向 Windows 进程（不是其主窗口）发送消息

Question

我有一个应用程序，它在随后启动时检测是否有同名的进程已经在运行，如果是，则激活正在运行的应用程序的窗口，然后退出。

问题是主窗口可能被隐藏（只有一个通知区域图标可见），因此我没有窗口句柄。

在启动时，前一个实例的MainWindowHandle 属性为0，所以我无法发送ShowWindow 或PostMessage。

有什么方法可以发送一条可以被正在运行的应用程序拦截的消息，从而允许它显示其主窗口？

应用程序是用 C# 编写的，下面是我用来实现此目的的代码。

[STAThread]
static void Main()
{
    bool createdNew = true;
    using (Mutex mutex = new Mutex(true, "MyMutexName", out createdNew))
    {
        if (createdNew)
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        }
        else
        {
            Process current = Process.GetCurrentProcess();
            foreach (Process process in Process.GetProcessesByName(current.ProcessName))
            {
                if (process.Id != current.Id)
                {
                    Interop.WINDOWINFO pwi = new Interop.WINDOWINFO();
                    IntPtr handle = process.MainWindowHandle;
                    var isVisible = Interop.GetWindowInfo(handle, ref pwi);
                    if (!isVisible)
                    {
                        MessageBox.Show(Constants.APP_NAME + " is already running, check the notification area (near the clock).", 
                                        Constants.APP_NAME, MessageBoxButtons.OK, MessageBoxIcon.Information);//temporary message, until I find the solution
                        //Interop.ShowWindow(handle, Interop.WindowShowStyle.ShowNormal);
                        //Interop.PostMessage(handle, Interop.WM_CUSTOM_ACTIVATEAPP, IntPtr.Zero, IntPtr.Zero);
                    }
                    else
                        Interop.SetForegroundWindow(handle);//this works when the window is visible
                        break;
                    }
                }
            }
        }
    }
}

Answer 1

我是这样做的：

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
public partial class MainForm : Form
{
    #region Dll Imports
    private const int HWND_BROADCAST = 0xFFFF;

    private static readonly int WM_MY_MSG = RegisterWindowMessage( "WM_MY_MSG" );

    [DllImport( "user32" )]
    private static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam);

    [DllImport( "user32" )]
    private static extern int RegisterWindowMessage(string message);
    #endregion Dll Imports
    static Mutex _single = new Mutex(true, "{4EABFF23-A35E-F0AB-3189-C81203BCAFF1}");
    [STAThread]
    static void Main()
    {
        // See if an instance is already running...
        if (_single.WaitOne(TimeSpan.Zero, true)) {
            // No...start up normally.
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            try {
                Application.Run(new MainForm());
            } catch (Exception ex) {
                // handle exception accordingly
            } finally {
                _single.ReleaseMutex();
            }
        } else {
            // Yes...Bring existing instance to top and activate it.
            PostMessage(
                (IntPtr) HWND_BROADCAST,
                WM_MY_MSG,
                new IntPtr(0xCDCD),
                new IntPtr(0xEFEF));
        }
    }

    protected override void WndProc(ref Message m)
    {
        if (m.Msg == WM_MY_MSG) {
            if ((m.WParam.ToInt32() == 0xCDCD) && (m.LParam.ToInt32() == 0xEFEF)) {
                if (WindowState == FormWindowState.Minimized) {
                    WindowState = FormWindowState.Normal;
                }
                // Bring window to front.
                bool temp = TopMost;
                TopMost = true;
                TopMost = temp;
                // Set focus to the window.
                Activate();
            }
        } else {
            base.WndProc(ref m);
        }
    }
}

我希望我的转录正确。我不得不省略很多其他的东西，但我想我得到了必要的东西。我所拥有的对我有用。如果您有问题，请告诉我，我会看看我错过了什么。

Answer 2

命名管道可以用于此。这可能是 .net 更容易接受的方法。您可以在主应用程序中定义一个服务，该服务接受来自调用应用程序的消息。这是服务的示例，在 vb 中。它调用主应用程序并向其传递一个字符串，在本例中为一个文件名。它也返回一个字符串，但这里可以使用任何参数。

Public Class PicLoadService : Implements IMainAppPicLoad

Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
' do some stuff here.
LoadPic = "return string"
End Function

End Class

调用应用程序中的设置更复杂一些。调用和主应用程序可以是同一个应用程序。

Imports System.Diagnostics
Imports System.ServiceModel
Imports System.IO
Imports vb = Microsoft.VisualBasic

Module MainAppLoader

Sub Main()

Dim epAddress As EndpointAddress
Dim Client As picClient
Dim s As String
Dim loadFile As String
Dim procs() As Process
Dim processName As String = "MainApp"

loadFile = "" ' filename to load

procs = Process.GetProcessesByName(processName)

