FirstView.xaml.cs

using Windows.Foundation;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using MvvmCrossUWP.Core.ViewModels;

namespace MvvmCrossUWP.Win.Views
{
	public sealed partial class FirstView : BaseView
	{
        public static FirstView Current = null;
        public Frame AppFrame { get { return (Frame)this.WrappedFrame.UnderlyingControl; } }

        public FirstViewModel Vm => (FirstViewModel)ViewModel;

        public FirstView()
		{
			this.InitializeComponent();

            this.Loaded += (sender, args) =>
            {
                Current = this;

                this.TogglePaneButton.Focus(FocusState.Programmatic);
            };

            this.RootSplitView.RegisterPropertyChangedCallback(
                SplitView.DisplayModeProperty,
                (s, a) =>
                {
                    // Ensure that we update the reported size of the TogglePaneButton when the SplitView's
                    // DisplayMode changes.
                    this.CheckTogglePaneButtonSizeChanged();
                });

            SystemNavigationManager.GetForCurrentView().BackRequested += SystemNavigationManager_BackRequested;
        }

        private void SystemNavigationManager_BackRequested(object sender, BackRequestedEventArgs e)
        {
            if (!e.Handled && this.AppFrame.CanGoBack)
            {
                e.Handled = true;
                this.AppFrame.GoBack();
            }
        }

        public Rect TogglePaneButtonRect
        {
            get;
            private set;
        }

        /// <summary>
        /// An event to notify listeners when the hamburger button may occlude other content in the app.
        /// The custom "PageHeader" user control is using this.
        /// </summary>
        public event TypedEventHandler<FirstView, Rect> TogglePaneButtonRectChanged;

        /// <summary>
        /// Callback when the SplitView's Pane is toggled open or close.  When the Pane is not visible
        /// then the floating hamburger may be occluding other content in the app unless it is aware.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void TogglePaneButton_Checked(object sender, RoutedEventArgs e)
        {
            this.CheckTogglePaneButtonSizeChanged();
        }

        /// <summary>
        /// Check for the conditions where the navigation pane does not occupy the space under the floating
        /// hamburger button and trigger the event.
        /// </summary>
        private void CheckTogglePaneButtonSizeChanged()
        {
            if (this.RootSplitView.DisplayMode == SplitViewDisplayMode.Inline ||
                this.RootSplitView.DisplayMode == SplitViewDisplayMode.Overlay)
            {
                var transform = this.TogglePaneButton.TransformToVisual(this);
                var rect = transform.TransformBounds(new Rect(0, 0, this.TogglePaneButton.ActualWidth, this.TogglePaneButton.ActualHeight));
                this.TogglePaneButtonRect = rect;
            }
            else
            {
                this.TogglePaneButtonRect = new Rect();
            }

            var handler = this.TogglePaneButtonRectChanged;
            if (handler != null)
            {
                // handler(this, this.TogglePaneButtonRect);
                handler.DynamicInvoke(this, this.TogglePaneButtonRect);
            }
        }

    }
}