I am working on an iphone game app. I dont want to use core data or nsuserdefaults to store user data. instead i want to keep all activities in memory and then send it to server when user goes back to previous screen, ends game or presses the home button of iphone. Now everything works fine but i am not able to sync user data when user presses home button. I have implemented the appilcationWillTerminate method in my delegate class but its not working out for me as the method is not get called when I press home button of iphone. Can anyone please tell me how to achieve this task?
best regards
What about this method:
Tells the delegate that the application is now in the background.
- (void)applicationDidEnterBackground:(UIApplication *)application
From Apple Docs:
In iOS 4.0 and later, this method is called instead of the applicationWillTerminate: method when the user quits an application that supports background execution. You should use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. You should also disable updates to your application’s user interface and avoid using some types of shared system resources (such as the user’s contacts database). It is also imperative that you avoid using OpenGL ES in the background.
Your implementation of this method has approximately five seconds to perform any tasks and return. If you need additional time to perform any final tasks, you can request additional execution time from the system by calling beginBackgroundTaskWithExpirationHandler:. In practice, you should return from applicationDidEnterBackground: as quickly as possible. If the method does not return before time runs out your application is terminated and purged from memory.
You should use NSUserDefaults to store data about the application state. Then, when the application re-starts, you can load the data from NSUserDefaults to recreate the previous state. However with the new multitasking this is not as necessary as it used to be a couple of years ago.
Related
As in my application if some action regarding "httpcall" are posted in the mainthread and my app is waiting for a response from server and same time home button is pressed than although app is entering background but IOS delegates (such as "didEnterBackground") are not getting called till the response are received.
Also sometime even if I'm relaunching the app its not responding till it gets crashed by itself.
Note:I'm using CyberLink code for my HTTP posts.
As Apple says :
You should use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. You should also disable updates to your application’s user interface and avoid using some types of shared system resources (such as the user’s contacts database)
I think you try to do something in background, for which didEnterBackground is not enough. Use Grand Central Dispach istead.
Since your Http method are of synchronous type ..Your UI will froze till response.
What you have done is in simple words tell the OS to perform these http requests before doing anything else.
On pressing home the system will wait..for a few seconds to receive a response..otherwise it will quit thee app. since it violates app guidelines..(you are blocking OS indefinitely)
The didEnterBackground will be called only if these requests will be finished or will not be called in the case when OS decides to terminate your app.
I've just been reading this post on notifications being sent to apps running in the background :
Not getting didReceiveMemoryWarning when app is in the background
My question is that since an app in the background will not act on a didRecieveMemoryWarning until it enters the foreground again, what is the recommended way to free up memory in your app if it is running in the background when the memory notification is sent - or is this not possible ?
In iOS 4.0 and later, - (void)applicationDidEnterBackground:(UIApplication *)application method is called instead of the applicationWillTerminate: method when the user quits an application that supports background execution.
You should use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
You should also disable updates to your application’s user interface and avoid using some types of shared system resources (such as the user’s contacts database). It is also imperative that you avoid using OpenGL ES in the background.
Your implementation of this method has approximately five seconds to perform any tasks and return. If you need additional time to perform any final tasks, you can request additional execution time from the system by calling beginBackgroundTaskWithExpirationHandler:. In practice, you should return from applicationDidEnterBackground: as quickly as possible. If the method does not return before time runs out your application is terminated and purged from memory.
If your app is running in the background (because it is, for example, a Voice over IP app that is allowed to run in the background), it will receive memory warning notifications in the same way as if it were running in the foreground, and you should deal with them accordingly.
However, if your app is suspended in the background, it won't receive memory warnings or other notifications. Your job is to free as much memory as possible before your app enters the background. Once you're in the background, you have no way to do anything anymore. The OS will decide whether to kill your app or not (without notifying you again) at its discretion.
What do you all recommend as the best location in an iphone project to dump data collected from the user to a local file? Would you say that applicationWillTerminate is a good option?
Thanks!
A better option on iOS 4.x is applicationDidEnterBackground:
Indeed, according to Apple docs, an application in the background can be terminated at any time due to low memory conditions. Therefore, the suggestion is making persistent any state information at the moment the app enters background.
An excerpt from the UIApplicationDelegate protocol:
You should use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. You should also disable updates to your application’s user interface and avoid using some types of shared system resources (such as the user’s contacts database). It is also imperative that you avoid using OpenGL ES in the background.
Your implementation of this method has approximately five seconds to perform any tasks and return. If you need additional time...
Also from Apple Docs for applicationWillTerminate:
For applications that do not support background execution or are linked against iOS 3.x or earlier, this method is always called when the user quits the application. For applications that support background execution, this method is generally not called when the user quits the application because the application simply moves to the background in that case. However, this method may be called in situations where the application is running in the background (not suspended) and the system needs to terminate it for some reason.
Therefore if you specifically request to not support backgrounding for your app or you link against iOS 3.x you should consider persisting in both places (applicationWillTerminate and applicationWillEnterBackground) to catch situations as well.
My application uses NSUserDefaults to store some values so that it can restore them on application update or if backgrounding is quit. Backgrounding automatically saves my integer values, but if the user quits the application from the launcher, the numbers are lost too, and the ViewDidUnload method I guess doesn't evoke when entering backgrounding. Is there a way that I can save the NSUserDefaults any time the application unloads. Also, the ViewDidLoad method had the same problem, it doesn't evoke from backgrounding. What's a way around this?
P.S. So far the only data my application needs to save is an int for an on-screen count.
UPDATE: UIApplicationDidEnterBackgroundingNotification works great with your suggestions!
You can't save data right before it eventually gets killed, but you can save state 'just in case' in your applicationDidEnterBackground: app delegate.
There's also applicationDidBecomeActive:, but there's no reason to load your save data from there, since when it's invoked from an app that was in the background, the data will have been preserved any way.
You can't tell if your app was launched from the background or not, at least how it's currently set up, since your app delegate will get the same sequence of events if it's launched from springboard.
As Joost says, you should save anything you need to restore state inside the applicationDidEnterBackground callback; essentially, you should assume this is the last message your app will get before it gets killed mercilessly by an evil process reaper.
You should check out the WWDC 2010 Session Videos, specifically, Session 105 - Adopting Multitasking on iPhone OS, Part 1 for a thorough explanation.
I am developing one game application for iphone.Here whenever user get the call or SMS or he quit the appication ,my application should be in pause state .so,whenever he loads the application again,it should go to previous state where it stopped. Are there any built-in methods for doing this
Thanks all
Implement notification for UIApplicationWillTerminateNotification (and probably UIApplicationWillResignActiveNotification as well). That way your objects can save their state, and restore it when the application is relaunched. There are notifications for that, too, but you are more likely to want to read in the old state data when the objects receive their init calls.
You should consider all the usual storage mechanisms for state - NSUserDefaults, plists, and CoreData. The choice is up to you.
It is you who have to handle all this stuff. You have to save your object state into some file and reload the file when the app re-launches. The system provides you an opportunity to save the state by throwing notifications where in you have little time to archive your objects. Try to design your app such that the objects are not heavy weight and prioritize the object archiving tasks.