I'm developing an iOS app that uses CoreLocation in order to manage iBeacons. I have Beacon detection in both the AppDelegate and ViewController, but I want the AppDelegate detection to only work when the app is in background state. I send analytics to a server when the user enters or leaves a region, so if both (AppDelegate and ViewController) detections work when the app is in Foreground, the app will send doubled analytics.
Any solutions to make a code (the server call to send analytics) not to run when the app is in Foreground?
In AppDelegate start your beacon detection in the applicationDidEnterBackground: method and stop beacon detection in the applicationWillEnterForeground: method.
Simply implement methods in your AppDelegate to track if you are in the foreground, and stop sending analytics from your AppDelegate if so. See below:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
_sendAnalytics = YES;
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
_sendAnalytics = NO;
}
Then add an if statement before sending analytics from the AppDelegate to check the value of _sendAnalytics.
Centralizing this logic as #paulw11 suggests in his comment would probably make the code cleaner, but if you do need to send analytics in two places, the above will solve your problem.
Related
I am writing an iOS VoIP app that has background mode permission. In background, it will be listening for incoming connection, and once I have an incoming connection, it should start a UIViewController for the user to accept the call. How and where to call and present a UIViewController from background?
I know how to do this in Android, a Service would call an Activity via an Intent.
But in iOS , I am not sure how would the flow go. Also, how do I go into background mode in iOS? I know it has to do with the appDelegate method applicationDidEnterBackground: , But not sure what to do next.
Thanks in advance.
there are two methods in appDelegate that will be called when the app returns to active state. First one is - (void)applicationWillEnterForeground:(UIApplication *)application and the second one is - (void)applicationDidBecomeActive:(UIApplication *)application
In the 2nd you have to restore your user interface.
It is a very simple example. I cannot explain why these lines of code cause a crash. I only want to create multiple threads in a for loop.
In the AppDelegate:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
for (int i = 0; i < 5; i++) {
[self performSelectorInBackground:#selector(workInBackground)
withObject:nil];
}
return YES;
}
-(void)workInBackground{
}
The app crashes only sometimes (lldb crash, iPhone Simulator 5.0 - 6.1, Xcode Version 4.6.2). I use ARC.
Can anyone explain this behavior?
Update
I "solved" the problem. When I perform a cleanup before each test, the crash no longer occurs.
I don't know what the problem is, but you should check this out:
What are the differences between didFinishLaunchingWithOption and viewDidLoad
Also you could use NSOperationQueue if you have multiple task that you want to run in background.
Ok, so if you read the apple documetation they say: "This method is called after state restoration has occurred but before your app’s window and other UI have been presented. At some point after this method returns, the system calls another of your app delegate’s methods to move the app to the active (foreground) state or the background state." this mean that actually the app in this point in not yet in the foreground state, here you should store somewhere the intention to start your threads, and after that the sistem call the method - (void)applicationDidBecomeActive:(UIApplication *)application, at this point you are absolutelly sure that your app is in a foreground state and active, now if you have recorded the intention to start your threads you can do it, and don't forget to reset the intention variable status
I am making an iPhone application that is fairly simple. All I need to do is set the bool "paused" to true to pause the game. How can I make my application do that when the home button is hit?
Thanks guys, that was exactly what I wanted. Since it is in the appDelegate, though, I can't access the boolean "paused" to change it. How can I make it global so that I can access it from the appDelegate?
The Appdelegate.m of your app provides functions you can use to track if the Application will be entering the background;
User pressed the button;
- (void)applicationWillResignActive:(UIApplication *)application
Application is in the background;
- (void)applicationDidEnterBackground:(UIApplication *)application
Within any of these functions you could set the BOOL to True/YES. -> See the comments provided by Apple within the functions for their exact usage.
When the application becomes active again, the appdelegate will (again) fire a function;
- (void)applicationDidBecomeActive:(UIApplication *)application
In your AppDelegate there are two method which is called when the button is called
You can pause the game here:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
//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.
}
or here:
- (void)applicationWillResignActive:(UIApplication *)application{
//Sent when the application is about to move from active to inactive state.
}
In your app delegate, implement applicationWillResignActive:. Set paused = YES; there.
Reset it in applicationDidBecomeActive:.
- (void)applicationWillResignActive:(UIApplication *)application
implement your pause method and it will be called when your app is going to become inactive.
Is there an API that allows me to know when NotificationCenter will pop a notification on the top of the screen while my app is running (for example for an incoming Message or email)?
It causes a big performance glitch to my game so I'd like to pause it and unpause once the notification has disappeared. If there is no event to listen to I can only think of monitoring FPS and pausing for a few seconds if it drops below a threshold. Any other suggestions?
EDIT: My answer is only for popup notifications, not for the ones that scroll on to the top of the screen. Sorry :(
In your app delegate, the method
- (void)applicationWillResignActive:(UIApplication *)application
will be called.
And then
- (void)applicationDidBecomeActive:(UIApplication *)application
when it's time to start up again.
Which is the proper delegate to implement when an application is waking up from being in the background and you want it to prep it to be active?
applicationWillEnterForeground vs applicationDidBecomeActive -- What's the difference?
Which is the proper delegate to implement for when an application is going to sleep and you want to prep it to cleanup and save data?
applicationWillResignActive vs. applicationDidEnterBackground -- What's the difference?
