Push notification not received when App is in Background in iOS 10

Question

I'm using FCM(Firebase Cloud Messaging) for sending push notifications in iOS.

I'm able to receive the notification when App is in foreground state. But when the App is in background state, the notification is not received. Whenever the application will come to foreground state, only then will the notification be received.

My code is:

- (void)userNotificationCenter:(UNUserNotificationCenter *)center
   willPresentNotification:(UNNotification *)notification
     withCompletionHandler:(void (^)(UNNotificationPresentationOptions))completionHandler {
// Print message ID.
NSDictionary *userInfo = notification.request.content.userInfo;
NSLog(@"Message ID: %@", userInfo[@"gcm.message_id"]);

// Pring full message.
NSLog(@"%@", userInfo);

if( [UIApplication sharedApplication].applicationState == UIApplicationStateInactive )
{
    NSLog( @"INACTIVE" );
    completionHandler(UNNotificationPresentationOptionAlert);
}
else if( [UIApplication sharedApplication].applicationState == UIApplicationStateBackground )
{
    NSLog( @"BACKGROUND" );
    completionHandler( UNNotificationPresentationOptionAlert );
}
else
{
    NSLog( @"FOREGROUND" );
    completionHandler( UNNotificationPresentationOptionAlert );
}}



- (void)applicationDidEnterBackground:(UIApplication *)application {


}

When App is in background state:

- (void)userNotificationCenter:(UNUserNotificationCenter *)center
   willPresentNotification:(UNNotification *)notification
     withCompletionHandler:(void (^)(UNNotificationPresentationOptions))completionHandler

-- is not called at all.

I enabled push notifications and also remote notifications in background modes in App Capabilities. But App is still not receiving the notification.

I referred to some StackOverflow questions but wasn't able to solve the issue. Is there anything to add in iOS version 10 or any mistake in my code?

Solution

For iOS 10, we need to call the 2 methods below.

For FOREGROUND state

- (void)userNotificationCenter:(UNUserNotificationCenter *)center  willPresentNotification:(UNNotification *)notification withCompletionHandler:(void (^)(UNNotificationPresentationOptions options))completionHandler  
{  
    NSLog( @"Handle push from foreground" );  
    // custom code to handle push while app is in the foreground  
    NSLog(@"%@", notification.request.content.userInfo);
    completionHandler(UNNotificationPresentationOptionAlert);
} 

For BACKGROUND state

- (void)userNotificationCenter:(UNUserNotificationCenter *)center didReceiveNotificationResponse:(UNNotificationResponse *)response withCompletionHandler:(void (^)())completionHandler  
{  
    NSLog( @"Handle push from background or closed" );  
    // if you set a member variable in didReceiveRemoteNotification, you  will know if this is from closed or background  
    NSLog(@"%@", response.notification.request.content.userInfo);
    completionHandler();
}  

Before that, we must add the UserNotifications framework and import in the AppDelegate.h file

#import <UserNotifications/UserNotifications.h>  
@interface AppDelegate : UIResponder <UIApplicationDelegate,UNUserNotificationCenterDelegate>