I'm using URLSession to download a .zip file when the first view appears, and it works fine.
The problem is that if the user's device sleeps after a duration (I believe 15/75 seconds are the options in settings) or by tilting their wrist etc - the download fails and the user has to retry when they open the app back up.
Other than warning the user to interact with the device during download, or changing their settings (neither ideal), is there anything I can do? It's not a huge file, around 10mb but poor networks could take a while.
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I am working on Location Tracking Application. This application continuously send location even in background. I am using SLC property.
I am also using silent push trick for location tracking. Logic of Silent push:
Check AppIconbadge number and perform the action according to AppIconbadge number. I have a timer which check AppIconbadge at every 10 seconds.
Now this is the case:
Device is on SLC and put the app in background and turn off the device. While you switch back to On this device it is still reporting on SLC while Ping (Silent Push) is not working.
I have started the timer when app get SLC trigger. But its not working.
Can you help?
You can't do it.
The way iOS achieves great battery life and reduces RAM usage makes this kind of thing impossible.
Your only real possibility is to have your server send occasional push notifications to the device, and have your app on the device respond with its location. This is how Find My Phone and Find My Friends both work. The idea is to improve battery life by doing as much as possible on a server, which has mains power and virtually unlimited RAM, instead of on the phone which only has a battery and might need all it's RAM to play a 3D game
Basically the CPU is not running at all most of the time, so it can't schedule stuff to run periodically, and you can't rely on there being enough RAM available to run your app so it also can't be running all the time even if the CPU is powered on.
According to the WWDC 2013 keynote, push notifications are much more powerful on iOS 7, so you should look that up (I haven't looked into it myself, just saw the keynote.
I am planning to add a feature where users on Wi-Fi can downloading files sized between 150mb and 1gb so that they can use the app offline.
The download manger will take a time between 2 mins and A few hours to get the content depending on the size of file and the Wi-Fi connection speed.
Many users have an auto lock which will activate after a period of inactivity. When the device is locked the network connection is killed to preserve battery life (Im fairly sure this is correct as of iOS5?). This would be frustrating for users as it would frequently suspend their downloads unless they kept the device active.
To get round this I am considering 2 options:
Set idleTimerDisabled = YES while the app is downloading to prevent the screen locking. I don't think this is a good use of the properly since the documentation seems to suggest this should only be set for apps. Also it would unnecessarily keep the screen on, which is not good for battery.
Use the background task completion API. Its its a bit vague how long this will last for, it might not be long enough for the users, but it could be better than nothing.
Are either or both of theses options viable?
I have developed an application. My application takes feedback from users. When network is not available, then that data is saved in local db. But, once the network is available, it will sync automatically with the central database.
But, I have some problem here. If I save database & send my application to background, once the network is available, it has to automatically do this syncing with the central database. How to do that?
I am using Reachability class to check network availability.
At the present time there is no way to have your app "wake up" when the network becomes available. If the user quit your app without a network connection, you cannot do anything until they voluntarily open your app.
However, you can prompt them to do so using UILocalNotification. If your app is being quit and you have some data waiting to be uploaded, you can schedule a notification to fire in 4 hours (or whatever amount of time makes sense).
If the user opens the app before the notification time and you are able to upload the data, you can cancel the notification and no one will ever know it was scheduled.
If the user does not open the app, the notification will appear, and say something like, "You have data on your phone that you have not uploaded in a while. Connect to the Internet and launch MyAwesomeApp to sync your data."
You cannot do it on iPhone. Your app ceases to exist in a few seconds (once the app moves to the background).
I believe its 5 seconds for all apps, 10 mins for some apps that have requested for more background time.
PS: Unless, you mark your app as a navigation or a music app, which can stay on in the background, theoretically, forever. But I doubt if a feedback app can get approved on the appstore with such permissions.
Keep an additional column in your saved database which marks successful uploading of your data to your server. Set this when the data is written, but not yet uploaded. When it's successfully uploaded, clear the value. You can check this value when your app comes to the foreground, and have it upload any data that hasn't had this column cleared. While your app is running, you can set a timer for an appropriate interval to recheck reachability and if successful, attempt an upload. Only clear your flag when the data is successfully written, and make sure your server doesn't try to process a partial upload (think of someone trying to do this on a subway or train, moving in and out of connectivity).
I have a problem with working in background mode ... I have an application for iPhone and it download some information from internet (for example RSS Feed) when my application enter to the background it stops download. When I call from background function that open connection and begin to download it stops, like something happens with my internet connection like it closed. Con somebody answer me can I continue downloading or starts a new one in background mode or I can't. I read This but I can't understand if I can do work except
* 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.
in background mode.
Thank you for answer ...
First of all, that Apple document you mentioned has exactly what you need.
Second, read this post, Download data in background with iOS4
Third, to make things clear, what you need is not audio/location/voip, what you need is the Completing a Finite Length Task in the Background section, which was discussed and was presented with a short code sample in that Apple document.
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.