My app has to run for a long time (also) in the background, due to Location Services.
When a certain condition is met the app has to move to the foreground.
I was able to run my app in the background and bring it to the front manually.
Reading up on this issue I got confused on how to move my app to the foreground by code.
It has to be in an if statement but what to do from here?
No do not think this is possible. You will be able to spawn a UILocalNotification to show application state to the user, but it is my understanding that iOS prevents you from making your app take focus.
you can't do that without user interaction. You can present a UILocalNotification
-- you can't even be sure iOS leaves it running though!
on a jailbroken phone I guess it is possible
This is clearly not possible, as it would be a mess if any app could just take over control at any point in time. As mentioned, you have to post a notification, and then it is up to the user if he or she wants to launch the app. If you notification states a good reason why they should launch your app, they might very well do it :-) And remember, don't mix up the user's needs with your/your app's needs.
Related
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 You're supposed to notify the user via an UIAlertView about the outdated app and disable interaction with the app.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
I wrote my first iPhone App, and managed to get it into the App store. I later discovered a bug that happens on a real device but not on my emulator. I have committed a fix (changed plist to prevent app running in background), but I don't really understand why it happened.
My App allows users to record a sound-byte, however while they are recording they can use the iPhone home button to move the app to the background, and then it can keep recording forever if they don't restart the phone or the app does not crash.
My impression from everything I have read, is that this should not happen as you have to ask for background audio specifically if you want to do this, but now it appears to me that you have to ask specifically to disable it.
Could anyone explain this to me?
The iOS App lifecycle is described in Apple's iOS App Programming Guide.
The App is given the opportunity to save data and otherwise stop things that don't need to be running, before being suspended. You can request extra time doing this by using beginBackgroundTaskWithExpirationHandler:.
If you want your app to stop doing its "normal thing" when it is put into the background then you need to detect the App state transition and stop it yourself.
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.
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.
I am fairly new to iphone app development. I am creating an app that has multiple views. Initially it starts with a view for authentication and then load views according to user interaction. When I build and run the app - the first time it shows the "Default.png" screen and then shows the first view where I do my authentication process (typing in userid,password and do a web service) and then after the credentials are verified it takes me to the next view. When I close the app at this state in the simulator and reopen it again, I am seeing the same state in which I closed my app. But here is what I want. When I relaunch the app I should be able to show the "DEfault.png" and screen and then show my initial authentication view. Can you please help me out on this ? Thanks
It sounds like the problem you are trying to solve is that your authenticated session may time out while the app is suspended and you need to log in again.
Although the proposed solution (setting UIApplicationExistsOnSuspend to true) would work I think you should consider a different approach.
Apple recommends that you do everything you can to make it look like the phone supports multitasking. That is why, by default, your app will suspend and resume instead of exit and relaunch. In your case, though, you may need to re-login to resume the session. I offer you a couple of alternate solutions:
Cache the credentials (ie username and password) and silently use them to resume the session when needed. If the back-end supports this.
Detect when the session has become stale and bring in a view to inform the user that the session has expired and ask them to log in again. This would also address the issue if the user keeps the app active past the timeout of the session.
Both of these approaches should improve perceived app performance and integrate better into the Apple usability guidelines.
That's because iOS 4 apps are supposed to support multitasking. You can change the app so it doesn't: In Info.plist, set UIApplicationExitsOnSuspend to true (i.e. <key> UIApplicationExitsOnSuspend</key><true/>) — make sure it's a boolean and not a string. Note that this will probably make startup slower, since the app has to be launched again.
The other way is to handle applicationDidEnterBackground: in your app delegate and do two things:
Reset your view hierarchy (you can do this on next launch, but doing it earlier might help to free more memory)
Show "Default.png" in a full-screen view — iOS takes a screenshot of your app after it's hidden which it uses to animate the app back in.