If UBound(procs) >= 0 Then
  epAddress = New EndpointAddress("net.pipe://localhost/MainAppPicLoad")
  Client = New picClient(New NetNamedPipeBinding, epAddress)
  s = Client.LoadPic(loadFile)
End If

End Sub

<System.Diagnostics.DebuggerStepThroughAttribute(), _
 System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")> _
Partial Public Class picClient
    Inherits System.ServiceModel.ClientBase(Of IMainAppPicLoad)
    Implements IMainAppPicLoad

    Public Sub New(ByVal binding As System.ServiceModel.Channels.Binding, ByVal remoteAddress As System.ServiceModel.EndpointAddress)
        MyBase.New(binding, remoteAddress)
    End Sub

    Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
        Return MyBase.Channel.LoadPic(fName)
    End Function

End Class

' from here down was auto generated by svcutil.
' svcutil.exe /language:vb /out:generatedProxy.vb /config:app.config http://localhost:8000/MainAppPicLoad
' Some has been simplified after auto code generation.
<System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0"), _
 System.ServiceModel.ServiceContractAttribute(ConfigurationName:="IMainAppPicLoad")> _
Public Interface IMainAppPicLoad
  <System.ServiceModel.OperationContractAttribute(Action:="http://tempuri.org/IMainAppPicLoad/LoadPic", ReplyAction:="http://tempuri.org/IMainAppPicLoad/LoadPicResponse")> _
  Function LoadPic(ByVal fName As String) As String
End Interface

<System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")> _
Public Interface IMainAppPicLoadChannel
  Inherits IMainAppPicLoad, System.ServiceModel.IClientChannel
End Interface

<System.Diagnostics.DebuggerStepThroughAttribute(), _
System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")> _
Partial Public Class IMainAppPicLoadClient
  Inherits System.ServiceModel.ClientBase(Of IMainAppPicLoad)
  Implements IMainAppPicLoad

  Public Sub New(ByVal binding As System.ServiceModel.Channels.Binding, ByVal remoteAddress As System.ServiceModel.EndpointAddress)
    MyBase.New(binding, remoteAddress)
  End Sub

  Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
    Return MyBase.Channel.LoadPic(fName)
  End Function
End Class

End Module

<ServiceContract()> Public Interface IMainAppPicLoad
<OperationContract()> Function LoadPic(ByVal fName As String) As String
End Interface

Answer 3

对于其他想要实现这一点的人，我将使用 Matt Davis 的解决方案发布在我的实现下方。

在 Program.cs 中

static class Program
{
    #region Dll Imports
    public const int HWND_BROADCAST = 0xFFFF;

    [DllImport("user32.dll")]
    public static extern bool SetForegroundWindow(IntPtr hWnd);

    [DllImport("user32")]
    public static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam);

    [DllImport("user32")]
    public static extern int RegisterWindowMessage(string message);
    #endregion Dll Imports

    public static readonly int WM_ACTIVATEAPP = RegisterWindowMessage("WM_ACTIVATEAPP");

    [STAThread]
    static void Main()
    {
        bool createdNew = true;
        //by creating a mutex, the next application instance will detect it
        //and the code will flow through the "else" branch 
        using (Mutex mutex = new Mutex(true, "MyMutexName", out createdNew))//make sure it's an unique identifier (a GUID would be better)
        {
            if (createdNew)
            {
                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);
                Application.Run(new MainForm());
            }
            else
            {
                //we tried to create a mutex, but there's already one (createdNew = false - another app created it before)
                //so there's another instance of this application running
                Process currentProcess = Process.GetCurrentProcess();

                //get the process that has the same name as the current one but a different ID
                foreach (Process process in Process.GetProcessesByName(currentProcess.ProcessName))
                {
                    if (process.Id != currentProcess.Id)
                    {
                        IntPtr handle = process.MainWindowHandle;

                        //if the handle is non-zero then the main window is visible (but maybe somewhere in the background, that's the reason the user started a new instance)
                        //so just bring the window to front
                        if (handle != IntPtr.Zero)
                            SetForegroundWindow(handle);
                        else
                            //tough luck, can't activate the window, it's not visible and we can't get its handle
                            //so instead notify the process that it has to show it's window
                            PostMessage((IntPtr)HWND_BROADCAST, WM_ACTIVATEAPP, IntPtr.Zero, IntPtr.Zero);//this message will be sent to MainForm

                        break;
                    }
                }
            }
        }
    }
}

在 MainForm.cs 中

protected override void WndProc(ref Message m)
{
    base.WndProc(ref m);
            //someone (another process) said that we should show the window (WM_ACTIVATEAPP)
    if (m.Msg == Program.WM_ACTIVATEAPP)
        this.Show();
}