Hide appbar when using SlideView

SlideViewFrame.cs

using System;
using System.Windows;
using Microsoft.Phone.Controls;
using System.Windows.Controls;

namespace SlideView.Library
{
    [TemplatePart(Name = SlideViewName, Type = typeof(SlideView))]
    public class SlideApplicationFrame : TransitionFrame
    {
        internal const string SlideViewName = "MainPanel";
        internal const string LeftPanelButtonName = "LeftPanelButton";
        internal const string RightPanelButtonName = "RightPanelButton";
        internal const string HeaderGridName = "HeaderGrid";

        private const int IndexLeftPanel = 0;
        private const int IndexCenterPanel = 1;
        private const int IndexRightPanel = 2;

        #region LeftContent (DependencyProperty)

        public object LeftContent
        {
            get { return (object)GetValue(LeftContentProperty); }
            set { SetValue(LeftContentProperty, value); }
        }
        public static readonly DependencyProperty LeftContentProperty =
            DependencyProperty.Register("LeftContent", typeof(object), typeof(SlideApplicationFrame),
              new PropertyMetadata(null));

        #endregion

        #region RightContent (DependencyProperty)

        public object RightContent
        {
            get { return (object)GetValue(RightContentProperty); }
            set { SetValue(RightContentProperty, value); }
        }
        public static readonly DependencyProperty RightContentProperty =
            DependencyProperty.Register("RightContent", typeof(object), typeof(SlideApplicationFrame),
              new PropertyMetadata(null));

        #endregion

        #region Title (DependencyProperty)

        /// <summary>
        /// App title
        /// </summary>
        public string Title
        {
            get { return (string)GetValue(TitleProperty); }
            set { SetValue(TitleProperty, value); }
        }
        public static readonly DependencyProperty TitleProperty =
            DependencyProperty.Register("Title", typeof(string), typeof(SlideApplicationFrame),
              new PropertyMetadata(null));

        #endregion

        #region IsHeaderVisible (DependencyProperty)

        public static readonly DependencyProperty IsHeaderVisibleProperty =
            DependencyProperty.Register("IsHeaderVisible", typeof(bool), typeof(SlideApplicationFrame), new PropertyMetadata(true, IsHeaderVisibleChanged));

        public bool IsHeaderVisible
        {
            get { return (bool)GetValue(IsHeaderVisibleProperty); }
            set { SetValue(IsHeaderVisibleProperty, value); }
        }

        private static void IsHeaderVisibleChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var slider = sender as SlideApplicationFrame;
            if (slider == null)
            {
                return;
            }

            if (slider._headerGrid == null)
            {
                return;
            }

            slider._headerGrid.Visibility = slider.IsHeaderVisible ? Visibility.Visible : Visibility.Collapsed;
        }

        #endregion

        #region IsSlideEnabled (DependencyProperty)

        /// <summary>
        /// If true, enables the slide interaction between panels, otherwise disables it
        /// </summary>
        public bool IsSlideEnabled
        {
            get { return (bool)GetValue(IsSlideEnabledProperty); }
            set { SetValue(IsSlideEnabledProperty, value); }
        }
        public static readonly DependencyProperty IsSlideEnabledProperty =
            DependencyProperty.Register("IsSlideEnabled", typeof(bool), typeof(SlideApplicationFrame),
            new PropertyMetadata(true, OnIsSlideEnabledChanged));

        private static void OnIsSlideEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ((SlideApplicationFrame)d).OnIsSlideEnabledChanged();
        }

        protected virtual void OnIsSlideEnabledChanged()
        {
            if (_mainPanel != null)
                _mainPanel.IsSlideEnabled = IsSlideEnabled;

            if (_leftButton != null)
                _leftButton.Visibility = IsSlideEnabled ? Visibility.Visible : Visibility.Collapsed;

            if (_rightButton != null)
                _rightButton.Visibility = IsSlideEnabled ? Visibility.Visible : Visibility.Collapsed;
        }

