将MahApps.Metro风格应用于NavigationWindow

有人在NavigationWindow中应用了MahApps.Metro风格吗？我已经为Window实现了它，但需要将它应用于具有Pages的NavigationWindow。我试着扩展NavigationWindow并添加MetroWindow中的修改，但没有成功。"窗口"有一个标准的标题栏和边框，内容完全是黑色的。

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Navigation;
using MahApps.Metro.Native;
namespace MahApps.Metro.Controls
{
    [TemplatePart(Name = PART_TitleBar, Type = typeof(UIElement))]
    [TemplatePart(Name = PART_WindowCommands, Type = typeof(WindowCommands))]
    public class MetroNavigationWindow : NavigationWindow
    {
        private const string PART_TitleBar = "PART_TitleBar";
        private const string PART_WindowCommands = "PART_WindowCommands";
        public static readonly DependencyProperty ShowIconOnTitleBarProperty = DependencyProperty.Register("ShowIconOnTitleBar", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty ShowTitleBarProperty = DependencyProperty.Register("ShowTitleBar", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty ShowMinButtonProperty = DependencyProperty.Register("ShowMinButton", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty ShowCloseButtonProperty = DependencyProperty.Register("ShowCloseButton", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty ShowMaxRestoreButtonProperty = DependencyProperty.Register("ShowMaxRestoreButton", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty TitlebarHeightProperty = DependencyProperty.Register("TitlebarHeight", typeof(int), typeof(MetroNavigationWindow), new PropertyMetadata(30));
        public static readonly DependencyProperty TitleCapsProperty = DependencyProperty.Register("TitleCaps", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        public static readonly DependencyProperty SaveWindowPositionProperty = DependencyProperty.Register("SaveWindowPosition", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(false));
        public static readonly DependencyProperty WindowPlacementSettingsProperty = DependencyProperty.Register("WindowPlacementSettings", typeof(IWindowPlacementSettings), typeof(MetroNavigationWindow), new PropertyMetadata(null));
        public static readonly DependencyProperty TitleForegroundProperty = DependencyProperty.Register("TitleForeground", typeof(Brush), typeof(MetroNavigationWindow));
        public static readonly DependencyProperty IgnoreTaskbarOnMaximizeProperty = DependencyProperty.Register("IgnoreTaskbarOnMaximize", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(false));
        public static readonly DependencyProperty GlowBrushProperty = DependencyProperty.Register("GlowBrush", typeof(SolidColorBrush), typeof(MetroNavigationWindow), new PropertyMetadata(null));
        public static readonly DependencyProperty FlyoutsProperty = DependencyProperty.Register("Flyouts", typeof(FlyoutsControl), typeof(MetroNavigationWindow), new PropertyMetadata(null));
        public static readonly DependencyProperty WindowTransitionsEnabledProperty = DependencyProperty.Register("WindowTransitionsEnabled", typeof(bool), typeof(MetroNavigationWindow), new PropertyMetadata(true));
        bool isDragging;
        public bool WindowTransitionsEnabled
        {
            get { return (bool)this.GetValue(WindowTransitionsEnabledProperty); }
            set { SetValue(WindowTransitionsEnabledProperty, value); }
        }
        public FlyoutsControl Flyouts
        {
            get { return (FlyoutsControl)GetValue(FlyoutsProperty); }
            set { SetValue(FlyoutsProperty, value); }
        }
        public WindowCommands WindowCommands { get; set; }
        public bool IgnoreTaskbarOnMaximize
        {
            get { return (bool)this.GetValue(IgnoreTaskbarOnMaximizeProperty); }
            set { SetValue(IgnoreTaskbarOnMaximizeProperty, value); }
        }
        public Brush TitleForeground
        {
            get { return (Brush)GetValue(TitleForegroundProperty); }
            set { SetValue(TitleForegroundProperty, value); }
        }
        public bool SaveWindowPosition
        {
            get { return (bool)GetValue(SaveWindowPositionProperty); }
