使用OneSignal从收到的通知中设置徽章值

Question

Whenever a message is sent between users (device to device), the receiving user gets a notification if the app is not in focus. Along with the notification, the badge value for that tab should increase by 1. In an attempt to do so, I've created a NotificationCenter action that goes off in OneSignal's handleNotificationReceived block (within initLaunchWithOptions ) like so:

handleNotificationReceived: { (notification) in
            //Notification
            NotificationCenter.default.post(name: MESSAGE_NOTIFICATION, object: nil)
            print("Received Notification - \(notification?.payload.notificationID ?? "")")
    }, 

and the observer is located within the Messaging tab with a function that increases the tab bar badge:

NotificationCenter.default.addObserver(self, selector: #selector(addBadge), name: MESSAGE_NOTIFICATION, object: nil)

//Adds a badge to the messages bar
func addBadge(){
    self.navigationController?.tabBarController?.tabBar.items?[3].badgeValue = "1"
    if #available(iOS 10.0, *) {
        self.navigationController?.tabBarController?.tabBar.items?[3].badgeColor = ChatMessageCell.indexedColor
    } else {
        // Fallback on earlier versions
    }
}

However, Im still not able to get the badge value for the user to appear

Answer 1

It depends on how your view controller hierarchy is set up. The way you're trying to access badgeValue , it's likely that it's not being set because one of those optional properties is returning nil. Set a breakpoint on that line and inspect their values to learn which one.

If your view controller is embedded in a navigation controller and that navigation controller is the first child in the tab hierarchy, like

UITabBarController -> UINavigationController -> UIViewController

then from the UIViewController you could get to the badge value like this navigationController?.tabBarItem.badgeValue .

navigationController will return the nearest ancestor that is a UINavigationController. If that is the first child controller in the tab hierarchy then its tabBarItem property will return the UITabBarItem for the tab and you can update the badge value there.

//Adds a badge to the messages bar
func addBadge(){
    if let currentValue = navigationController?.tabBarItem.badgeValue {
        let newValue = Int(currentValue)! + 1
        navigationController?.tabBarItem.badgeValue = "\(newValue)"
    } else {
        navigationController?.tabBarItem.badgeValue = "1"
    }

    if #available(iOS 10.0, *) {
        navigationController?.tabBarItem.badgeColor = ChatMessageCell.indexedColor
    } else {
        // Fallback on earlier versions
    }
}