I need to save a big file, sometime it takes a very long time to finish, user might just close the application. I am wondering whether the iPhone SDK could take over the unfinished big task.
Appears iPhone's own mail system could do background send. I prepared a email, click send, then close the mail app immediately. In home page, after several seconds, I heard a sound and the email was delivered.
You're out of luck. Only Apple's own apps are allowed to operate in the background. But I think your app gets some time to finish up when the user closes the app.
You can't run the app in the background as PEZ says. However you could spin off a thread to perform the task and then at least the user can get on with doing other things in your application.
If I remember correctly, your app gets 5 seconds between the user pressing the home button and the iPhone OS killing it if you're not done.
Related
Is it possible to put your app in the background, and have a counter that once expires, wakes up the app and have the app does some action? I know it's basic, but I just cant seem to have it work. Where do I put this counter + action? Under app did enter background?
Thanks for the help.
I don't think that this works in general:
You are allowed only to run in the background for specific tasks:
Apple doc tells which tasks that are:
One of that tasks is receiving GPS messages.
As long as you have GPS enabled and your app configured that it uses GPS for background, your app stays alive in the background.
If you disable GPS some time later it will suspend, and not wake up till the user activates it.
So to realize your problem you have to stay active in the background (e.g by reading GPS).
You can start the timer in AppDelegate:applicationDidEnterBackground or similar
If you need more time to shutdown, you explicitly can request for more time, there is one method for that. I dont know what happens if you request more at regulary intervals
I'm thinking in making an app that send e-mails without showing the native iOS mail app. For that I'd be using sksmtpmessage framework.
I'd like as well to keep sending the e-mail when the app goes in background. According to this thread, it would be doable.
I know that Apple limits a few tasks to be done is the background (Audio, VoIP and location). Then my question is, would Apple reject an app using sksmtpmessage framework to send an e-mail from the background?
Cheers :)
If you're just "completing a task" (i.e. the user loads the app to send some e-mails, then quits before they're all sent), you're fine - that's what the Task Completion multitasking mode is for. If you want to run constantly in the background sending e-mail, then it'll almost certainly be a reject (if they spot it) - this isn't something they envisage being done on the iPhone.
From the app docs : An application can call the beginBackgroundTaskWithExpirationHandler: method to ask the system for extra time to complete some long-running task in the background. If the request is granted, and if the application goes into the background while the task is in progress, the system lets the application run for an additional amount of time instead of suspending it. (The backgroundTimeRemaining property of the UIApplication object contains the amount of time the application has to run.)
You can do preceding in time, because iOS 4 gives you a 10 mins of time for task completion after you exit an app.
Is it possible to keep a socket connection alive in background, to be able to push new data and alert users at all times?
The answer to this question is a definitive yes. If you are in the background state, then you can keep a connection open and process messages from a server.
Unfortunately the complexity here is that you don't have a lot of control over the state your application is in:
foreground - The user has tapped your icon and the app is running with the UI visible.
suspended - The user was previously running your app in the foreground, but suspended it by hitting the home button or receiving a call. Basically your app is 'freeze dried' and will remain inactive until it is resumed by the user (starting where it left off) or it is terminated by the OS (see below).
background - The app was previously running in the foreground but has moved to the background state as a result of something the user has done. Normally your app will move to the suspended state in this case, but there are things you can do as the developer to prevent the instant 'freeze dry' and go into the background instead (see below). Your app will also be in the background state if it is woken up for a significant change event.
terminated - Your app has been unloaded from memory and the next time it starts will be from scratch. This is what happens when you double click the home button and then tap the x next to your app icon. It moves the app from the suspended state into the terminated state. This will also happen if the OS decides it needs room for more recently running apps and your app has been suspended for a long time.
So obviously the trick here is how do I stay in the background state as a long as possible. There are a couple of ways to do this:
Beg for more time - You can get up to 10 minutes of additional background processing when your app is closed if you ask for it.
Use UIBackgroundMode - You can declare youself a voip, audio or location app by adding the corresponding UIBackgroundMode value to the pList. There are special requirements for these types of apps which you can check out here.
So these approaches are not without their own problems (getting approved on the store being one of them) and as such I tend to agree with the other answers that using push notifications is probably your best approach for notifying your users. With the notification improvements in iOS5 this is going to be the best user experience going forward.
You can keep a socket connection alive (or do whatever else you want) in the background for about 15 minutes after your app closes. There are also more specialized background processing modes (specifically, audio, voip, and location) which Apple supports if your app fits into one of their supported categories. See here.
If you want to keep sending the user notifications indefinitely, you want to use the Apple Push Notification Service. This allows your app to continue to receive notifications when it's not running, and it conserves resources since there's only one connection to the APN service at a time.
You can definitely alert users with local and push notifications.
And as far as I know, you can keep a connection open only for limited time.
Look here for more details.
When iPhone application go to applicationWillResignActive mode, I need to download the data from specific site continuously(Using Timer) and if any data receive from that site should push the UILocalNotification. But if App has enter into Background, Downloading functions is not calling. Exactly i want as Mail app.
You can't do that unless you're a VoIP app or a GPS app.
For other types of app, the closest you can do is request the 10 minute long task completion mode. That'll give you ten minutes of running whatever you want in the background, after which the system kills your app.
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