        #endregion

        #region HideAppBarWhenOffCentre (DependencyProperty)
        public static readonly DependencyProperty HideAppBarWhenOffCentreProperty = DependencyProperty.Register(
            "HideAppBarWhenOffCentre", typeof(bool), typeof(SlideApplicationFrame), new PropertyMetadata(default(bool)));

        public bool HideAppBarWhenOffCentre
        {
            get { return (bool)GetValue(HideAppBarWhenOffCentreProperty); }
            set { SetValue(HideAppBarWhenOffCentreProperty, value); }
        } 
        #endregion

        public static readonly DependencyProperty ContentVisibleProperty =
            DependencyProperty.Register("ContentVisible", typeof(ContentVisible), typeof(SlideApplicationFrame), new PropertyMetadata(default(ContentVisible)));

        public ContentVisible ContentVisible
        {
            get { return (ContentVisible)GetValue(ContentVisibleProperty); }
            set { SetValue(ContentVisibleProperty, value); }
        }

        private SlideView _mainPanel;
        private Button _leftButton;
        private Button _rightButton;
        private Grid _headerGrid;

        public SlideApplicationFrame()
        {
            DefaultStyleKey = typeof(SlideApplicationFrame);

            Navigating += SlideApplicationFrame_Navigating;
            BackKeyPress += SlideApplicationFrame_BackKeyPress;
        }

        void SlideApplicationFrame_Navigating(object sender, System.Windows.Navigation.NavigatingCancelEventArgs e)
        {
            // Every time we navigate, we animate to the center panel
            if (_mainPanel != null)
                _mainPanel.SelectedIndex = IndexCenterPanel;
        }

        void SlideApplicationFrame_BackKeyPress(object sender, System.ComponentModel.CancelEventArgs e)
        {
            // Pressing back displays the center panel
            if (ContentVisible != ContentVisible.Center)
            {
                e.Cancel = true;
                ShowCenterContent();
            }
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            _mainPanel = GetTemplateChild(SlideViewName) as SlideView;
            if (_mainPanel != null)
                _mainPanel.SelectionChanged += MainPanelOnSelectionChanged;

            _leftButton = GetTemplateChild(LeftPanelButtonName) as Button;
            if (_leftButton != null)
                _leftButton.Click += LeftPanelButton_Click;

            _rightButton = GetTemplateChild(RightPanelButtonName) as Button;
            if (_rightButton != null)
                _rightButton.Click += RightPanelButton_Click;

            _headerGrid = GetTemplateChild(HeaderGridName) as Grid;
            if (_headerGrid != null)
                _headerGrid.Visibility = IsHeaderVisible ? Visibility.Visible : Visibility.Collapsed;

            OnIsSlideEnabledChanged();
        }

        public void ShowCenterContent()
        {
            if (_mainPanel != null)
            {
                _mainPanel.SelectedIndex = 1;
            }
        }

        private void MainPanelOnSelectionChanged(object sender, EventArgs eventArgs)
        {
            if (_mainPanel == null) return;

            switch (_mainPanel.SelectedIndex)
            {
                case 0:
                    ContentVisible = ContentVisible.Left;
                    ShowHideApplicationBar(false);
                    break;
                case 1:
                    ContentVisible = ContentVisible.Center;
                    ShowHideApplicationBar(true);
                    break;
                case 2:
                    ContentVisible = ContentVisible.Right;
                    ShowHideApplicationBar(false);
                    break;
            }
        }

        private void ShowHideApplicationBar(bool isCentre)
        {
            if (!HideAppBarWhenOffCentre) return;

            var page = Content as PhoneApplicationPage;
            if (page != null && page.ApplicationBar != null)
            {
                page.ApplicationBar.IsVisible = isCentre;
            }
        }

        void RightPanelButton_Click(object sender, RoutedEventArgs e)
        {
            if (_mainPanel.SelectedIndex != IndexRightPanel)
                _mainPanel.SelectedIndex = IndexRightPanel;
            else
                _mainPanel.SelectedIndex = IndexCenterPanel;
        }

        void LeftPanelButton_Click(object sender, RoutedEventArgs e)
        {
            if (_mainPanel.SelectedIndex != IndexLeftPanel)
                _mainPanel.SelectedIndex = IndexLeftPanel;
            else
                _mainPanel.SelectedIndex = IndexCenterPanel;
        }
    }
}