[Silverlight入门系列]实现局部元素全屏(Element部分全屏)

本文不讨论Silverlight全屏模式的实现，有关实现这个，可以参考TerryLee的这篇文章，核心代码就是这行：

Application.Current.Host.Content.IsFullScreen = !Application.Current.Host.Content.IsFullScreen;

本文要讨论的是Silverlight的局部元素全屏，即Element部分全屏。我们在做Silverlight项目中有时候客户有这种需求：希望放大界面的局部，比如一个列表面板啥的，而不是整个界面全屏。如下图：

实现部分全屏

实现起来也是比较简单，主要思路是用Popup实现弹出全屏，把需要全屏的元素放到容器里并设置为屏幕大小，然后整体实现全屏；当用户退出全屏的时候需要把元素恢复回原位置。好，我们写一个ElementsFullScreenProvider类，实现一个UIElement的扩展方法即可。

主要实现类：ElementsFullScreenProvider

#region "Using Namespace"

using System;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Controls.Primitives;

#endregion

namespace ElementFullScreen

{

    /// <summary>

    /// Make partial UI elements full screen

    /// Provider features:

    ///    make UI element full screen

    ///    exit full screen and restore UI element

    ///    support UIElement.ToggleElementFullScreen -- extension methods

    /// </summary>

    public static class ElementsFullScreenProvider

    {

        #region Members

        static readonly Popup PopupContainer;

        static readonly Panel PopupContentContainer;

        static ElementController _lastElementController; 

        #endregion

        #region ElementController

        class ElementController

        {

            double _height = double.NaN;

            double _width = double.NaN;

            int _lastPanelPosition;

            bool _lastPopupIsOpen;

            readonly DependencyObject _parent;

            Thickness? _margin;

            public UIElement Element { get; private set; }

            public ElementController(UIElement element)

            {

                Element = element;

                var elem = element as FrameworkElement;

                if (elem != null && elem.Parent != null)

                {

                    _parent = elem.Parent;

                }

            }

            public void BringElementToFullScreen()

            {

                TryAction<frameworkelement>(Element, f =>

                {

                    _height = f.Height;

                    _width = f.Width;

                    f.Height = double.NaN;

                    f.Width = double.NaN;

                });

                TryAction<control>(Element, f =>

                {

                    _margin = f.Margin;

                    f.Margin = new Thickness(0);

                });

                if (_parent != null)

                {

                    if (!TryAction<panel>(_parent, p => { _lastPanelPosition = p.Children.IndexOf(Element); p.Children.RemoveAt(_lastPanelPosition); }))

                        if (!TryAction<contentcontrol>(_parent, c => c.Content = null))

                            if (!TryAction<usercontrol>(_parent, u => u.Content = null))

                                TryAction<popup>(_parent, p => { _lastPopupIsOpen = p.IsOpen; p.Child = null; });

                }

            }

            public void ReturnElementFromFullScreen()

            {

                TryAction<frameworkelement>(Element, f =>

                {

                    f.Height = _height;

                    f.Width = _width;

                });

                TryAction<control>(Element, f =>

                {

                    if (_margin.HasValue)

                    {

                        f.Margin = _margin.Value;

                    }

                });

                if (_parent != null)

                {

                    if (!TryAction<panel>(_parent, p => p.Children.Insert(_lastPanelPosition, Element)))

                        if (!TryAction<contentcontrol>(_parent, c => c.Content = Element))

                            if (!TryAction<usercontrol>(_parent, u => u.Content = Element))

                                TryAction<popup>(_parent, p => { p.Child = Element; p.IsOpen = _lastPopupIsOpen; });

                }

            }

            static bool TryAction<t>(object o, Action<t> action)

                where T : class

            {

                T val = o as T;

                if (val != null)

                {

                    action(val);

                    return true;

                }

                return false;

            }

        }

        #endregion

        #region FullscreenElementID Attached Property

        static readonly DependencyProperty FullscreenElementIDProperty = DependencyProperty.RegisterAttached(

