c# - 在媒体播放期间从 C# 中的 WPF 应用程序在 Windows 上启用屏幕保护程序

Question

我是 WPF 和 C# 的新手。我在一个简单的 WPF 应用程序中使用 MediaElement 来播放循环视频，使用 Storyboard。

现在在这个项目中我遇到了一个大问题。 MediaElement 中播放的视频阻止屏幕保护程序启动。但就我而言，我需要正常的 Windows 行为。 (自动屏保和自动注销等。)

即使我的 MediaElement 中正在播放视频，我怎样才能让正常的屏幕保护程序再次出现？

代码很简单:主窗口:

<Window x:Name="BrutusView" x:Class="BRUTUS_Panel_View.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:BRUTUS_Panel_View"
mc:Ignorable="d"
        Title="3nb BRUTUS Side Panel Player" Height="320" Width="256" HorizontalAlignment="Center" VerticalAlignment="Center" Left="0" Top="0" Deactivated="BrutusView_Deactivated" LostFocus="BrutusView_LostFocus" Loaded="BrutusView_Loaded" WindowStyle="ToolWindow" ResizeMode="CanResize" Icon="F:\Dokumente\Visual Studio 2015\Projects\BRUTUSConfig\BRUTUSConfig\3nb.ico" Topmost="True" ShowInTaskbar="False" ShowActivated="False" Visibility="Visible">
    <Grid>
        <MediaElement x:Name="myMediaElement" LoadedBehavior="Manual" HorizontalAlignment="Center"  VerticalAlignment="Center" IsMuted="True" Stretch="UniformToFill">
            <MediaElement.Triggers>
                <EventTrigger RoutedEvent="MediaElement.Loaded">
                    <EventTrigger.Actions>
                        <BeginStoryboard>
                            <Storyboard>
                                <MediaTimeline Source="C:\Animations\1.mp4" Storyboard.TargetName="myMediaElement" RepeatBehavior="Forever" />
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger.Actions>
                </EventTrigger>
            </MediaElement.Triggers>
        </MediaElement>
    </Grid>
</Window>

C#:

using System;
using System.Linq;
using System.Windows;
using System.Windows.Forms;
using System.Windows.Threading;

namespace BRUTUS_Panel_View
{

    public partial class MainWindow : Window
    {



        public MainWindow()
        {
            InitializeComponent();
        }

        private void BrutusView_Loaded(object sender, RoutedEventArgs e)
        {

        }

        private void BrutusView_Deactivated(object sender, EventArgs e)
        {
            BrutusView.Topmost = true;
        }

        private void BrutusView_LostFocus(object sender, RoutedEventArgs e)
        {
            BrutusView.Topmost = true;
        }

    }
}

Answer 1

Answer 包含两个解决方案:(i) 基于 UWP DisplayRequest 类，(ii) 基于更通用的自定义 ScreenSaverManager 类。

<强>1。 UWP DisplayRequest 类

Windows 提供直接方法来请求暂停屏幕保护程序并成功调用它保证屏幕保护程序不会因用户不活动而启动，即在媒体播放期间。可以使用再次启用屏幕保护程序的方法进行相反的操作。这两种方法在 Windows 10(UWP 运行时)中都可用，并且可以通过 Windows.System.Display.DisplayRequest 类访问。下面发布了如何在 UWP 应用程序之外(在 WPF 桌面应用程序中)使用它的示例。

在使用代码之前，有必要将以下引用添加到在 Visual Studio 中从模板创建的标准 WPF 应用程序:(i) Windows.winmd 来自目录:C:\Program文件 (x86)\Windows Kits\10\UnionMetadata 和 (ii) System.Runtime.WindowsRuntime.dll 来自目录:C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETCore\v4.5.1(或 v4.5)。

在播放过程中挂起或启用屏幕保护 Hook 开始和停止播放事件到相关方法。

using System;
using System.Windows;
using System.Windows.Controls;
using Windows.System.Display;

namespace SuspendScreenSaverWpf
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private DisplayRequest mDisplayRequest;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void SuspendButton_Click(object sender, RoutedEventArgs e)
        {
            Button b = sender as Button;
            if (b != null)
            {
                try
                {
                    if (mDisplayRequest == null)
                    {
                        // This call creates an instance of the displayRequest object
                        mDisplayRequest = new DisplayRequest();
                    }
                }
                catch (Exception ex)
                {
                    this.MessageBoard.Content = $"Error Creating Display Request: {ex.Message}";
                }

