find some about Executing a Finite-Length Task in the Background
There is not way to run timers or any thing like that in the backgroud, you can only finish a task you started before the app is backgrounded.
The alert which is displayed is an inbuilt functionality. You can't do anything for that. If a notification is fired from the server and application is in background then the alert will be displayed.
I have done a lot of search in past for this stuff.
I have done this in one of my work. this is what i did.
when application enter : - (void)applicationDidEnterBackground:(UIApplication *)application
I send data to server using ASIHTTPRequest with property :
[request setShouldContinueWhenAppEntersBackground:YES];
But after finished, i didn't do anymore connection or data manipulation. So, only the connection is running at background and not your app. you can't do much after the connection finish.
As #rckoenes was mentioned, you may not execute task too long.
If you would like to update server data while your app is running in the background mode, the application should be active at that time. It can only be active if it uses "music, or voip, or location tracking", otherwise the app will be paused in background mode.
One way to avoid this is to develop your application, and to set it to use, for example, «location tracking». This will allow it to meet the requirements for active background process and you will be able to update server data.
Unfortunately, I do not know whether the app can pass app store approval with this set-up.
However, if you are interested in this solution, you can find an example here.
I need that my app will send some data to server every six hours for example. Purpose is that it will send request to server even when app in background. As I know only thinks GPS, Music, Push Notifications work on background. Also, as I know UIApplication method beginBackgroundTaskWithExpirationHandler: works not for a long time after app goes on background. Guys, anybody have idea how to implement this? Thanks a lot!
It's simply not possible within the limits of the current iOS SDK. The only kind of apps that can update their content regularly from the background are Newsstand apps and for them, the interval is 24 hours AFAIK and the entire updating process is largely triggered by Apple.
Unless your app falls into one of the categories you mention, the short answer is you can't. The only exception is for Newsstand apps.
But: what data would you be sending to the server if your app isn't running? If you send data to the server when something happens then the server will always be up-to-date. If the user isn't running the app then, by definition, nothing has happened and the server is still "in sync" with the client. (Yes, this potentially makes the server harder to code.)
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 need to write an application, that every 10 minutes it should be awaken from suspended mode, get user location via gps and send this information to the server by network.
Depending on the response it should return to the suspended mode or show local notification to the user.
Is there a way to do this on iOS 4?
I've tried different approaches, but the only working for me was to start monitoring user location in backgroind and declare the application as location background application. In that case it worked in background and has a network connection. But this approach takes a lot of power and not accepted cause application should work 24/7.
May be there is a way to write some daemon that should work in background and wake my application every 10 minutes?
Apparently, Pastebot tried to do something similar with the 'audio' multitasking declaration (by playing a silent audiofile) and got rejected.. UNTIL they actually presented a option to the user to pick which audiofile they wanted to play. It's in the appstore now. :)
In this case: What is your reason for not wanting to use the location updates? If battery-usage is a concern, you can use the 'significant location changes only' option, after which you can temporarily change to a more accurate option.
This isn't possible outside of the method you have already tried.
The iPhone background task API will allow you to run a location service in the background.
There is no way to write daemons for the iPhone without jailbreaking, and that is not something I'm able/prepared to help you with.
App store friendly: use new APIs in iOS4, which allows u to make use of GPS location
Anti App store: create a daemon by adding a specific plist file to System/Library/LaunchDaemons/ and put ur app under Applications/. this approach requires a jailbroken iPhone however...
detailed information plz google the following keywords: daemon, multitask, background, etc...
cheers, Lloyd