Codename One iOS Remote Notifications

[ASDApp]

We have been trying for the last two weeks to get a reliable solution to try and sync our app data with a server in the background. We have tried the Background fetch mechanism but due to the iOS restrictions on when it runs it is not a viable solution.

iOS does provide Remote Notifications (https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app?language=objc) that we would like to use as we can use the same mechanism on Android.

The issues is that when sending a type 2 notification CN1 only delivers the notification when the app is brought to the foreground by the user.

On Android I see there is a Build Hint for android.background_push_handling that allows the notifications to be sent to the app even if it is in the background.

Is there a similar build hint that we can use for iOS?

If not, is there a way then to override the application:didReceiveRemoteNotification:fetchCompletionHandler: method that fires when the Notification arrives so that we can forward it to our app?

---

Turns out we already support the content-available: 1 mode in the push server and use it by default when sending a #2 type push message. We're still missing a callback in our delegate so it would work but that should be a relatively easy fix. Please file an issue and we'll try to address it within the next couple of weeks: github.com/codenameone/CodenameOne/issues – Shai Almog Oct 8 at 2:01

[shannah]

Notes:

Played with this a little bit today but was unable to receive Type 2 push in my test app on iOS at all. Testing on iPhone X 13.3.1.

I'm not certain yet, but it is possible that background notifications now require the HTTP API (we are using the binary API).

From Creating Background Notification:

Additionally, the notification’s POST request should contain the apns-push-type header field with a value of background, and the apns-priority field with a value of 5. The APNs server requires the apns-push-type field when sending push notifications to Apple Watch, and recommends it for all platforms. For more information, see Create and Send a POST Request to APNs.

Since the binary API doesn't have an equivalent to HTTP headers (that I can find) we can't set the "apns-push-type" or "apns-priority" fields as described here.

I could be doing something else fundamentally wrong here, but if we do need to upgrade to the HTTP API for this feature, that would move it out of the category of "trivial" and likely wouldn't make it into 7.0.

[shannah]

This Article includes relevant details:

APNS Priority must be set to 5 for background notifications
Many notification delivery systems set the apns-priority header value to 10 (immediate delivery). Or, if this header is omitted, a value of 10 is the default assumed by Apple.

The other possible value of the apns-priority header is 5. This lower value reduces battery usage, but may result in the notification being delayed.

In a 2019 WWDC session, Apple said that a value of 5 is now required for all “content-available” notifications. These are notifications that may not contain user-visible data, but are used to invoke the app in the background to download updated content, such as recently received messages. Omitting this may cause the app to not launch.

[javieranton-zz]

Here is a way to achieve this. beware that doing this will disable CN1's default iOS interface notification methods in your main class (also need to disable push build hint), so you'll need to call your own exposed static ones directly from native. There is no way to do pre-fetch or do real background (while inactive/full bg) processing with CN1 in my experience, app needs to go to fg (unless you use this code). Note this is an example, your meta payload will vary. You can safely persist things via NSUserDefaults as seen below so that you can recover values later when app is in fg at some point
This is very time-consuming, apologies if sharing this actually distracts. I cannot offer more support, but thought of sharing
1- Remove (via xCode from sources) below code in Ports/iOSPort/nativeSources/CodenameOne_GLAppDelegate.m between lines 159 and 169:

#ifdef CN1_INCLUDE_NOTIFICATIONS
    if (@available(iOS 10, *)) {
        if (isIOS10()) {
            UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
            center.delegate = self;
            [center requestAuthorizationWithOptions:(UNAuthorizationOptionSound | UNAuthorizationOptionAlert | UNAuthorizationOptionBadge) completionHandler:^(BOOL granted, NSError * _Nullable error){
                if( !error ) {}
            }];
        } 
    }
#endif

2- ios.afterFinishLaunching. Define the below in your native obj c interface and call it from ios.afterFinishLaunching with something like this (registerPushFromAfterFinishedLaunching is a static method exposed in your java code that calls your native registerPush)
ios.afterFinishLaunching
your_native_namespace_registerPushFromAfterFinishedLaunching__(CN1_THREAD_GET_STATE_PASS_SINGLE_ARG);

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

- (void)userNotificationCenter:(UNUserNotificationCenter *)center didReceiveNotificationResponse:(UNNotificationResponse *)response withCompletionHandler:(void (^)())completionHandler {
}

-(void)registerPush{
    if (@available(iOS 10, *)) {
        UNUserNotificationCenter* center = [UNUserNotificationCenter currentNotificationCenter];
        //surprisingly, not necessary
        //center.delegate = self;
        [center requestAuthorizationWithOptions:(UNAuthorizationOptionAlert + UNAuthorizationOptionSound + UNAuthorizationOptionBadge)
                completionHandler:^(BOOL granted, NSError * _Nullable error) {
                if (granted) {
                    [[UIApplication sharedApplication] registerForRemoteNotifications];
                }
            }];
    }else
    {
        UIUserNotificationType userNotificationTypes = (UIUserNotificationTypeAlert | UIUserNotificationTypeBadge | UIUserNotificationTypeSound);
        UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:userNotificationTypes categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    }
}