                if (mDisplayRequest != null)
                {
                    try
                    {
                        // This call activates a display-required request. If successful,
                        // the screen is guaranteed not to turn off automatically due to user inactivity.
                        mDisplayRequest.RequestActive();
                        this.MessageBoard.Content = $"Display request activated - ScreenSaver suspended";
                        this.EnableButton.IsEnabled = true;
                        this.SuspendButton.IsEnabled = false;
                    }
                    catch (Exception ex)
                    {
                        this.MessageBoard.Content = $"Error: {ex.Message}";
                    }
                }
            }
        }

        private void EnableButton_Click(object sender, RoutedEventArgs e)
        {
            Button b = sender as Button;
            if (b != null)
            {
                if (mDisplayRequest != null)
                {
                    try
                    {
                        // This call de-activates the display-required request. If successful, the screen
                        // might be turned off automatically due to a user inactivity, depending on the
                        // power policy settings of the system. The requestRelease method throws an exception
                        // if it is called before a successful requestActive call on this object.
                        mDisplayRequest.RequestRelease();
                        this.MessageBoard.Content = $"Display request released - ScreenSaver enabled.";
                        this.SuspendButton.IsEnabled = true;
                        this.EnableButton.IsEnabled = false;
                    }
                    catch (Exception ex)
                    {
                        this.MessageBoard.Content = $"Error: {ex.Message}";
                    }
                }
            }
        }
    }
}



<Window x:Class="SuspendScreenSaverWpf.MainWindow"
                    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                    xmlns:local="clr-namespace:SuspendScreenSaverWpf"
                    mc:Ignorable="d"
                    Title="MainWindow ScreenSaver management demo" Height="350" Width="525">
    <Grid>
        <Button x:Name="SuspendButton" IsEnabled="true" Content="Suspend ScreenSaver" HorizontalAlignment="Left" Margin="73,250,0,0" VerticalAlignment="Top" Width="150" Click="SuspendButton_Click"/>
        <Button x:Name="EnableButton" IsEnabled="False" Content="Enable ScreenSaver" HorizontalAlignment="Left" Margin="298,250,0,0" VerticalAlignment="Top" Width="150" Click="EnableButton_Click"/>
        <Label x:Name="MessageBoard" Content="Example project demonstrating how to disable ScreenSaver on Windows 10" HorizontalAlignment="Left" Height="78" Margin="73,39,0,0" VerticalAlignment="Top"  Width="375"/>

    </Grid>
</Window>

有关引用程序集以访问 Windows 10 UWP API 的另一说明可在 UwpDesktop NuGet package 的网页上找到. UwpDesktop 包本身似乎不会在至少最近两次 Windows 10 Creators 更新期间得到维护，但如果针对 10.0.14393 API，它仍然有用。

有关如何从 C/C++ 代码使用此方法的示例，请参阅 SDL Library 的 repo

<强>2。自定义 ScreenSaverManager 类

问题中具有挑战性的部分与 System.Windows.Controls.MediaElement 控件的未记录行为有关，该控件在媒体播放期间暂停屏幕保护程序。尽管从用户观看电影的角度来看，防止激活屏幕保护程序是一个很好的做法，但有些应用程序并不理想。出于安全原因或当播放媒体不是最重要的应用程序功能时强制禁用屏幕保护程序或工作站锁定不是一个好的做法。 Microsoft 应该提供可用于控制此功能的公共(public)属性 o 方法。

为了避免任何黑客攻击，我尝试仅使用 Win32 和 .NET/WPF 公共(public) API 来解决问题。最简单但最有效的解决方案是基于创建我们自己的 ScreenSaverManager，它复制操作系统功能并按需强制执行原始屏幕保护程序行为(自动屏幕保护程序和自动注销等 ).首先 ScreenSaverManager 读取当前 session 设置，并根据它们开始执行 session 策略绕过方法，这些方法用于阻止 MediaElement 的屏幕保护程序和 session 锁定。

using System;
using System.Timers;

namespace ManageScreenSaver.MediaElementWpf
{
    public class ScreenSaverManager
    {
        private static ScreenSaverManager _Manager;

        public static ScreenSaverManager Instance
        {
            get
            {
                if (_Manager != null)
                    return _Manager;

