Xamarin 导航问题

Question

I'm have an issue that I can not understand, I want to navigate from MainPage to another page (CheckPage), Then I want to back to the MainPage, Programmatly it's work but there is a white space from the top when I back to the MainPage, See the screenshot

MainPage Code

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="xamrinApp.MainPage">

<StackLayout>

    <Grid BackgroundColor="DimGray" HeightRequest="100">
        <Label Text="Xamarin App" FontSize="22" Margin="0,50,0,0" HorizontalTextAlignment="Center" TextColor="White"/>
    </Grid>

    <Label Text="Welcome to Xamarin application" FontSize="Title" Padding="30,10,30,10"/>
    <Label Text="Please select from the list:" FontSize="16" Padding="30,0,30,0"/>

    
    <Entry x:Name="enRegistrationNumber" Margin="10"></Entry>
   <Button x:Name="btnClickMe" Text="Fetch" Clicked="btnClickMe_Clicked" />

    <Label x:Name="laResult" Text="..." HorizontalTextAlignment="Center"></Label>

    <Button x:Name="btnCheckRecord" Text="Check Record" Clicked="btnCheckRecord_Clicked"/>

</StackLayout>

Check record button code

App.Current.MainPage  = new NavigationPage(new CheckRecordPage());

CheckRecord page code

<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="xamrinApp.Views.CheckRecordPage">

<Grid BackgroundColor="LightYellow">
    <Button x:Name="btnBack" Text="Back" Clicked="btnBack_Clicked"></Button>
</Grid>

Back button code

App.Current.MainPage = new NavigationPage(new MainPage());

Answer 1

That's not how navigation works. Please read the docs

when you first assign the MainPage in App.xaml.cs , wrap it in a NavigationPage

MainPage = new NavigationPage(new MyFirstPage());

then when you want to navigation from the first page to the second page

// in MyFirstPage
this.Navigation.PushAsync(new MySecondPage());

when you want to navigate back to the first page, your user can either use the back button, or you can do this programatically

// in MySecondPage
this.Navigation.PopAsync();

Answer 2

If you are using the AppShell try to navigate with:

Shell.Current.GoToAsync($"YourPageName");

Don't forget to register a route for your page in AppShell.xaml.cs in the constructor:

Routing.RegisterRoute(nameof(YourPageName) , typeof(YourPageName));