Xamarin.FormsでOnSleep・OnResumeをViewModelでハンドルする

App.xaml.cs

public partial class App : Application
{
    .....

    protected override void OnSleep()
    {
        (MainPage.BindingContext as IApplicationLifecycle)?.OnSleep();
    }

    protected override void OnResume()
    {
        (MainPage.BindingContext as IApplicationLifecycle)?.OnResume();
    }
}

IApplicationLifecycle.cs

public interface IApplicationLifecycle
{
    void OnSleep();
    void OnResume();
}

MainPageViewModel.cs

public class MainPageViewModel : IApplicationLifecycle
{
    public void OnSleep()
    {
    }

    public void OnResume()
    {
    }
}