applicationDidEnterBackground only works in appdelegate class

[Error404]

Hi,

When the program goes into background mode, I want to do do a little something inside some of my classes... However, when i put the:

- (void) applicationDidEnterBackgroundUIApplication *)application { }

inside my class, It doesn't get called... Only when its inside the main appdelegate class..

How do you make it work inside any class?

Thanks

[Duncan C]

Originally Posted by Error404

Hi,

When the program goes into background mode, I want to do do a little something inside some of my classes... However, when i put the:

- (void) applicationDidEnterBackgroundUIApplication *)application { }

inside my class, It doesn't get called... Only when its inside the main appdelegate class..

How do you make it work inside any class?

Thanks

You don't. applicationDidEnterBackground is an app delegate method. The UIApplication object sends this message to the app delegate, and ONLY to the app delegate.

You could have your app delegate broadcast an NSNotification, and then any of your objects could listen for that notification. Something like this:

- (void) applicationDidEnterBackground:(UIApplication *)application 
{   
  [[NSNotificationCenter defaultCenter] postNotificationName: @"didEnterBackground" 
    object: nil 
    userInfo: nil];
}

And in any object that you want to get, in it's init method:

  [[NSNotificationCenter defaultCenter] addObserver: self 
    selector: @selector(enteredBackground:) 
    name: @"didEnterBackground" 
    object: nil];

That will cause the object's enteredBackground: method to be called when the app enters the background. (It will crash if the object doesn't have a enteredBackground: method)

[Error404]

Originally Posted by Duncan C

You don't. applicationDidEnterBackground is an app delegate method. The UIApplication object sends this message to the app delegate, and ONLY to the app delegate.

You could have your app delegate broadcast an NSNotification, and then any of your objects could listen for that notification. Something like this:

- (void) applicationDidEnterBackground:(UIApplication *)application 
{   
  [[NSNotificationCenter defaultCenter] postNotificationName: @"didEnterBackground" 
    object: nil 
    userInfo: nil];
}

And in any object that you want to get, in it's init method:

  [[NSNotificationCenter defaultCenter] addObserver: self 
    selector: @selector(enteredBackground:) 
    name: @"didEnterBackground" 
    object: nil];

That will cause the object's enteredBackground: method to be called when the app enters the background. (It will crash if the object doesn't have a enteredBackground: method)

Amazing! I dont know why, but I never used notifications before.. it will, beside fixing this challenge, help me a lot in the future.

Thanks a lot

Cheers

[Mixsiah]

[quote=Duncan C;239328]You don't. applicationDidEnterBackground is an app delegate method. The UIApplication object sends this message to the app delegate, and ONLY to the app delegate.

You could have your app delegate broadcast an NSNotification, and then any of your objects could listen for that notification. Something like this:

- (void) applicationDidEnterBackground:(UIApplication *)application 
{   
  [[NSNotificationCenter defaultCenter] postNotificationName: @"didEnterBackground" 
    object: nil 
    userInfo: nil];
}

And in any object that you want to get, in it's init method:

  [[NSNotificationCenter defaultCenter] addObserver: self 
    selector: @selector(enteredBackground:) 
    name: @"didEnterBackground" 
    object: nil];

------
Where do you place this code? in a method that I want to call?

Example I want the reloadData method to be called via the NSTimer, where would I place this NSNotification code?

[Duncan C]

[quote=Mixsiah;245128]

Originally Posted by Duncan C

You don't. applicationDidEnterBackground is an app delegate method. The UIApplication object sends this message to the app delegate, and ONLY to the app delegate.

You could have your app delegate broadcast an NSNotification, and then any of your objects could listen for that notification. Something like this:

- (void) applicationDidEnterBackground:(UIApplication *)application 
{   
  [[NSNotificationCenter defaultCenter] postNotificationName: @"didEnterBackground" 
    object: nil 
    userInfo: nil];
}

And in any object that you want to get, in it's init method:

  [[NSNotificationCenter defaultCenter] addObserver: self 
    selector: @selector(enteredBackground:) 
    name: @"didEnterBackground" 
    object: nil];

------
Where do you place this code? in a method that I want to call?

Example I want the reloadData method to be called via the NSTimer, where would I place this NSNotification code?

Notifications and timers are two different things. The original poster was asking for a way for objects other than the app delegate to be notified when the app enters the background.

If you have questions about using timers you should start a new thread.

If you want other objects to be notified about applicationDidEnterBackground messages, the description above tells you exactly where to put it. The applicationDidEnterBackground method goes in the app delegate.

If you have another object, like a view controller, that you want to get a notice when the app gets a did enter background, you add 2 things to the object that you want to be notified:

1. Put the addObserver call (above) in that object's init method.

2. You then need to write an enteredBackground: method method with the following signature:

- (void) enteredBackground: (NSNotification*) notification;


That's it.

[Mixsiah]

[quote=Duncan C;245133]

Originally Posted by Mixsiah

Notifications and timers are two different things. The original poster was asking for a way for objects other than the app delegate to be notified when the app enters the background.

If you have questions about using timers you should start a new thread.

If you want other objects to be notified about applicationDidEnterBackground messages, the description above tells you exactly where to put it. The applicationDidEnterBackground method goes in the app delegate.

If you have another object, like a view controller, that you want to get a notice when the app gets a did enter background, you add 2 things to the object that you want to be notified:

1. Put the addObserver call (above) in that object's init method.

2. You then need to write an enteredBackground: method method with the following signature:

- (void) enteredBackground: (NSNotification*) notification;


That's it.

Hi Duncan

I am a newbie so please bare with me...


Yes the timer works perfectly, I now just need to keep the app running in the background.

I dont know where the init method is? Can you please tell me how to do this? and where to put it?


Yes I have a viewcontroller which is where all the methods execute like NSTimer, refresh data etc...

[Mixsiah]

[quote=Duncan C;245133]

Originally Posted by Mixsiah

Notifications and timers are two different things. The original poster was asking for a way for objects other than the app delegate to be notified when the app enters the background.

If you have questions about using timers you should start a new thread.

If you want other objects to be notified about applicationDidEnterBackground messages, the description above tells you exactly where to put it. The applicationDidEnterBackground method goes in the app delegate.

If you have another object, like a view controller, that you want to get a notice when the app gets a did enter background, you add 2 things to the object that you want to be notified:

1. Put the addObserver call (above) in that object's init method.

2. You then need to write an enteredBackground: method method with the following signature:

- (void) enteredBackground: (NSNotification*) notification;


That's it.

Does that code go into the main.m ?

int main(int argc, char *argv[]) {

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
int retVal = UIApplicationMain(argc, argv, nil, nil);
[pool release];
return retVal;

//Here is the inserted code?

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(enteredBackground) name: @"didEnterBackground" object: nil];

}

[smasher]

There's a set of notifications that automatically gets sent by the system, so you don't have to send your own.

UIApplication Class Reference

Just sign up for UIApplicationDidEnterBackgroundNotification from [UIApplication sharedApplication]. I didn't compile, but this should work:

  [[NSNotificationCenter defaultCenter] addObserver: whatever
    selector: @selector(enteredBackground:) 
    name: UIApplicationDidEnterBackgroundNotification
    object: nil];