How can you restrict/control the navigation routes the user can visit based on login status/role?

问题

For my Xamarin.Forms app, I am looking for a way to check if a user has the right role/authentication status to access a page. I know Angular has route guards that can be reused for different routes to check for an authentication status. Is there something similar in Xamarin.Forms?

回答1:

Here is an example showing how you can control the visibility or navigation to your pages based on the login status of the user.

By default Shell will always displays initially the first element defined in AppShell.xaml, in this case it will be Login.xaml page.

In the below example "Page3" will be visible initially because by default (Isvisible=true), while "Page2" it will only be visible when the bindable property IsLogged is true.

• You can handle any logic when user Log in/Log out in the IsLogged_PropertyChanged() event.

• If you want several/specific or page based roles you can always create/define/design yours, use them in bindings, raise and use their property changed event to execute actions.

---

With FlyoutItem

AppShell.xaml

<Shell Shell.FlyoutBehavior="Disabled"..>
   <FlyoutItem FlyoutDisplayOptions="AsMultipleItems">
        <Tab>
            <ShellContent Title="Login" Route="Login">
                <local:Login />
            </ShellContent>

            <ShellContent Title="Page2" Route="Page2"
                ContentTemplate="{DataTemplate local:Page2}"
                IsVisible="{Binding IsLogged}"/>

            <ShellContent Title="Page3" Route="Page3"
                ContentTemplate="{DataTemplate local:Page3}"/>
        </Tab>
    </FlyoutItem>

AppShell.xaml.cs

public bool IsLogged
{
    get => (bool)GetValue(IsLoggedProperty);
    set => SetValue(IsLoggedProperty, value);
}

public static readonly BindableProperty IsLoggedProperty =
    BindableProperty.Create("IsLogged", typeof(bool), typeof(AppShell), false, propertyChanged: IsLogged_PropertyChanged);

private static void IsLogged_PropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
//handle log in/log out event
    if ((bool) newValue)
       //user just logged in logic
    else
      //user just logged out logic
}

Login.xaml

<StackLayout>
    <Label
        FontSize="45"
        HorizontalOptions="FillAndExpand"
        Text="Login Page" />
    <Button Clicked="Button_Clicked" Text="Log In" />
</StackLayout>

Login.xaml.cs

private async void Button_Clicked(object sender, System.EventArgs e)
{
    IsVisible = false;                          //hide login page
    //Trigger the binding to show pages previously hidden
    (Shell.Current as AppShell).IsLogged = true;
    await Shell.Current.GoToAsync("//Page2");   //navigate to main page (next after log)
                                               //Enable the flyout: hamburger button
    Shell.Current.FlyoutBehavior = FlyoutBehavior.Flyout;  
}

---

Same thing with Tabs

In this example "Symbols" bottom tab won't be visible the same for upper tab "B" that belongs to bottom tab "Letters" until the user log-in, the remaining bottoms tabs will be visible initially.

AppShell.xaml

<TabBar>
    <ShellContent Title="Login" Route="Login">
        <local:Login />
    </ShellContent>

    <Tab Title="Letters">
        <ShellContent
            Title="A"
            ContentTemplate="{DataTemplate local:Page1}"
            Route="Page1" />

        <ShellContent
            Title="B"
            ContentTemplate="{DataTemplate local:Page2}"
            IsVisible="{Binding IsLogged}"
            Route="Page2" />

        <ShellContent
            Title="C"
            ContentTemplate="{DataTemplate local:Page3}"
            Route="Page3" />
    </Tab>

    <Tab Title="Digits">
        <ShellContent
            Title="100"
            ContentTemplate="{DataTemplate local:Page4}"
            Route="Page4" />
    </Tab>

    <Tab Title="Symbols" IsVisible="{Binding IsLogged}">
        <ShellContent
            Title="!"
            ContentTemplate="{DataTemplate local:Page5}"
            Route="Page5" />
    </Tab>
</TabBar>

来源：https://stackoverflow.com/questions/65186262/how-can-you-restrict-control-the-navigation-routes-the-user-can-visit-based-on-l