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.
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
When I restart the device my app is on it won't preserve the state it had once I open up the app again, it will be as if it's the first time I open, losing the session and having to re-login, how can I make my app preserve its state even through a device reboot? Like Twitter does, for example.
I'll try a bit more formal answer based on the comments you added above. I'll start by saying that the link Tim posted is something you should familiarize yourself with.
When your app is running, it's in the Foreground state. When you "exit" an app with the Home button, you're not really quitting it; you're just pushing it to the Background state. after a few seconds in background state, the OS automatically moves the app to the Suspended state. If you come back within a few minutes, your app is still in memory, so the OS just puts it back on the screen the way it was.
However, if you leave the app alone for a while and use other apps, the OS can--at any time and without warning--purge your app from memory. This is known as the "Not Running" state. Now, when the open the app again, it has to start from scratch. Obviously, the same thing happens when the device restarts--all apps are purged from memory.
The trick, then, is to save essential information about the app state whenever it enters the background state. You can use the app delegate's didEnterBackground method, or register for the UIApplicationDidEnterBackgroundNotification and invoke a method in your active view controller (or any other class, for that matter). Either way, you should save whatever state information you can.
How do you save this information? There are several strategies. For a simple app, perhaps you can register a few setting as NSUserDefaults. Or maybe you can write out a file containing whatever data the user was working on. It's really up to you.
Then, whenever the app launches, check for the presence of that saved data (however you chose to write it out), and set up the UI accordingly. To the user, it will appear as though the app never quit, which is exactly what Apple wants them to think.
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.