Also, I've noticed that applicationWillResignActive gets called when an incoming SMS or call comes in but the user chooses to click Ok and continue. I don't want my app to take any action in these cases. I just want it to keep running without any intermediate cleanup since the user didn't exit the app. So, I would think it makes more sense to do cleanup work just in applicationDidEnterBackground.
I would appreciate your input on best practices to follow on choosing which delegates to implement for waking up and going to sleep as well as considering events like being interrupted by SMS/calls.
Thanks
When waking up i.e. relaunching an app (either through springboard, app switching or URL) applicationWillEnterForeground: is called. It is only executed once when the app becomes ready for use, after being put into the background, while applicationDidBecomeActive: may be called multiple times after launch. This makes applicationWillEnterForeground: ideal for setup that needs to occur just once after relaunch.
applicationWillEnterForeground: is called:
when app is relaunched
before applicationDidBecomeActive:
applicationDidBecomeActive: is called:
when app is first launched after application:didFinishLaunchingWithOptions:
after applicationWillEnterForeground: if there's no URL to handle.
after application:handleOpenURL: is called.
after applicationWillResignActive: if user ignores interruption like a phone call or SMS.
applicationWillResignActive: is called:
when there is an interruption like a phone call.
if user takes call applicationDidEnterBackground: is called.
if user ignores call applicationDidBecomeActive: is called.
when the home button is pressed or user switches apps.
docs say you should
pause ongoing tasks
disable timers
pause a game
reduce OpenGL frame rates
applicationDidEnterBackground: is called:
after applicationWillResignActive:
docs say you should:
release shared resources
save user data
invalidate timers
save app state so you can restore it if app is terminated.
disable UI updates
you have 5 seconds to do what you need to and return the method
if you don't return within ~5 seconds the app is terminated.
you can ask for more time with beginBackgroundTaskWithExpirationHandler:
The official documentation.
Managing Your App's Life Cycle is helpful to your questions. For quick concept, you can see Figures in that document.
You can also read the comment from the code generated by the XCode Wizard. Listed as follows:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
return YES;
}
- (void)applicationWillResignActive:(UIApplication *)application
{
/*
Sent when the application is about to move from active to inactive state.
This can occur for certain types of temporary interruptions (such as an
incoming phone call or SMS message) or when the user quits the application
and it begins the transition to the background state.
Use this method to pause ongoing tasks, disable timers, and throttle down
OpenGL ES frame rates. Games should use this method to pause the game.
*/
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
/*
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.
If your application supports background execution, this method is called
instead of applicationWillTerminate: when the user quits.
*/
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
/*
Called as part of the transition from the background to the active state;
here you can undo many of the changes made on entering the background.
*/
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
/*
Restart any tasks that were paused (or not yet started) while the
application was inactive. If the application was previously in the
background, optionally refresh the user interface.
*/
}
- (void)applicationWillTerminate:(UIApplication *)application
{
/*
Called when the application is about to terminate.
Save data if appropriate.
See also applicationDidEnterBackground:.
*/
}
For more detailed explanations, please refer to official document for UIApplicationDelegate
I was still a bit confused with Dano's answer so I did a little test to get the flow of events in certain scenarios for my reference, but it might be useful to you too. This is for apps that DO NOT use UIApplicationExitsOnSuspend in their info.plist. This was conducted on an iOS 8 simulator + confirmed with iOS 7 device. Please excuse Xamarin's event handler names. They are very similar.
Initial and all subsequent launches from a not-running state:
FinishedLaunching
OnActivated
Interruption (phone call, top slide-down, bottom slide-up):
Home button double-press listing inactive apps, then reselecting our app:
OnResignActivation
OnActivated
Home button double-press listing inactive apps, selecting another app, then relaunching our app:
Home button single press, then relaunch:
Lock (on/off button), then unlock:
OnResignActivation
DidEnterBackground
WillEnterForeground
OnActivated
Home button double-press, and terminate our app: (subsequent relaunch is first case)
OnResignActivation
DidEnterBackground
DidEnterBackground (iOS 7 only?)
Yes, DidEnterBackground is called twice on iOS7 device. Both times UIApplication state is Background. However, iOS 8 simulator does not. This needs testing on iOS 8 device. I will update my answer when I get my hand on it, or someone else could confirm.
applicationWillEnterForeground is called:
when app is relaunched(comes from background to foreground)
This method is not invoked when app starts for the first time i.e when applicationDidFinishLaunch is called but only when comes from background
applicationDidBecomeActive
applicationDidBecomeActive is called
when app is first launched after didFinishLaunching
after applicationWillEnterForeground if there’s no URL to handle.
after application:handleOpenURL: is called.
after applicationWillResignActive if user ignores interruption like a phone call or SMS.
after disappearing of alertView anywhere from the application
applicationWillResignActive is called when system is asking for permissions. (in iOS 10). Just in case someone hit into the same trouble as me...
In iOS 8+ there is a subtle but important difference for taking phone call.
In iOS 7 if user takes phone call both applicationWillResignActive: and applicationDidEnterBackground: are called. But in iOS 8+ only applicationWillResignActive: is called.
For iOS 13+ the following methods will be executed:
- (void)sceneWillEnterForeground:(UIScene *)scene
- (void)sceneDidBecomeActive:(UIScene *)scene