如何在 iOS 上显示使用 firebase-cpp-sdk 收到的 FCM“数据”消息？

Question

I need to display a notification when my app is in background or killed. I have no problem to display FCM 'notification' message on iOS using firebase-cpp-sdk, I tried quickstart-cpp/messaging/testapp and it just worked. But when 'data' message is received when app is in background or foreground - no notification is displayed, I just see it in the log that message is received.

I use "content_available": true in message as suggested by many answers. This helps to actually receive the 'data' message, as I can see in the log, but the message is not displayed. I tried legacy HTTP and HTTP v1 protocols, the result is the same. An example of legacy HTTP message is:

{
    "data": {
        "body": "Entrance door Intrusion at 2 Jun 2020 01:32:08",
        "title": "Intrusion"
    },
    "content_available": true,
    "to": "fcm_device_token_here"
}

Do I need to manually create a notification like on Android? Or there are some other ways to do it?

Answer 1

To asnwer my own question - yes, I created a local notification. For that I used qt-notification library since I am using QT, but the code example to show notification is the following (taken from the project):

// create content
UNMutableNotificationContent *content = [[UNMutableNotificationContent alloc] init];
content.title = title.toNSString(); // your title
content.body = caption.toNSString(); // your notification text
content.sound = !sound.isEmpty() ? [UNNotificationSound soundNamed: sound.toNSString()] : [UNNotificationSound defaultSound]; // your sound
// content.sound = [UNNotificationSound criticalSoundNamed: sound.toNSString() withAudioVolume: 1.0]; // For that you need Apple's permission
content.badge = @([[UIApplication sharedApplication] applicationIconBadgeNumber] + 1);

// create trigger time
UNTimeIntervalNotificationTrigger *trigger = [UNTimeIntervalNotificationTrigger triggerWithTimeInterval:1 repeats:NO];

// unique identifier
NSString* identifierNSString = identifier.toNSString();

// create notification request
UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:identifierNSString
        content:content trigger:trigger];

// add request
UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
center.delegate = id(m_Delegate);

[center addNotificationRequest:request withCompletionHandler:^(NSError * _Nullable error) {
    if (error) {
        NSLog(@"Local Notification failed");
    }
}];