Cannot handle push notifications

Question

I have a Xamarin.Forms app that uses push notifications. For Android, the following line:

(App.Current.MainPage as MainPage)?.AddMessage(body);

that is called from Android native OnMessageReceived(), throws NullReferenceException.

Why can this happen? Isn't App.Current to be accessible from the platform-specific project?

Here is the full OnMessageReceived() code:

    public override void OnMessageReceived(RemoteMessage message)
    {
        base.OnMessageReceived(message);
        string messageBody;

        if (message.GetNotification() != null)
        {
            messageBody = message.GetNotification().Body;
        }

        // NOTE: test messages sent via the Azure portal will be received here
        else
        {
            messageBody = message.Data.Values.First();
        }

        // convert the incoming message to a local notification
        SendLocalNotification(messageBody);

        // send the incoming message directly to the MainPage
        SendMessageToMainPage(messageBody); // THIS IS THE METHOD WHERE THE PROBLEMATIC LINE IS 
    }

I also tried to use MessagingCenter instead, like this:

        public override void OnMessageReceived(RemoteMessage message)
        {
            base.OnMessageReceived(message);
            string messageBody;

            if (message.GetNotification() != null)
            {
                messageBody = message.GetNotification().Body;
            }

            // NOTE: test messages sent via the Azure portal will be received here
            else
            {
                messageBody = message.Data.Values.First();
            }

            // convert the incoming message to a local notification
            SendLocalNotification(messageBody);

            // send the incoming message directly to the MainPage
            MessagingCenter.Send<object>(this, "newCall");

 //           SendMessageToMainPage(messageBody);
        }

But this message is never caught in the shared project's MainPage.xaml.cs.

Same issue with iOS, where I tried to send message from AppDelegate's DidReceiveRemoteNotification()...
Please help.

Answer 1

Hello,

Welcome to Microsoft Q&A!

The NullReferenceException shows App.Current.MainPage as MainPage is null in this scenario , please check if you set it correctly in App.cs .

However I suggest you move the logic into App.cs, the class always exists and would never be null.

Thank you.

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