How do I detect when a modal page disappears?

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PatrickRyder asked Feb 9, '21 PatrickRyder commented Mar 23, '21

How do I detect when a modal page disappears?

When a Page is displayed, its OnAppearing() function is called. If I then push another non-modal page and then, on this new page, navigate back to the parent, its OnAppearing() function is called again.

If I now do the same but push a modal page, when I pop from this modal page, is there an easy way to detect the disappearance of the modal page back in the 'parent' page?

I am aware that the modal and non-modal pages use different stacks and so the 'parent' page is not a true parent but this seems like a fairly reasonable event to need to hook onto, so I wondered if there was an accepted way of doing this?

Any help would be welcome.

Kind wishes - Patrick

dotnet-xamarin

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Answer 1 · 2021-02-09T12:33:02.027Z

LeonLu-MSFT answered Feb 9, '21 PatrickRyder commented Mar 23, '21

Hello,

Welcome to our Microsoft Q&A platform!

You can create a public static Stack in the MainPage. After you Navigation.PushModalAsync(new Page1());, you can push a value to Stack with NavigationStack.Push("MainPage");, If you Navigation.PopModalAsync(); in the Page1, MainPage's OnAppearing method will execute, you can check the value. You can check the stack in other page as well.

Please refer to the following link.

static  Stack NavigationStack;
        public MainPage()
        {
            NavigationStack = new Stack();
          
            InitializeComponent();
            BindingContext = this;


            
          

        }

        private void Button_Clicked(object sender, EventArgs e)
        {

            Navigation.PushModalAsync(new Page1());
            NavigationStack.Push("MainPage");
        }

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

            if (NavigationStack.Contains("MainPage"))
            {
                DisplayAlert("info","you back","OK");
            }
        }

Best Regards,

Leon Lu

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PatrickRyder · Mar 23, 2021 at 09:55 AM

@LeonLu-MSFT

Is there any way to detect if the user simply taps the back-navigation link at the top of the page?

Patrick

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