xamarin - 在Android上更改TabbedPage项目FontSize

你可以按照这个博客改变FontSize的tabbedPageAndroid上的项目，写custom renderer的TabbedPage和改变的textSize还有：

[assembly: ExportRenderer(typeof(ExtendedTabbedPage), typeof(ExtendedTabbedPageRenderer))]
namespace CustomTabbedPage.Droid
{
    public class ExtendedTabbedPageRenderer : TabbedPageRenderer
    {
        Xamarin.Forms.TabbedPage tabbedPage;
        BottomNavigationView bottomNavigationView;
        Android.Views.IMenuItem lastItemSelected;
        private bool firstTime = true;
        int lastItemId=-1;
        public ExtendedTabbedPageRenderer(Context context) : base(context)
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.TabbedPage> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
            {
                tabbedPage = e.NewElement as ExtendedTabbedPage;
                bottomNavigationView = (GetChildAt(0) as Android.Widget.RelativeLayout).GetChildAt(1) as BottomNavigationView;


                //Call to change the font
                ChangeFont();
            }
        }

        //Change Tab font
        void ChangeFont()
        {
            var fontFace = Typeface.CreateFromAsset(Context.Assets, "gilsansultrabold.ttf");
            var bottomNavMenuView = bottomNavigationView.GetChildAt(0) as BottomNavigationMenuView;

            for (int i = 0; i < bottomNavMenuView.ChildCount; i++)
            {
                var item = bottomNavMenuView.GetChildAt(i) as BottomNavigationItemView;
                var itemTitle = item.GetChildAt(1);

                var smallTextView = ((TextView)((BaselineLayout)itemTitle).GetChildAt(0));
                var largeTextView = ((TextView)((BaselineLayout)itemTitle).GetChildAt(1));

                lastItemId = bottomNavMenuView.SelectedItemId;

                //smallTextView.SetTypeface(fontFace, TypefaceStyle.Bold);
                //largeTextView.SetTypeface(fontFace, TypefaceStyle.Bold);

                smallTextView.TextSize = 18;
                largeTextView.TextSize = 18;

                //Set text color
                var textColor = (item.Id == bottomNavMenuView.SelectedItemId) ? tabbedPage.On<Xamarin.Forms.PlatformConfiguration.Android>().GetBarSelectedItemColor().ToAndroid() : tabbedPage.On<Xamarin.Forms.PlatformConfiguration.Android>().GetBarItemColor().ToAndroid();
                smallTextView.SetTextColor(textColor);
                largeTextView.SetTextColor(textColor);
            }
        }      
    }
}

改变textSize的smallTextView，并largeTextView会工作。您也可以在此处下载示例项目。