I have an app that will run in the background but there is one case where I do not want that to happen, can I achieve this programmatically?
I know I can opt out by changing this plist value but what about at run time?
Add the variable UIApplicationExitsOnSuspend (Application does not run in background) to your applications plist and assign the value YES.
You can close the app by calling exit(0) in applicationDidEnterBackground.
You can't use exit(0) b/c apple does not allow you to close the app without user knowing it.
From Technical Q&A QA1561 How do I programmatically quit my iPhone application?.
There is no API provided for gracefully terminating an iPhone
application. Under the iPhone OS, the
user presses the Home button to close
applications. Should your application
have conditions in which it cannot
provide its intended function, the
recommended approach is to display an
alert for the user that indicates the
nature of the problem and possible
actions the user could take - turning
on WiFi, enabling Location Services,
etc. Allow the user to terminate the
application at their own discretion.
Calling exit() is discouraged, and not informing the user that the app is going to terminate is also discouraged. So you need to get the OS to kill your app (as it normally would do over a long enough period of operation) while simultaneously informing the user. One way of doing this, while using only legal APIs, is to dirty absolutely as many memory pages as possible (malloc and bzero), then call Safari with a URL to a hoggish website explaining why the app is going to quit. Safari will require enough memory to display the website that your app will be terminated by the OS, just as the user is being properly informed.
Sleeping until the OS kill timer kills your app will also kill your app, but this non-responsive delay will lock up the UI, which isn't a good user experience.
Related
Does anyone know if exit(0) is deprecated in iOS application? I know it is not a good decision to manually terminate the app, but does Apple ban the application if we use it in the code?
I got an app which was rejected because of a way of exit (via UIAlertView), doing an exit(5) when user click on the correct button.
I received that:
We found that your app includes a UI control for quitting the app.
This is not in compliance with the iOS Human Interface Guidelines, as
required by the App Store Review Guidelines.
Please refer to the attached screenshot/s for reference.
The iOS Human Interface Guidelines specify,
"Always Be Prepared to Stop iOS applications stop when people press
the Home button to open a different application or use a device
feature, such as the phone. In particular, people don’t tap an
application close button or select Quit from a menu. To provide a good
stopping experience, an iOS application should:
Save user data as soon as possible and as often as reasonable because an exit or terminate notification can arrive at any time.
Save the current state when stopping, at the finest level of detail possible so that people don’t lose their context when they start the
application again. For example, if your app displays scrolling data,
save the current scroll position."
It would be appropriate to remove any mechanisms for quitting your
app.
A "hidden" exit could be understood as a crash for the user, no?
No, Apple will not reject your app for using exit(0).
You are correct, it is not a great design choice, but it can be useful sometimes.
As Larme mentioned, if used incorrectly, it can be perceived as a crash and a crash will result in your app being rejected.
However, it can be very useful in applicationDidEnterBackground when (on a conditional basis ) you might want to force the app to start a fresh.
No, you must not call exit as your app SHOULD be rejected. This has been repeatedly discouraged by Apple and is known to cause serious bugs with iOS multitask switching. You should simply leave the user to use the home button themselves.
http://developer.apple.com/library/ios/#qa/qa1561/_index.html
"Additionally, data may not be saved, because -applicationWillTerminate: and similar UIApplicationDelegate methods will not be invoked if you call exit. If DURING DEVELOPMENT or TESTING it is necessary to terminate your application, the abort function, or assert macro is recommended."
2012-04-09
Updated to more strongly discourage the exit function, and include best practices for debugging.
2008-08-27
New document that discusses best practices for terminating an iOS application in code.
Straight from the iOS Human Interface Guidelines
http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/MobileHIG/UEBestPractices/UEBestPractices.html#//apple_ref/doc/uid/TP40006556-CH20-SW27
"Don’t Quit Programmatically
Never quit an iOS app programmatically because people tend to interpret this as a crash. However, if external circumstances prevent your app from functioning as intended, you need to tell your users about the situation and explain what they can do about it. Depending on how severe the app malfunction is, you have two choices.
