Xamarin.Forms：处理导航工具栏按钮（外壳）

Question

I want to handle any back clicks in my Xamarin.Forms application (android version).

For Android/hardware button was pretty easy, all I had to do was override OnBackButtonPressed method. But this top toolbar is not that easy. I heard that it should work with Shell.SetBackButtonBehavior, but for some reason, it doesn't work for me.

My code is like this, I put it in the page constructor after the InitializeComponents().

Shell.SetBackButtonBehavior(this, new BackButtonBehavior {
            Command = new Command(async () =>
                await Shell.Current.DisplayAlert("Back","Back","Back")
            )
        });

Any idea what could be wrong?

Answer 1

The function can be realized by defining Shell.BackButtonBehavior in xaml and implementing Command in cs.

Here is a small example of mine:

In xaml：

<Shell.BackButtonBehavior>
    <BackButtonBehavior Command="{Binding GoBack}" >
    </BackButtonBehavior>
</Shell.BackButtonBehavior>
<ContentPage.Content>
    <StackLayout>
        <Label Text="Welcome to Xamarin.Forms!"
            VerticalOptions="CenterAndExpand" 
            HorizontalOptions="CenterAndExpand" />
    </StackLayout>
</ContentPage.Content>

In cs:

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Page2 : ContentPage
{
    public ICommand GoBack { get; set; }
    public Page2()
    {
        InitializeComponent();
        GoBack = new Command(async () =>
            await Shell.Current.DisplayAlert("Back", "Back", "Back"));
        BindingContext = this;
    }
    
}