确保一个程序只运行一个实例(Delphi)

Delphi 代码：
//----------------------------------------------------------------------------

var
  hMutex:hwnd;
  ret:integer;
begin
  Application.Initialize;
  hmutex:=createMutex(nil,false,'MyAPP');
  ret:=getlasterror;
  if ret <>error_already_exists then
  begin
    Application.CreateForm(TMainFrm, MainFrm);
  Application.Run;
  end
  else
  begin
    Application.MessageBox('program已经运行,请不要运行两次','program不能运行',MB_搞定 or MB_ICONERROR);
  end;
  releasemutex(hmutex);
end.

//----------------------------------------------------------------------------

 
  二、通过查找系统原子表的方法来判断：  
  //---------------------------------------------------------------------------    
  #include   <vcl.h>  
  #pragma   hdrstop  
  USERES("Project1.res");  
  USEFORM("Unit1.cpp",   Form1);  
  //---------------------------------------------------------------------------  
  WINAPI   WinMain(HINSTANCE,   HINSTANCE,   LPSTR,   int)  
  {  
                                    const   char   *Atom   =   "SingleApp";  
                  try  
                  {  
                                    if   (GlobalFindAtom(Atom)   !=   0)//在系统原子表中找原子  
                                    {  
                                          ::MessageBox(NULL,"已经运行了一个实例!",Application->Title.c_str(),MB_OK|MB_SYSTEMMODAL);  
                                          return   0;  
                                    }  
                                    GlobalAddAtom(Atom);//增加原子  
                                    Application->Initialize();  
                                    Application->CreateForm(__classid(TForm1),   &Form1);  
                                    Application->Run();  
                  }  
                  catch   (Exception   &exception)  
                  {  
                                    Application->ShowException(&exception);  
                  }  
                  GlobalDeleteAtom(GlobalFindAtom(Atom));//删除原子  
                  return   0;  
  }  
  //---------------------------------------------------------------------------  
   
  三、通过FindWindow函数来判断：  
  //---------------------------------------------------------------------------  
   
  #include   <vcl.h>  
  #pragma   hdrstop  
  USERES("Project1.res");  
  USEFORM("Unit1.cpp",   Form1);  
  //---------------------------------------------------------------------------  
  WINAPI   WinMain(HINSTANCE,   HINSTANCE,   LPSTR,   int)  
  {  
                  try  
                  {  
                                    HWND   hdc   =   FindWindow("TForm1","Form1");  
                                    if   (NULL   !=   hdc)  
                                    {  
                                          ::MessageBox(NULL,"已经运行了一个实例!",Application->Title.c_str(),MB_OK|MB_SYSTEMMODAL);  
                                          return   0;  
                                    }  
                                    Application->Initialize();  
                                    Application->CreateForm(__classid(TForm1),   &Form1);  
                                    Application->Run();  
                  }  
                  catch   (Exception   &exception)  
                  {  
                                    Application->ShowException(&exception);  
                  }  
                  return   0;  
  }  
  //---------------------------------------------------------------------------