Display an attractive screen that describes the problem and suggests a correction. A screen provides feedback that reassures users that there’s nothing wrong with your app. It puts users in control, letting them decide whether they want to take corrective action and continue using your app or press the Home button and open a different app
If only some of your app's features are unavailable, display either a screen or an alert when people use the feature. Display the alert only when people try to access the feature that isn’t functioning.
If Necessary, Display a License Agreement or Disclaimer
If you provide an end-user license agreement (or EULA) with your iOS app, the App Store displays it so that people can read it before they get your app.
If possible, avoid requiring users to indicate their agreement to your EULA when they first start your app. Without an agreement displayed, users can enjoy your app without delay. However, even though this is the preferred user experience, it might not be feasible in all cases. If you must display a license agreement within your app, do so in a way that harmonizes with your user interface and causes the least inconvenience to users.
If possible, provide a disclaimer within your app description or EULA. Users can then view the disclaimer in the App Store, and you can balance business requirements with user experience needs."
We don't want the user enter our app if the app is out-dated.
Is that is possible to quit a iOS app when we do some date check BEFORE the app launch?
Or it is possible to quit the application after the main view is loaded?
Before the app launches: no. The launch animation is already in progress when the OS calls main.
After some time (1-2 sec): yes. You can use one of
[[UIApplication sharedApplication] terminateWithSuccess];
exit(0);
abort();
assert(0);
pthread_kill(pthread_self());
so many ways, but neither will go through AppStpre - you're not supposed to close your app programmatically. You're supposed to notify the user via an UIAlertView about the outdated app and disable interaction with the app.
According to Apple you cannot exit(quit) your application through code. i.e if you use exit(0). Your application will be rejected for that. Although you can use exit(1) and delay the exit time of your application. Or you may like to use local notification which is quite handy.
Don’t Quit Programmatically
Never quit an iOS application programmatically because people tend to
interpret this as a crash. However, if external circumstances prevent
your application from functioning as intended, you need to tell your
users about the situation and explain what they can do about it.
Depending on how severe the application malfunction is, you have two
choices.
Display an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures users that
there’s nothing wrong with your application. It puts users in control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
If only some of your application's features are not working, display
either a screen or an alert when people activate the feature. Display
the alert only when people try to access the feature that isn’t
functioning.
Source
So here is the issue I am facing. Certain portions of the application I am building open some c network sockets that allow connections to various servers/services. However, if the application goes to sleep, these socket connections are lost, and error out when trying to reload them. So what I want to do is basically notify the user when the app launches again, that the application needs to be restarted. The main question is, can I present them with a button that will kill the app by using exit(0) without my app getting rejected?
Apple says that the user should be in control of when the app is killed, and in this case I see that they are, but I am not sure of Apple's opinion on this. Has anyone else used this? Have you been rejected for this? Thanks in advance for any advice!
EDIT:
Thank you everyone for your advice. I am trying to take everything into consideration, but because the app needs to be submitted ASAP, I just need to know, if we can not get another solution, if the above proposed solution, will get rejected or not.
Your application delegate receives notifications when significant events affect the life of the application. Rather than ask your user to recreate a session, you should attempt to discontinue network operations and then resume them at the appropriate times in the application's lifecycle automatically.
You can gracefully kill network sockets (amongst other things) in any number of places as the application prepares to exit or enter the background via callbacks in your application delegate:
applicationWillResignActive:
applicationWillEnterBackground:
applicationWillTerminate:
Potentially reconstruct sockets in:
applicationDidBecomeActive
applicationWillEnterForeground
Have you tried not allowing the app to run in the background? Then it will be killed whenever the user exits to the home screen. This might be a bit aggressive, but would solve the problem. From Apple's opting out of background execution:
"If you do not want your application to remain in the background when
it is quit, you can explicitly opt out of the background execution
model by adding the UIApplicationExitsOnSuspend key to your
application’s Info.plist file and setting its value to YES.
When an application opts out, it cycles between the not running,
inactive, and active states and never enters the background or
suspended states.
When the user taps the Home button to quit the application, the
applicationWillTerminate: method of the application delegate is called
and the application has approximately five seconds to clean up and
exit before it is terminated and moved back to the not running state."