                _Manager = new ScreenSaverManager();
                return _Manager;
            }
        }

        private TimeSpan _ScreenSaverTimeout;
        private bool _IsScreenSaverSecure;
        private Timer _Timer;

        protected ScreenSaverManager()
        {
            _ScreenSaverTimeout = NativeMethods.ScreenSaverTimeout;
            _IsScreenSaverSecure = NativeMethods.IsScreenSaverSecure;
            _Timer = new Timer(_ScreenSaverTimeout.TotalMilliseconds/2);
            _Timer.AutoReset = false;
            _Timer.Elapsed += Timer_Elapsed;
            _Timer.Start();
        }

        private void Timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            var lastInput = NativeMethods.GetLastUserInputTimeInterval();
            MainWindow.Console.WriteLine($"Last user input interval: {lastInput}");
            if (lastInput >= _ScreenSaverTimeout)
            {
                StartScreenSaver();
            }
            else
            {
                _Timer.Interval = _ScreenSaverTimeout.Subtract(lastInput).TotalMilliseconds + 100;
                _Timer.Start();
            }
        }

        private void StartScreenSaver()
        {
            if (_IsScreenSaverSecure)
            {
                NativeMethods.LockWorkStationSession();
            }
            else
            {
                var result = NativeMethods.SendMessage((IntPtr) 0xffff, (uint) WindowMessage.WM_SYSCOMMAND, (uint) WmSysCommandParam.ScSCREENSAVE, 0);
            }
        }
    }
}

Interop 方法在单独的类 NativeMethods 中定义:

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

namespace ManageScreenSaver.MediaElementWpf
{
    public static class NativeMethods
    {
        public const uint SPI_GETSCREENSAVETIMEOUT = 0x000E;
        public const uint SPI_SETSCREENSAVETIMEOUT = 0x000F;
        public const uint SPI_GETSCREENSAVEACTIVE = 0x0010;
        public const uint SPI_SETSCREENSAVEACTIVE = 0x0011;
        public const uint SPI_SETSCREENSAVERRUNNING = 0x0061;
        public const uint SPI_SCREENSAVERRUNNING = SPI_SETSCREENSAVERRUNNING;
        public const uint SPI_GETSCREENSAVERRUNNING = 0x0072;
        public const uint SPI_GETSCREENSAVESECURE = 0x0076;
        public const uint SPI_SETSCREENSAVESECURE = 0x0077;

        public const uint SPIF_UPDATEINIFILE = 0x0001;
        public const uint SPIF_SENDWININICHANGE = 0x0002;
        public const uint SPIF_SENDCHANGE = SPIF_SENDWININICHANGE;

        [DllImport("user32.dll", CallingConvention = CallingConvention.Winapi, PreserveSig = true, SetLastError = true)]
        internal static unsafe extern bool SystemParametersInfo(uint  uiAction, uint  uiParam, void* pvParam, uint  fWinIni);

        [DllImport("user32.dll", CallingConvention = CallingConvention.Winapi, CharSet = CharSet.Unicode, PreserveSig = true, SetLastError = true)]
        internal static extern IntPtr DefWindowProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled);

        [DllImport("user32.dll", SetLastError = true)]
        static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        [DllImport("User32.dll", SetLastError = true)]
        internal static extern int SendMessage(IntPtr hWnd, uint msg, uint wParam, uint lParam);

        [DllImport("user32.dll", SetLastError = true)]
        internal static extern bool LockWorkStation();

        public static TimeSpan GetLastUserInputTimeInterval()
        {
            LASTINPUTINFO lastInputInfo = new LASTINPUTINFO();
            lastInputInfo.cbSize = (uint)Marshal.SizeOf(lastInputInfo);

            if (!GetLastInputInfo(ref lastInputInfo))
            {
                throw new Win32Exception(Marshal.GetLastWin32Error());
            }

            uint ticks = (uint)Environment.TickCount;
            var idleMiliseconds = ticks - lastInputInfo.dwTime;
            return idleMiliseconds > 0 ? TimeSpan.FromMilliseconds((double)idleMiliseconds) : default(TimeSpan);
        }


        public static void LockWorkStationSession()
        {
            if (!LockWorkStation())
            {
                throw new Win32Exception(Marshal.GetLastWin32Error());
            }
        }

        public static bool IsScreenSaverActive
        {
            get
            {
                bool enabled = false;
                unsafe
                {
                    var result = SystemParametersInfo(SPI_GETSCREENSAVEACTIVE, 0, &enabled, 0);
                    if (!result)
                    {
                        throw new Win32Exception(Marshal.GetLastWin32Error());
                    }
                    return enabled;
                }
            }
        }

