Mehrfachaufrufe verhindern...

[MrKnogge]

Bei der JediVCL ist ebenfalls eine Komponente vorhanden, desweiteren habe ich mal folgenden Code gefunden:

Delphi-Quellcode:

function BereitsAktiv: Boolean;
var 
  semName, 
  appClass: PChar; 
  hSem    : THandle; 
  hWndMe  : HWnd; 
  appTitle: Array[0..MAX_PATH] of Char; 
begin 
  // Init 
  Result := FALSE; 
  GetMem(semName,15); 
  GetMem(appClass,15); 
  StrPCopy(semName,'sema');
  StrPCopy(appClass,'TApplication'); 
  StrPCopy(appTitle,ExtractFileName(Application.Title)); 

  // Create a Semaphore in memory.  If this is the 
  // first instance, then hSem's value should be 0. 
  hSem := CreateSemaphore(nil,0,1,semName); 

  // Check to see if the semaphore exists 
  if (hSem <> 0) and (GetLastError() = 
                      ERROR_ALREADY_EXISTS) then 
    begin 
      CloseHandle(hSem); 

      // Get the current window's handle then change 
      // its title so we can look for the other instance 
      hWndMe := FindWindow(appClass,appTitle); 
      SetWindowText(hWndMe,'ZZZZZZZ'); 

      // Search for other instance of this window then bring 
      // it to the top of the Z-order stack.  We find it by 
      // matching the Application Class and 
      // Application Title. 
      hWndMe := FindWindow(appClass,appTitle); 
      if (hWndMe <> 0) then 
        begin 
          BringWindowToTop(hWndMe); 
          ShowWindow(hWndMe,SW_SHOWNORMAL);
          SetForeGroundWindow(hWndMe);
        end; 

      Result := TRUE; 
    end; 

  // Destroy PChars 
  FreeMem(semName,15); 
  FreeMem(appClass,15); 
end;

Initialization
if BereitsAktiv then
  Halt;