           "FullscreenElementID", typeof(Guid?), typeof(ElementsFullScreenProvider), new PropertyMetadata(null));

        static void SetFullscreenElementID(DependencyObject obj, Guid? value)

        {

            obj.SetValue(FullscreenElementIDProperty, value);

        }

        static Guid? GetFullscreenElementID(DependencyObject obj)

        {

            return (Guid?)obj.GetValue(FullscreenElementIDProperty);

        }

        #endregion

        #region Initialization

        /// <summary>

        /// Initializes the <see cref="ElementsFullScreenProvider"> class.

        /// </see></summary>

        static ElementsFullScreenProvider()

        {

            PopupContentContainer = new Grid();

            PopupContainer = new Popup

            {

                Child = PopupContentContainer

            };

            Application.Current.Host.Content.FullScreenChanged += delegate

            {

                if (_lastElementController == null) return;

                if (!Application.Current.Host.Content.IsFullScreen)

                {

                    ReturnElementFromFullScreen();

                }

                else

                {

                    UpdateContentSize();

                }

            };

        } 

        #endregion

        #region Public Methods

        public static void BringElementToFullScreen(this UIElement element)

        {

            if (_lastElementController == null)

            {

                _lastElementController = new ElementController(element);

                _lastElementController.BringElementToFullScreen();

                PopupContentContainer.Children.Add(element);

                PopupContainer.IsOpen = true;

            }

        }

        public static void ReturnElementFromFullScreen(this UIElement element)

        {

            ReturnElementFromFullScreen();

        }

        public static void ReturnElementFromFullScreen()

        {

            if (_lastElementController != null)

            {

                PopupContentContainer.Children.Clear();

                _lastElementController.ReturnElementFromFullScreen();

                PopupContainer.IsOpen = false;

                _lastElementController = null;

            }

        }

        public static void ToggleElementFullScreen(this UIElement element)

        {

            bool newValue = !Application.Current.Host.Content.IsFullScreen;

            bool toggle = false;

            if (newValue)

            {

                if (_lastElementController == null)

                {

                    element.BringElementToFullScreen();

                    toggle = true;

                }

            }

            else

            {

                if (_lastElementController != null && ReferenceEquals(element, _lastElementController.Element))

                {

                    element.ReturnElementFromFullScreen();

                    toggle = true;

                }

            }

            if (toggle)

            {

                ToggleFullScreen();

            }

        }

        public static void ToggleFullScreen()

        {

            Application.Current.Host.Content.IsFullScreen = !Application.Current.Host.Content.IsFullScreen;

        }

        #endregion

        #region Private Method

        private static void UpdateContentSize()

        {

            if (Application.Current != null && Application.Current.Host != null && Application.Current.Host.Content != null)

            {

                double height = Application.Current.Host.Content.ActualHeight;

                double width = Application.Current.Host.Content.ActualWidth;

                //if (Application.Current.Host.Settings.EnableAutoZoom)

                //{

                //    double zoomFactor = Application.Current.Host.Content.ZoomFactor;

                //    if (zoomFactor != 0.0)

                //    {

                //        height /= zoomFactor;

                //        width /= zoomFactor;

                //    }

                //}

                PopupContentContainer.Height = height;

                PopupContentContainer.Width = width;

            }

        } 

        #endregion

    }

}

调用的时候使用UIElement的扩展方法实现全屏：

 1: private void button1_Click(object sender, RoutedEventArgs e)

 2: {

 3:  SilverArea/*你希望全屏的元素*/.ToggleElementFullScreen();//调用UIElement的扩展方法

 4:  }

本文源码下载请点击此处。主要就一个类ElementsFullScreenProvider.cs，用起来就一个函数ToggleElementFullScreen()，简单之极。

说明：本文出处：http://www.cnblogs.com/Mainz/archive/2011/08/19/2145933.html