See also: How to prevent my app from running in the background on the iPhone
The documentation is pretty explicit about this, "There is no API provided for gracefully terminating an iOS application." See Technical Q&A QA1561
How do I programmatically quit my iOS application?.
To be blunt, terminating an app to cleanup a socket is just like dealing with memory management by forcing an app to exit instead of calling release.
What about bringing up a modal view controller telling the user to quit the application? You could make this view controller without any dismiss button, so the user is obligated to kill the app.
How can I quit iPhone4 app? When I use exit(0) the app goes in the background. I want to quit the app instead of sending it to the background.
iPhone apps shouldn't have a quit button. The user quits by pressing the main button.
From Apple's docs: (http://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/MobileHIG.pdf)
People quit an iPhone application by opening a different application. In particular, note that people don’t tap an application close button or choose Quit from a menu. In iOS 4.0 and later, and on certain devices, the quitting application moves to a suspended state in the background. All iPhone applications should:
Be prepared to quit at any time. Therefore, save user data as soon as possible and as often as reasonable.
Save the current state when stopping, at the finest level of detail possible. For example, if your application
displays scrolling data, save the current scroll position.
iPhone applications should never quit programmatically because doing so looks like a crash to the user. There may be times, however, when external circumstances prevent your application from functioning as intended. The best way to handle this is to display an attractive screen that describes the problem and suggests how users can correct it. This helps users in two ways:
It provides feedback that reassures users that there’s nothing wrong with your application
It puts users in control, letting them decide whether they want to take corrective action and continue
using your application or press the Home button and open a different application
Set UIApplicationExitsOnSuspend in your application's plist. This will cause the app not to go into the background under iOS4 when the user switches to another app.
Then have your app send an openURL: message to Safari when your app wants to exit. When Safari launches, your app will be terminated (by honoring the UIApplicationExitsOnSuspend plist key).
If you point the Safari URL at a web page explaining why your app just stopped running, the user might be less likely to give it a 1-star rating.
Note that this procedure may or may not follow Apple's recommendations, but it does stay within legal public API use (e.g. even some of Apple's example apps launch Safari).
after that I put everything I had said I put this and it worked
- (Void) applicationDidEnterBackground: (UIApplication *) application
{
exit (0);
}
comes completely out of the application
in app delegate there is method call applicationDidEnterBackground
call the exit(0)
What is the proper way of ending an application on the iPhone when you are finished with it?
thanks,
anton
Jaanus is referring to this paragraph in the Apple iPhone Human Interface Guidelines
Stopping
People quit an iPhone application by opening a different application. In particular, note that people don’t tap an application close button or choose Quit from a menu. In iOS 4.0 and later, and on certain devices, the quitting application moves to a suspended state in the background. All iPhone applications should:
Be prepared to quit at any time. Therefore, save user data as soon as possible and as often as reasonable.
Save the current state when stopping, at the finest level of detail possible. For example, if your application displays scrolling data, save the current scroll position.
iPhone applications should never quit programmatically because doing so looks like a crash to the user. There may be times, however, when external circumstances prevent your application from functioning as intended. The best way to handle this is to display an attractive screen that describes the problem and suggests how users can correct it. This helps users in two ways:
It provides feedback that reassures users that there’s nothing wrong with your application
It puts users in control, letting them decide whether they want to take corrective action and continue using your application or press the Home button and open a different application
If certain circumstances prevent only some of your application's features from working, you can display either a screen or an alert when users activate the feature. Although an alert doesn't allow much flexibility in design, it can be a good choice if you can:
Describe the situation very succinctly
Supply a button that performs a corrective action
Display the alert only when users try to access the feature that isn’t functioning
As with all alerts, the less users see them, the more effective they are. For more information about creating alerts, see “Using Alerts.”
There is no way for an iPhone application to quit/terminate itself. Apple actively advises against it in their Human Interface and/or programming guides (can't remember which exactly) because it would look like a crash to the user.
An app should not terminate by itself.
Also, avoid showing an "exit screen" that prompts the user to quit the app manually as in iOS4, the app might stay open in the background and your user would be stuck in that exit state.