            set { SetValue(SaveWindowPositionProperty, value); }
        }
        public IWindowPlacementSettings WindowPlacementSettings
        {
            get { return (IWindowPlacementSettings)GetValue(WindowPlacementSettingsProperty); }
            set { SetValue(WindowPlacementSettingsProperty, value); }
        }
        public bool ShowIconOnTitleBar
        {
            get { return (bool)GetValue(ShowIconOnTitleBarProperty); }
            set { SetValue(ShowIconOnTitleBarProperty, value); }
        }
        public bool ShowTitleBar
        {
            get { return (bool)GetValue(ShowTitleBarProperty); }
            set { SetValue(ShowTitleBarProperty, value); }
        }
        public bool ShowMinButton
        {
            get { return (bool)GetValue(ShowMinButtonProperty); }
            set { SetValue(ShowMinButtonProperty, value); }
        }
        public bool ShowCloseButton
        {
            get { return (bool)GetValue(ShowCloseButtonProperty); }
            set { SetValue(ShowCloseButtonProperty, value); }
        }
        public int TitlebarHeight
        {
            get { return (int)GetValue(TitlebarHeightProperty); }
            set { SetValue(TitlebarHeightProperty, value); }
        }
        public bool ShowMaxRestoreButton
        {
            get { return (bool)GetValue(ShowMaxRestoreButtonProperty); }
            set { SetValue(ShowMaxRestoreButtonProperty, value); }
        }
        public bool TitleCaps
        {
            get { return (bool)GetValue(TitleCapsProperty); }
            set { SetValue(TitleCapsProperty, value); }
        }
        public SolidColorBrush GlowBrush
        {
            get { return (SolidColorBrush)GetValue(GlowBrushProperty); }
            set { SetValue(GlowBrushProperty, value); }
        }
        public string WindowTitle
        {
            get { return TitleCaps ? Title.ToUpper() : Title; }
        }
        public MetroNavigationWindow()
        {
            Loaded += this.MetroWindow_Loaded;
        }
        private void MetroWindow_Loaded(object sender, RoutedEventArgs e)
        {
            VisualStateManager.GoToState(this, "AfterLoaded", true);
            if (!ShowTitleBar)
            {
                //Disables the system menu for reasons other than clicking an invisible titlebar.
                IntPtr handle = new WindowInteropHelper(this).Handle;
                UnsafeNativeMethods.SetWindowLong(handle, UnsafeNativeMethods.GWL_STYLE, UnsafeNativeMethods.GetWindowLong(handle, UnsafeNativeMethods.GWL_STYLE) & ~UnsafeNativeMethods.WS_SYSMENU);
            }
            if (this.Flyouts == null)
            {
                this.Flyouts = new FlyoutsControl();
            }
        }
        static MetroNavigationWindow()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(MetroNavigationWindow), new FrameworkPropertyMetadata(typeof(MetroNavigationWindow)));
        }
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            if (WindowCommands == null)
                WindowCommands = new WindowCommands();
            var titleBar = GetTemplateChild(PART_TitleBar) as UIElement;
            if (ShowTitleBar && titleBar != null)
            {
                titleBar.MouseDown += TitleBarMouseDown;
                titleBar.MouseUp += TitleBarMouseUp;
                titleBar.MouseMove += TitleBarMouseMove;
            }
            else
            {
                MouseDown += TitleBarMouseDown;
                MouseUp += TitleBarMouseUp;
                MouseMove += TitleBarMouseMove;
            }
        }
        protected override void OnStateChanged(EventArgs e)
        {
            if (WindowCommands != null)
            {
                WindowCommands.RefreshMaximiseIconState();
            }
            base.OnStateChanged(e);
        }
        protected void TitleBarMouseDown(object sender, MouseButtonEventArgs e)
        {
            var mousePosition = e.GetPosition(this);
            bool isIconClick = ShowIconOnTitleBar && mousePosition.X <= TitlebarHeight && mousePosition.Y <= TitlebarHeight;
