bitwarden-android/src/App/App.xaml.cs

using Bit.App.Pages;
using Bit.App.Utilities;
using System;
using System.Reflection;
using Xamarin.Forms;
using Xamarin.Forms.StyleSheets;
using Xamarin.Forms.Xaml;

[assembly: XamlCompilation(XamlCompilationOptions.Compile)]
namespace Bit.App
{
    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();

            ThemeManager.SetTheme("dark");
            MainPage = new TabsPage();
        }

        protected override void OnStart()
        {
            // Handle when your app starts
        }

        protected override void OnSleep()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume()
        {
            // Handle when your app resumes
        }
    }
}