The OnAppearing() issue with Navigation.PushAsync()

[Billycool1020]

Description

In main page use a button call Navigation.PushAsync(new Page1()) to open Page1. The OnAppearing() in Page1 fired again immediately if I call the Device.OpenUri(new Uri("https://github.com/")) in the OnAppearing(). But if I set a breakpoint or set Task.Delay(500) before the Device.OpenUri(), second OnAppearing() will not fired until I get back from the browser. The similiar issue also happens when call Navigation.PushAsync() in the OnAppearing().

Steps to Reproduce

1. The App.cs:

		public App ()
		{
			InitializeComponent();
			MainPage = new NavigationPage(new MainPage());
		}

2. MainPage

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"           
             x:Class="App1.MainPage">
    <StackLayout>
        <!-- Place new controls here -->
        <Button Text="Page 1" x:Name="button" Clicked="button_Clicked"/>
    </StackLayout>
</ContentPage>

	public partial class MainPage : ContentPage
	{
		public MainPage()
		{
			InitializeComponent();
		}
                private void button_Clicked(object sender, EventArgs e)
                {
                    Navigation.PushAsync(new Page1());
                }
       }

3. Page1

	public partial class Page1 : ContentPage
	{
		public Page1 ()
		{
			InitializeComponent ();
       		 }
      		 protected override  void OnAppearing()
    		 {   
                        base.OnAppearing();
                        Device.OpenUri(new Uri("https://github.com/"));
                 }
         }

Expected Behavior

OnAppearing() fired and open one tab in the browser.

Actual Behavior

OnAppearing() fired twice and open two tabs in the browser. If I set a breakpoint or set Task.Delay(500) before the Device.OpenUri();, second OnAppearing() will not fired immediately .

Basic Information

• IDE: Visual Studio Enterprise 2017 15.7.1
• Platform Target Frameworks:
  • Android: 8.1

[pauldipietro]

The described behavior appears to occur as of the 3.1-pre on an 8.1 emulator.

[VahidShir]

I have this problem in Xamarin.Forms "2.5.1.527436" and on both emulator and device.

[PureWeen]

Consolidating OnAppearing issues here
#6919