            if (e.ChangedButton == MouseButton.Left)
            {
                if (isIconClick)
                {
                    if (e.ClickCount == 2)
                    {
                        Close();
                    }
                    else
                    {
                        ShowSystemMenuPhysicalCoordinates(this, PointToScreen(new Point(0, TitlebarHeight)));
                    }
                }
                else
                {
                    IntPtr windowHandle = new WindowInteropHelper(this).Handle;
                    UnsafeNativeMethods.ReleaseCapture();
                    var wpfPoint = PointToScreen(Mouse.GetPosition(this));
                    short x = Convert.ToInt16(wpfPoint.X);
                    short y = Convert.ToInt16(wpfPoint.Y);
                    int lParam = x | (y << 16);
                    UnsafeNativeMethods.SendMessage(windowHandle, Constants.WM_NCLBUTTONDOWN, Constants.HT_CAPTION, lParam);
                    if (e.ClickCount == 2 && (ResizeMode == ResizeMode.CanResizeWithGrip || ResizeMode == ResizeMode.CanResize))
                    {
                        WindowState = WindowState == WindowState.Maximized ? WindowState.Normal : WindowState.Maximized;
                    }
                }
            }
            else if (e.ChangedButton == MouseButton.Right)
            {
                ShowSystemMenuPhysicalCoordinates(this, PointToScreen(mousePosition));
            }
        }
        protected void TitleBarMouseUp(object sender, MouseButtonEventArgs e)
        {
            isDragging = false;
        }
        private void TitleBarMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton != MouseButtonState.Pressed)
            {
                isDragging = false;
            }
            if (isDragging
                && WindowState == WindowState.Maximized
                && ResizeMode != ResizeMode.NoResize)
            {
                // Calculating correct left coordinate for multi-screen system.
                Point mouseAbsolute = PointToScreen(Mouse.GetPosition(this));
                double width = RestoreBounds.Width;
                double left = mouseAbsolute.X - width / 2;
                // Check if the mouse is at the top of the screen if TitleBar is not visible
                if (!ShowTitleBar && mouseAbsolute.Y > TitlebarHeight)
                    return;
                // Aligning window's position to fit the screen.
                double virtualScreenWidth = SystemParameters.VirtualScreenWidth;
                left = left + width > virtualScreenWidth ? virtualScreenWidth - width : left;
                var mousePosition = e.MouseDevice.GetPosition(this);
                // When dragging the window down at the very top of the border,
                // move the window a bit upwards to avoid showing the resize handle as soon as the mouse button is released
                Top = mousePosition.Y < 5 ? -5 : mouseAbsolute.Y - mousePosition.Y;
                Left = left;
                // Restore window to normal state.
                WindowState = WindowState.Normal;
            }
        }
        internal T GetPart<T>(string name) where T : DependencyObject
        {
            return (T)GetTemplateChild(name);
        }
        private static void ShowSystemMenuPhysicalCoordinates(Window window, Point physicalScreenLocation)
        {
            if (window == null) return;
            var hwnd = new WindowInteropHelper(window).Handle;
            if (hwnd == IntPtr.Zero || !UnsafeNativeMethods.IsWindow(hwnd))
                return;
            var hmenu = UnsafeNativeMethods.GetSystemMenu(hwnd, false);
            var cmd = UnsafeNativeMethods.TrackPopupMenuEx(hmenu, Constants.TPM_LEFTBUTTON | Constants.TPM_RETURNCMD, (int)physicalScreenLocation.X, (int)physicalScreenLocation.Y, hwnd, IntPtr.Zero);
            if (0 != cmd)
                UnsafeNativeMethods.PostMessage(hwnd, Constants.SYSCOMMAND, new IntPtr(cmd), IntPtr.Zero);
        }
    }
}