Your native .h file should extend NSObject<UNUserNotificationCenterDelegate> and import #import <Foundation/Foundation.h> #import <UserNotifications/UserNotifications.h>
3-//ios.glAppDelegateBody (example)

    - (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData*)deviceToken {
const unsigned *tokenBytes = [deviceToken bytes];
NSString *tokenAsString = [NSString stringWithFormat:@"%08x%08x%08x%08x%08x%08x%08x%08x",
ntohl(tokenBytes[0]), ntohl(tokenBytes[1]), ntohl(tokenBytes[2]),
ntohl(tokenBytes[3]), ntohl(tokenBytes[4]), ntohl(tokenBytes[5]),
ntohl(tokenBytes[6]), ntohl(tokenBytes[7])];
JAVA_OBJECT str = fromNSString(CN1_THREAD_GET_STATE_PASS_ARG tokenAsString);
your_namespace_iosPushRegistered___java_lang_String(CN1_THREAD_GET_STATE_PASS_ARG str); 
}
- (void)application:(UIApplication *)application didFailToRegisterForRemoteNotificationsWithError:(NSError *)error {  
  JAVA_OBJECT str = fromNSString(CN1_THREAD_GET_STATE_PASS_ARG error.localizedDescription); 
  your_namespace_iosPushError___java_lang_String(CN1_THREAD_GET_STATE_PASS_ARG str); 
    } 

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
NSString *metaInfo = [userInfo valueForKey:@"meta"];
NSData *data = [metaInfo dataUsingEncoding:NSUTF8StringEncoding];
id metaJson = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSString *notifId = [metaJson valueForKey:@"notifId"];
NSString *senderId = [metaJson valueForKey:@"senderId"];
UIApplicationState state = [[UIApplication sharedApplication] applicationState];
if(state == UIApplicationStateActive)
{
    JAVA_OBJECT strNotifId = fromNSString(CN1_THREAD_GET_STATE_PASS_ARG notifId);
    JAVA_OBJECT strSenderId = fromNSString(CN1_THREAD_GET_STATE_PASS_ARG senderId);
    your_namespace_iosActivePushReceived___java_lang_String_java_lang_String(CN1_THREAD_GET_STATE_PASS_ARG strNotifId, strSenderId);
    completionHandler(UIBackgroundFetchResultNoData);
}
else
{
    NSUserDefaults *shared = [[NSUserDefaults alloc] initWithSuiteName:@"some.unique.id"];
    [shared setBool:YES forKey:@"bgPushReceived"];
    __block UIBackgroundTaskIdentifier bgTask = UIBackgroundTaskInvalid;
    bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [[UIApplication sharedApplication] endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
    [self Fetchdata:notifId:senderId];
    [[UIApplication sharedApplication] endBackgroundTask:(UIBackgroundTaskIdentifier)bgTask];
    bgTask = UIBackgroundTaskInvalid;
    if(state == UIApplicationStateInactive)
    {
        JAVA_OBJECT str = fromNSString(CN1_THREAD_GET_STATE_PASS_ARG notifId);
        your_namespace_iosPushReceived___java_lang_String(CN1_THREAD_GET_STATE_PASS_ARG str);
    }
    completionHandler(UIBackgroundFetchResultNewData);
}
}

-(void)Fetchdata:(NSString*)notifId:(NSString*)senderId
{
NSURLSessionConfiguration *defaultSessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration:defaultSessionConfiguration];
NSURL *url = [NSURL URLWithString:@"https://.../"];
NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
NSString *postParams = [NSString stringWithFormat:@"%@%@%@%@%@", @"{\"notifId\":\"", notifId, @"\",\"senderId\":\"",senderId,@"\"}"];
NSData *postData = [postParams dataUsingEncoding:NSUTF8StringEncoding];
[urlRequest setHTTPMethod:@"POST"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[urlRequest setValue:[NSString stringWithFormat:@"%d", [postData length]] forHTTPHeaderField:@"Content-Length"];
[urlRequest setHTTPBody:postData];
NSURLSessionDataTask *dataTask = [defaultSession dataTaskWithRequest:urlRequest completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
}];
[dataTask resume];
}

[javieranton-zz]

I realise my previous answer is a bit too much for the OP. The OP doesn't want to stop using CN1 push, but to allow background processing with CN1 push. To continue using CN1's push but execute a bg task, include the following in the delegate's - (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler { (need to open sources with xCode and compile from there)

__block UIBackgroundTaskIdentifier bgTask = UIBackgroundTaskInvalid;
bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
    [[UIApplication sharedApplication] endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];
[self Fetchdata:notifId:senderId];
[[UIApplication sharedApplication] endBackgroundTask:(UIBackgroundTaskIdentifier)bgTask];
bgTask = UIBackgroundTaskInvalid;

This will execute a bg task as soon as the notif is received. You can persist things in NSUserDefaults. In the example in my previous answer, FetchData calls a WS from the background as soon as the notification arrives. FetchData would need to be included in ios.glAppDelegateBody build hint

@shannah maybe it would be worth creating a new build hint so others can include bg native code within didReceiveRemoteNotification:completionhandler, I don't know