Delphi单元文件之－防止程序重复执行

//工程引用此单元就能防止同时出现多个实例

unit MultInst;

interface

uses Windows ,Messages, SysUtils, Classes, Forms;

implementation

const

  STR_UNIQUE    = '{2BE6D96E-827F-4BF9-B33E-8740412CDE96}';

  MI_ACTIVEAPP  = 1;  {激活应用程序}

  MI_GETHANDLE  = 2;  {取得句柄}

var

  iMessageID    : Integer;

  OldWProc      : TFNWndProc;

  MutHandle     : THandle;

  BSMRecipients : DWORD;

function NewWndProc(Handle: HWND; Msg: Integer; wParam, lParam: Longint): Longint; stdcall;

begin

  Result := 0;

  if Msg = iMessageID then

  begin

    case wParam of

      MI_ACTIVEAPP: {激活应用程序}

        if lParam<>0 then

        begin

          {收到消息的激活前一个实例}

          {为什么要在另一个程序中激活?}

          {因为在同一个进程中SetForegroundWindow并不能把窗体提到最前}

          if IsIconic(lParam) then

            OpenIcon(lParam)

          else

            SetForegroundWindow(lParam);

          Application.Terminate; {终止本实例}

        end;

      MI_GETHANDLE: {取得程序句柄}

          PostMessage(HWND(lParam), iMessageID, MI_ACTIVEAPP, Application.Handle);

    end;

  end

  else

    Result := CallWindowProc(OldWProc, Handle, Msg, wParam, lParam);

end;

procedure InitInstance;

  {取代应用程序的消息处理}

  OldWProc := TFNWndProc(SetWindowLong(Application.Handle, GWL_WNDPROC, Longint(@NewWndProc)));

  {打开互斥对象}

  MutHandle := OpenMutex(MUTEX_ALL_ACCESS, False, STR_UNIQUE);

  if MutHandle = 0 then

    {建立互斥对象}

    MutHandle := CreateMutex(nil, False, STR_UNIQUE);

    Application.ShowMainForm  :=  False;

    {已经有程序实例,广播消息取得实例句柄}

    BSMRecipients := BSM_APPLICATIONS;

    BroadCastSystemMessage(BSF_IGNORECURRENTTASK or BSF_POSTMESSAGE, @BSMRecipients, iMessageID, MI_GETHANDLE,Application.Handle);

  end;

initialization

  {注册消息}

  iMessageID  := RegisterWindowMessage(STR_UNIQUE);

  InitInstance;

finalization

  {还原消息处理过程}

  if OldWProc <> Nil then

    SetWindowLong(Application.Handle, GWL_WNDPROC, LongInt(OldWProc));

  {关闭互斥对象}

  if MutHandle <> 0 then

    CloseHandle(MutHandle);

end.