Xamarin.Forms: Change Icon & Text size in TabbedPage tabs

In your Android project's Resources/values/style.xml file, you can create a style:

<style name="MyTabTextStyle" parent="Base.Widget.Design.TabLayout">
    <item name="android:textSize">8sp</item>
</style>

And then in your Resources/layout/tabs.axml file, you can use the style:

<android.support.design.widget.TabLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    ... other attributes ...
    app:tabTextAppearance="@style/MyTabTextStyle" />

As for the icon, try this: https://stackoverflow.com/a/46465233/3183946

And by the way, I think "Dairy" should be "Diary" in your app

After some effort i get it work for android using TabbedPageRenderer. Created custom layout with ImageView & TetxtView below Custom_tab_layou.xaml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="41dp"
    android:orientation="vertical">
    <ImageView
        android:id="@+id/icon"
        android:layout_width="18dp"
        android:layout_height="18dp"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="4dp"
        android:layout_marginBottom="4dp" />
    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="hello"
        android:gravity="center"
        android:textSize="11dp"
        android:textColor="#00FF6F" />
</LinearLayout>

Created MyTabbedPageRenderer class

    public class MyTabbedPageRenderer : TabbedPageRenderer
    {
        private Dictionary<Int32, Int32> icons = new Dictionary<Int32, Int32>();
        bool setup;
        ViewPager pager;
        TabLayout layout;
        public MyTabbedPageRenderer(Context context) : base(context)
        {
        }

        protected override void SetTabIcon(TabLayout.Tab tab, FileImageSource icon)
        {
            base.SetTabIcon(tab, icon);
            tab.SetCustomView(Resource.Layout.Custom_tab_layou);

            var imageview = tab.CustomView.FindViewById<ImageView>(Resource.Id.icon);
            var tv = tab.CustomView.FindViewById<TextView>(Resource.Id.tv);

            tv.SetText(tab.Text, TextView.BufferType.Normal);
            imageview.SetBackgroundDrawable(tab.Icon);

            ColorStateList colors2 = null;

            if ((int)Build.VERSION.SdkInt >= 23)
                colors2 = Resources.GetColorStateList(Resource.Color.icon_tab, Forms.Context.Theme);
            else
                colors2 = Resources.GetColorStateList(Resource.Color.icon_tab);
            tv.SetTextColor(colors2);
        }

        //this is for changing text color of select tab
        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);
            if (setup)
                return;
            if (e.PropertyName == "Renderer")
            {
                pager = (ViewPager)ViewGroup.GetChildAt(0);
                layout = (TabLayout)ViewGroup.GetChildAt(1);
                setup = true;
                ColorStateList colors = null;

                if ((int)Build.VERSION.SdkInt >= 23)
                    colors = Resources.GetColorStateList(Resource.Color.icon_tab, Forms.Context.Theme);
                else
                    colors = Resources.GetColorStateList(Resource.Color.icon_tab);

                for (int i = 0; i < layout.TabCount; i++)
                {
                    var tab = layout.GetTabAt(i);
                    var icon = tab.Icon;

                    Android.Views.View view = GetChildAt(i);
                    if (view is TabLayout) layout = (TabLayout)view;

                    if (icon != null)
                    {
                        icon = Android.Support.V4.Graphics.Drawable.DrawableCompat.Wrap(icon);
                        Android.Support.V4.Graphics.Drawable.DrawableCompat.SetTintList(icon, colors);
                    }
                }
            }
        }
  }