        public static bool IsScreenSaverRunning
        {
            get
            {
                bool enabled = false;
                unsafe
                {
                    var result = SystemParametersInfo(SPI_GETSCREENSAVERRUNNING, 0, &enabled, 0);
                    if (!result)
                    {
                        throw new Win32Exception(Marshal.GetLastWin32Error());
                    }
                    return enabled;
                }
            }
        }

        public static bool IsScreenSaverSecure
        {
            get
            {
                bool enabled = false;
                unsafe
                {
                    var result = SystemParametersInfo(SPI_GETSCREENSAVESECURE, 0, &enabled, 0);
                    if (!result)
                    {
                        throw new Win32Exception(Marshal.GetLastWin32Error());
                    }
                    return enabled;
                }
            }
        }

        public static TimeSpan ScreenSaverTimeout
        {
            get
            {
                int timeout = 0;
                unsafe
                {
                    var result = SystemParametersInfo(SPI_GETSCREENSAVETIMEOUT, 0, &timeout, 0);
                    if (!result)
                    {
                        throw new Win32Exception(Marshal.GetLastWin32Error());
                    }
                    return TimeSpan.FromSeconds(timeout);
                }
            }
        }
    }

    [Flags]
    public enum WindowMessage : uint
    {
        WM_COMMAND = 0x0111,
        WM_SYSCOMMAND = 0x0112, 
    }

    public enum WmSysCommandParam : uint
    {
        ScSIZE        = 0xF000,
        ScMOVE        = 0xF010,
        ScMINIMIZE    = 0xF020,
        ScMAXIMIZE    = 0xF030,
        ScNEXTWINDOW  = 0xF040,
        ScPREVWINDOW  = 0xF050,
        ScCLOSE       = 0xF060,
        ScVSCROLL     = 0xF070,
        ScHSCROLL     = 0xF080,
        ScMOUSEMENU   = 0xF090,
        ScKEYMENU     = 0xF100,
        ScARRANGE     = 0xF110,
        ScRESTORE     = 0xF120,
        ScTASKLIST    = 0xF130,
        ScSCREENSAVE  = 0xF140,
        ScHOTKEY      = 0xF150,
        ScDEFAULT     = 0xF160,
        ScMONITORPOWER= 0xF170,
        ScCONTEXTHELP = 0xF180,
        ScSEPARATOR   = 0xF00F,
    }
 }   

最后有一个关于如何在 WPF 应用程序中使用 ScreenSaverManager 的例子:

<Window x:Class="ManageScreenSaver.MediaElementWpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ManageScreenSaver.MediaElementWpf"
        mc:Ignorable="d"
        Title="MainWindow" Height="570" Width="550" MinHeight="570" MinWidth="550" MaxHeight="570" MaxWidth="550">
    <Grid Margin="0,0,0,0">
        <MediaElement x:Name="myMediaElement" Width="530" Height="270" LoadedBehavior="Manual" HorizontalAlignment="Center"  VerticalAlignment="Center" IsMuted="True" Stretch="Fill" Margin="10,52,10,197" >
            <MediaElement.Triggers>
                <EventTrigger RoutedEvent="MediaElement.Loaded">
                    <EventTrigger.Actions>
                        <BeginStoryboard>
                            <Storyboard>
                                <MediaTimeline Source="..\..\BigBuckBunny_320x180.mp4" Storyboard.TargetName="myMediaElement" RepeatBehavior="Forever" />
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger.Actions>
                </EventTrigger>
            </MediaElement.Triggers>
        </MediaElement>
        <Button x:Name="SuspendButton" IsEnabled="true" Content="Suspend ScreenSaver" HorizontalAlignment="Left" Margin="74,489,0,0" VerticalAlignment="Top" Width="150" Click="SuspendButton_Click" RenderTransformOrigin="0.501,2.334"/>
        <Button x:Name="EnableButton" IsEnabled="true" Content="Enable ScreenSaver" HorizontalAlignment="Left" Margin="302,489,0,0" VerticalAlignment="Top" Width="150" Click="EnableButton_Click" RenderTransformOrigin="0.508,1.359"/>
        <Label x:Name="MessageBoard" Content="Example project demonstrating how to disable ScreenSaver on Windows 10" HorizontalAlignment="Left" Height="25" Margin="44,10,0,0" VerticalAlignment="Top"  Width="432"/>
        <TextBox x:Name="TextBox" Text="" HorizontalAlignment="Center" HorizontalContentAlignment="Left" Height="110" Margin="10,342,10,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="510"/>
    </Grid>
</Window>

using System;
using System.Timers;
using System.Windows;
using System.Windows.Controls;
using Windows.System.Display;

