Xamarin-推送通知，OnMessageReceived触发多次，加载多个页面

Question

有问题的人，

我想加载一个显示推送通知字符串内容的页面，但是触发OnReceivedMessage（）的次数越来越多，这等于我进入DisplayPage并返回的次数。

因此，我第一次运行时，OnRevceivedMessage触发器会打开我关闭的DisplayPage（）并通过PopAsync（）返回上一页。我第二次使用Postman发送通知，并执行一个循环来加载DisplayNotificationPage，然后返回，OnReceivedMessage（）触发两次，然后每次运行触发3次，等等。

这是怎么回事？我认为它与订阅有关。.我该如何解决？

[XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class NotificationReceivingPage : ContentPage
    {
        public NotificationReceivingPage ()
        {
            InitializeComponent ();
        }


        protected override void OnAppearing()
        {
            base.OnAppearing();
            MessagingCenter.Subscribe<object, string>(this, App.NotificationReceivedKey, OnMessageReceived);
        }

        private void OnMessageReceived(object sender, string incomingNotificationBody)     // gets triggered x1, x2, x3... and so on
        {
            if (!string.IsNullOrEmpty(incomingNotificationBody))
            {
                Navigation.PushAsync(new NotificationDisplayPage(incomingNotificationBody));
            }         
        }

        protected override void OnDisappearing()
        {
            base.OnDisappearing();
            MessagingCenter.Unsubscribe<object>(this, App.NotificationReceivedKey);
        }


[XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class NotificationDisplayPage : ContentPage
    {
        ISimpleAudioPlayer soundPlayer;
        private static string incomingMessage = null;

        //default constructor
        public AlarmDisplayPage ()
        {
            InitializeComponent ();
        }

        // overloaded constructor that receives incoming notification body
        public AlarmDisplayPage(string messageBody)
        {
            InitializeComponent();

            if (messageBody != null)
            {
                incomingMessage = messageBody;
            }

            //alarm to sound on incoming message
            var assembly = typeof(AlarmDisplayPage);
            alertHeader.Source = ImageSource.FromResource("ShakeAlarmRR1.Assets.Images.test-event-header.png", assembly);
        }


        protected override void OnAppearing()
        {
            base.OnAppearing();

            stopAlarmButton.IsEnabled = true;

            //initialize soundplayer
            soundPlayer = Plugin.SimpleAudioPlayer.CrossSimpleAudioPlayer.Current;
            soundPlayer.Load(GetStreamFromFile("alarm.mp3"));

            if (!string.IsNullOrEmpty(incomingMessage))
            {
                setEventDetails();

                //play the alarm
                soundPlayer.Play();
            }    

        }

        protected override void OnDisappearing()
        {
            base.OnDisappearing();
            soundPlayer.Stop();
            incomingMessage = null;
        }


        private Stream GetStreamFromFile(string mediaFilename)
        {
            var assembly = typeof(App).GetTypeInfo().Assembly;
            var stream = assembly.GetManifestResourceStream("ShakeAlarmRR1.Assets.Sounds." + mediaFilename);
            return stream;
        }

        private void stopAlarmButton_Clicked(object sender, EventArgs e)
        {
            stopAlarmButton.IsEnabled = false;

            Navigation.PopToRootAsync();
        }

        private void setEventDetails()
        {
            if (!string.IsNullOrEmpty(incomingMessage))
            {
                labelEventType.Text = incomingMessage;
            }
            else
            {
                labelEventType.Text = "No Data";
            }

        }
    }