桌面窗口集合更改时调用异步委托？

Question

我有一个 C# 程序来轮询对 EnumDesktopWindows 集合的更改。如果用户关闭或打开一个窗口，轮询例程会检测到这一点并将可用窗口的更新列表发送到另一个 .Net windows 窗体项目。但是，我不喜欢轮询方法。我希望对 EnumDesktopWindows 的任何更改都会触发一个事件，以便异步完成对更改的响应。

我能想到的最好的就是你在下面看到的。我尝试了 Scott C. 从控制台窗口执行的建议，但没有奏效。

目前，您在下面看到的内容在 Windows 窗体加载时捕获 CreateWnd=3（这是一个 Windows 窗体应用程序）。但是它不会全局捕获：它仅从当前运行的可执行文件中捕获窗口事件。如果有人有鹰眼并且可以发现如何在全球范围内捕获此代码，我将奖励答案。

尝试一下；首先创建一个Windows Forms应用项目，在Form1.cs中添加如下代码（需要在名为lstLog的Form中添加一个ListBox才能正确编译）

using System;
using System.Windows.Forms;

namespace Utilities
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            var gwh = new GlobalWindowHook();
            gwh.WindowCreated += onWindowCreated;
        }

        private void onWindowCreated()
        {
            lstLog.Items.Add("window creation event detected.");
        }
    }
}

在同一个项目中创建一个名为 GlobalWindowHook.cs 的类文件并复制粘贴以下内容：

using System;
using System.Runtime.InteropServices;

namespace Utilities
{
    internal class GlobalWindowHook
    {
        private delegate IntPtr HookProc(int code, IntPtr wParam, IntPtr lParam);

        [DllImport("user32.dll")]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

        public enum HookType
        {
            WH_JOURNALRECORD = 0,
            WH_JOURNALPLAYBACK = 1,
            WH_KEYBOARD = 2,
            WH_GETMESSAGE = 3,
            WH_CALLWNDPROC = 4,
            WH_CBT = 5,
            WH_SYSMSGFILTER = 6,
            WH_MOUSE = 7,
            WH_HARDWARE = 8,
            WH_DEBUG = 9,
            WH_SHELL = 10,
            WH_FOREGROUNDIDLE = 11,
            WH_CALLWNDPROCRET = 12,
            WH_KEYBOARD_LL = 13,
            WH_MOUSE_LL = 14
        }

        public enum HCBT
        {
            MoveSize = 0,
            MinMax = 1,
            QueueSync = 2,
            CreateWnd = 3,
            DestroyWnd = 4,
            Activate = 5,
            ClickSkipped = 6,
            KeySkipped = 7,
            SysCommand = 8,
            SetFocus = 9
        }

        private IntPtr hhook = IntPtr.Zero;

        public GlobalWindowHook()
        {
            hook();
        }


        ~GlobalWindowHook()
        {
            unhook();
        }


        public void hook()
        {
            IntPtr hInstance = LoadLibrary("User32");

            hhook = SetWindowsHookEx(HookType.WH_CBT, hookProc, hInstance, 0);
        }

        public void unhook()
        {
            UnhookWindowsHookEx(hhook);
        }

        public IntPtr hookProc(int code, IntPtr wParam, IntPtr lParam)
        {
            if (code != (int) HCBT.CreateWnd && code != (int) HCBT.DestroyWnd)
                return CallNextHookEx(IntPtr.Zero, code, wParam, lParam);

            //Do whatever with the created or destroyed window.

            return CallNextHookEx(IntPtr.Zero, code, wParam, lParam);
        }


        [DllImport("user32.dll")]
        private static extern IntPtr SetWindowsHookEx(HookType code, HookProc func, IntPtr hInstance, int threadId);

        [DllImport("user32.dll")]
        private static extern bool UnhookWindowsHookEx(IntPtr hInstance);

        [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Auto)]
        private static extern IntPtr LoadLibrary(string fileName);
    }
}

执行上述步骤后，执行 windows 窗体项目。您应该会看到它检测到正在创建一个窗口，即您刚刚执行的那个。

Answer 1

如果您想推送通知而不是拉取通知，这并不太难。您需要做的是 P/Invoke SetWindowsHookEx 并注册 WH_CBT 事件。收到这些消息后，您可以使用HCBT_CREATEWND or HCBT_DESTROYWND 代码收听消息。它会在新窗口创建或销毁时通知您。

使用pinvoke.net定义的类型

class HookingClass
{
    private delegate IntPtr CBTProc(HCBT nCode, IntPtr wParam, IntPtr lParam);

    private readonly CBTProc _callbackDelegate;

    public HookingClass()
    {
         _callbackDelegate = CallbackFunction;
    }

    private IntPtr _hook;

    private void CreateHook()
    {
        using (Process process = Process.GetCurrentProcess())
        using (ProcessModule module = process.MainModule)
        {
            IntPtr hModule = GetModuleHandle(module.ModuleName);

            _hook = SetWindowsHookEx(HookType.WH_CBT, _callbackDelegate, hModule, 0);
            if(_hook == IntPtr.Zero)
                throw new Win32Exception(); //The default constructor automatically calls Marshal.GetLastError()
        }

    }

    private void Unhook()
    {
        var success = UnhookWindowsHookEx(_hook);
        if(!success)
            throw new Win32Exception();
    }

     private IntPtr CallbackFunction(HCBT code, IntPtr wParam, IntPtr lParam)
     {
         if (code != HCBT.CreateWnd && code != HCBT.DestroyWnd) 
         {         
             return CallNextHookEx(IntPtr.Zero, code, wParam, lParam);
         }

         //Do whatever with the created or destroyed window.

         return CallNextHookEx(IntPtr.Zero, (int)code, wParam, lParam);
     }
}