namespace ManageScreenSaver.MediaElementWpf
{
    public partial class MainWindow : Window
    {
        private DisplayRequest mDisplayRequest;
        internal static TextBoxWriter Console;
        private static ScreenSaverManager _ScreenSaverManager;

        public MainWindow()
        {
            InitializeComponent();
            Console = new TextBoxWriter(this.TextBox);
            _ScreenSaverManager = ScreenSaverManager.Instance;
            PrintSSaverStatus(" MainWindow.ctor");
        }

        private void PrintSSaverStatus(string apendedText = "")
        {
            Console.WriteLine(GetScreenSaverStatusMessage() + apendedText);
        }

        private void SuspendButton_Click(object sender, RoutedEventArgs e)
        {
            Button b = sender as Button;
            if (b != null)
            {
                EnsureDisplayRequest();

                if (mDisplayRequest != null)
                {
                    try
                    {
                        // This call activates a display-required request. If successful,
                        // the screen is guaranteed not to turn off automatically due to user inactivity.
                        mDisplayRequest.RequestActive();
                        this.MessageBoard.Content = $"Display request activated - ScreenSaver suspended";
                        this.EnableButton.IsEnabled = true;
                        this.SuspendButton.IsEnabled = false;
                    }
                    catch (Exception ex)
                    {
                        this.MessageBoard.Content = $"Error: {ex.Message}";
                    }

                    PrintSSaverStatus(" SuspendButton_Click");
                }
            }
        }

        private void EnsureDisplayRequest()
        {
            try
            {
                if (mDisplayRequest == null)
                {
                    // This call creates an instance of the displayRequest object
                    mDisplayRequest = new DisplayRequest();
                }
            }
            catch (Exception ex)
            {
                this.MessageBoard.Content = $"Error Creating Display Request: {ex.Message}";
            }
        }

        private void EnableButton_Click(object sender, RoutedEventArgs e)
        {
            Button b = sender as Button;
            if (b != null)
            {
                EnsureDisplayRequest();

                if (mDisplayRequest != null)
                {
                    try
                    {
                        // This call de-activates the display-required request. If successful, the screen
                        // might be turned off automatically due to a user inactivity, depending on the
                        // power policy settings of the system. The requestRelease method throws an exception
                        // if it is called before a successful requestActive call on this object.
                        mDisplayRequest.RequestRelease();
                        this.MessageBoard.Content = $"Display request released - ScreenSaver enabled.";
                        this.SuspendButton.IsEnabled = true;
                        this.EnableButton.IsEnabled = false;
                    }
                    catch (Exception ex)
                    {
                        this.MessageBoard.Content = $"Error: {ex.Message}";
                    }

                    PrintSSaverStatus(" EnableButton_Click");
                }
            }
        }

        private string GetScreenSaverStatusMessage()
        {
            string message = $"Screen Saver is: \"{{0}}\", \"{{1}}\", timeout: \"{{2}}\"  {DateTime.UtcNow}";
            message = String.Format(message,
                NativeMethods.IsScreenSaverActive ? "active" : "inactive",
                NativeMethods.IsScreenSaverSecure ? "secure" : "not secure",
                NativeMethods.ScreenSaverTimeout);
            return message;
        }
    }
}

仍然缺少 WPF 控制台的小实用程序:

using System;
using System.IO;
using System.Text;
using System.Windows.Controls;

namespace ManageScreenSaver.MediaElementWpf
{
    public class TextBoxWriter : TextWriter
    {

        private TextBox _TextBox;
        private string _NewLine = "\n";

        public TextBoxWriter(TextBox target)
        {
            if (target == null)
                throw new ArgumentNullException(nameof(target));

            _TextBox = target;
        }

        public override Encoding Encoding => new UTF8Encoding(false);

        public override string NewLine { get => _NewLine; set => _NewLine = value; }

        public override void Write(string value)
        {
            _TextBox.Dispatcher.InvokeAsync(
                () => _TextBox.AppendText(value)
                );
        }

        public override void WriteLine(string value)
        {
            _TextBox.Dispatcher.InvokeAsync(
                () => _TextBox.AppendText(value + NewLine)
                );
        }
    }
}

注意:这不是生产就绪代码。有必要实现错误处理、系统和监视器电源事件处理、登录和注销处理:工作站 session 开始和结束、 session 屏幕保护程序配置更改。

此方法有一些限制，在通过 RDP 连接到远程计算机时不起作用，但在通过控制台连接到 Hyper-V 中的 Windows VM 时有效。