maui-linux/Xamarin.Forms.Platform.WPF/FormsApplicationPage.cs

using System.ComponentModel;
using System.Windows;
using WpfLightToolkit.Controls;

namespace Xamarin.Forms.Platform.WPF
{
	public class FormsApplicationPage : LightWindow
	{
		protected Application Application { get; private set; }
		protected Platform Platform { get; private set; }
		
		public FormsApplicationPage()
		{
			System.Windows.Application.Current.Startup += OnLaunching;
			System.Windows.Application.Current.Exit += OnClosing;

			MessagingCenter.Send(this, WPFDeviceInfo.BWPorientationChangedName, this.ToDeviceOrientation());
			SizeChanged += OnOrientationChanged;

			this.ContentLoader = new FormsContentLoader();
		}

		public void LoadApplication(Application application)
		{
			Application.Current = application;
			application.PropertyChanged += ApplicationOnPropertyChanged;
			Application = application;

			// Hack around the fact that OnLaunching will haev already happened by this point, sad but needed.
			application.SendStart();
		}

		void ApplicationOnPropertyChanged(object sender, PropertyChangedEventArgs args)
		{
			if (args.PropertyName == "MainPage")
				SetMainPage();
		}

		void OnActivated(object sender, System.EventArgs e)
		{
			// TODO : figure out consistency of get this to fire
			// Check whether tombstoned (terminated, but OS retains information about navigation state and state dictionarys) or dormant
			Application.SendResume();
		}

		// when app gets tombstoned, user press back past first page
		async void OnClosing(object sender, ExitEventArgs e)
		{
			await Application.SendSleepAsync();
		}

		async void OnDeactivated(object sender, System.EventArgs e)
		{
			await Application.SendSleepAsync();
		}

		void OnLaunching(object sender, StartupEventArgs e)
		{
			Application.SendStart();
		}

		void OnOrientationChanged(object sender, SizeChangedEventArgs e)
		{
			MessagingCenter.Send(this, WPFDeviceInfo.BWPorientationChangedName, this.ToDeviceOrientation());
		}

		void SetMainPage()
		{
			if (Platform == null)
				Platform = new Platform(this);

			Platform.SetPage(Application.MainPage);
		}

		protected override void Appearing()
		{
			base.Appearing();
			SetMainPage();
		}

		public override void OnBackSystemButtonPressed()
		{
			Application.NavigationProxy.PopModalAsync();
		}
	}
}