如何在Android: Xamarin Forms中更改选项卡式页面标题的选定和未选定颜色

<?xml version="1.0" encoding="UTF-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <style name="CustomTabLayout" parent="Widget.Design.TabLayout">
        <item name="tabIndicatorColor">@color/selected_tab_color</item>
        <item name="tabTextAppearance">@style/CustomTabTextAppearance</item>
    </style>

    <style name="CustomTabTextAppearance" parent="TextAppearance.Design.Tab">
        <item name="android:textColor">@color/unselected_tab_color</item>
        <item name="android:textSize">14sp</item>
        <item name="android:textStyle">bold</item>
    </style>
</resources>

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);

    // ...

    TabLayoutResource = Resource.Layout.Tabbar;
    ToolbarResource = Resource.Layout.Toolbar;

    // 应用自定义的TabLayout样式
    TabLayoutResource = Resource.Layout.Tabbar;
    TabLayout.TabLayoutBehavior = TabLayoutMode.Fixed;
    TabLayout.TabGravity = TabLayoutGravity.Fill;
    TabLayout.TabTextColors = ColorStateList.ValueOf(Android.Graphics.Color.White);
    TabLayout.SetTabTextColors(Android.Graphics.Color.ParseColor("#999999"), Android.Graphics.Color.ParseColor("#ffffff"));
    TabLayout.SetSelectedTabIndicatorColor(Android.Graphics.Color.ParseColor("#ffffff"));
    TabLayout.SetTabTextColors(Android.Graphics.Color.ParseColor("#999999"), Android.Graphics.Color.ParseColor("#ffffff"));
    TabLayout.SetBackgroundResource(Resource.Drawable.tab_layout_background);
}

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- ... -->
    <item name="android:tabLayoutStyle">@style/CustomTabLayout</item>
</style>