use a Mutex and check if it is occupied on startup Reference Controlling the number of application instances http://delphi.about.com/od/windowsshellapi/l/aa100703b.htm
PROGRAM xxx;USES Windows, ...VAR aHandle: HWND; aHandle:= CreateMutex(NIL, true, m_APP_NAME); IF GetLastError = Error_Already_Exists THEN BEGIN Application.MessageBox(m_APP_NAME + ' 已经启动!' + #13 + #13 + m_APP_NAME + ' is already running!', '', MB_ICONERROR); END ELSE BEGIN Application.Initialize; Application.Title:= 'xxx'; Application.CreateForm(TmenuForm, menuForm); Application.CreateForm(TAboutForm, AboutForm); Application.Run; END; CloseHandle(aHandle); END.
Reference
Controlling the number of application instances
http://delphi.about.com/od/windowsshellapi/l/aa100703b.htm
Windows,
...VAR
aHandle: HWND; aHandle:= CreateMutex(NIL, true, m_APP_NAME);
IF GetLastError = Error_Already_Exists THEN BEGIN
Application.MessageBox(m_APP_NAME + ' 已经启动!' + #13 + #13 + m_APP_NAME
+ ' is already running!', '', MB_ICONERROR);
END ELSE BEGIN
Application.Initialize;
Application.Title:= 'xxx';
Application.CreateForm(TmenuForm, menuForm);
Application.CreateForm(TAboutForm, AboutForm);
Application.Run;
END;
CloseHandle(aHandle);
END.
jiangsheng你好,http://delphi.about.com/od/windowsshellapi/l/aa100703b.htm中,我使用了那个sendMessage,就是重复启动时,向主Form发送一个消息,为什么收不到消息呢?是有特殊的要求吗?
代码中给出了一个MultInst.pas单元,工程引用此单元就能防止同时出现多个实例,
但实际应用中发现,如果应用程序并没有最小化,第二个实例不能把第一个实例提到最前.
下面是我改写的MultInst.pas单元,能解决这个小问题.
//==============================================================================
// Unit Name: MultInst
// Author : ysai
// Date : 2003-05-20
// Purpose : 解决应用程序多实例问题
// History :
//==============================================================================//==============================================================================
// 工作流程
// 程序运行先取代原有向所有消息处理过程,然后广播一个消息.
// 如果有其它实例运行,收到广播消息会回发消息给发送程序,并传回它自己的句柄
// 发送程序接收到此消息,激活收到消息的程序,然后关闭自己
//==============================================================================
unit MultInst;interfaceuses
Windows ,Messages, SysUtils, Classes, Forms;implementationconst
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);
//终止本实例
Application.Terminate;
end;
MI_GETHANDLE: //取得程序句柄
begin
PostMessage(HWND(lParam), iMessageID, MI_ACTIVEAPP,
Application.Handle);
end;
end;
end
else
Result := CallWindowProc(OldWProc, Handle, Msg, wParam, lParam);
end;procedure InitInstance;
begin
//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
begin
//建立互斥对象
MutHandle := CreateMutex(nil, False, STR_UNIQUE);
end
else begin
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;
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. //使用方法很简单,只要把此单元加入工程就可以了.