Xamarin Android TitleView losing custom font

Question

Something strange is happening, in my xamarin form application, my xaml pages have this custom titleview:

<Shell.TitleView>
    <Grid
        Margin="0,0,0,0"
        RowDefinitions="*" 
        ColumnDefinitions="*,*">
        <local1:AutoFitLabel
            x:Name="labelTitle"
            Grid.Column="0"
            Text="My page title"
            TextColor="{StaticResource TextGray}"
            FontSize="Title"
            VerticalTextAlignment="Center"
            VerticalOptions="Center"
            FontFamily="VisbyRegular"
            MaxLines="1">
        </local1:AutoFitLabel>
        <ImageButton 
            Clicked="ShowSearchPage"
            BackgroundColor="White"      
            Padding="{OnPlatform Android='14', iOS='7'}" 
            HorizontalOptions="End"
            Grid.Column="1"
            Source="search">
        </ImageButton>
    </Grid>
</Shell.TitleView>

Everyghing works as expected when the page shows up but, if switch to actual tab (Tab0) to another tab (Tab1) an then i go back to Tab0, the title of the page is shown with the system default font. "FontFamily="VisbyRegular"" is no longer taking effect.

This is happening only on Android, in iOS everything is working as expected.

I've also tried to force in the class in the on appearing method the custom font to "labelTitle" but with no effect on the label itself.

Is it a known issue or am i diong something wrong? Any way i can workaround this problem?

Thanks

Answer 1

As you can see in here https://github.com/xamarin/Xamarin.Forms/issues/14248 It is an open issue in xamarin.forms. You can try use the custom renderers :

[assembly: ExportRenderer(typeof(AppShell), typeof(MyShellRenderer))]
namespace App30.Droid
{
    public class MyShellRenderer : ShellRenderer
    {
        public MyShellRenderer(Context context) : base(context)
        {
        }

        protected override IShellBottomNavViewAppearanceTracker CreateBottomNavViewAppearanceTracker(ShellItem shellItem)
        {
            return new CustomBottomNavAppearance();
        }
    }

    public class CustomBottomNavAppearance : IShellBottomNavViewAppearanceTracker
    {
        public void Dispose()
        {

        }

        public void ResetAppearance(BottomNavigationView bottomView)
        {

        }

        public void SetAppearance(BottomNavigationView bottomView, ShellAppearance appearance)
        {

            IMenu menu = bottomView.Menu;
            for (int i = 0; i < bottomView.Menu.Size(); i++)
            {
                IMenuItem menuItem = menu.GetItem(i);
                var title = menuItem.TitleFormatted;
                SpannableStringBuilder sb = new SpannableStringBuilder(title);

                int a = sb.Length();
                
                //here I set fontsize 20
                sb.SetSpan(new AbsoluteSizeSpan(20,true), 0, a, SpanTypes.ExclusiveExclusive);

                menuItem.SetTitle(sb);
            }

        }
    }
}