mundodelphi

Controling the number of application instances, controlar el numero de instancias de nuestra aplicacion en delphi

Prevenir que nuestra aplicación en delphi se execute dos instancias a la vez, el truco está separado por dos partes

creamos una unidad nueva i le llamamos CheckPrevious.pas

unit CheckPrevious;

interface
uses Windows, SysUtils;

function RestoreIfRunning(const AppHandle : THandle; MaxInstances : integer = 1) : boolean;

implementation

type
PInstanceInfo = ^TInstanceInfo;
TInstanceInfo = packed record
PreviousHandle : THandle;
RunCounter : integer;
end;

var
MappingHandle: THandle;
InstanceInfo: PInstanceInfo;
MappingName : string;

RemoveMe : boolean = True;

function RestoreIfRunning(const AppHandle : THandle; MaxInstances : integer = 1) : boolean;
begin
Result := True;
MappingName := StringReplace(ParamStr(0), '\',  '', [rfReplaceAll, rfIgnoreCase]);
MappingHandle := CreateFileMapping($FFFFFFFF, nil, PAGE_READWRITE,  0, SizeOf(TInstanceInfo), PChar(MappingName));

if MappingHandle = 0 then
RaiseLastOSError
else
begin
if GetLastError <> ERROR_ALREADY_EXISTS then
begin
InstanceInfo := MapViewOfFile(MappingHandle, FILE_MAP_ALL_ACCESS, 0, 0, SizeOf(TInstanceInfo));
InstanceInfo^.PreviousHandle := AppHandle;
InstanceInfo^.RunCounter := 1;

Result := False;
end
else //already runing
begin
MappingHandle := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, PChar(MappingName));
if MappingHandle <> 0 then
begin
InstanceInfo := MapViewOfFile(MappingHandle, FILE_MAP_ALL_ACCESS, 0, 0, SizeOf(TInstanceInfo));
if InstanceInfo^.RunCounter >= MaxInstances then
begin
RemoveMe := False;
if IsIconic(InstanceInfo^.PreviousHandle) then
ShowWindow(InstanceInfo^.PreviousHandle, SW_RESTORE);
SetForegroundWindow(InstanceInfo^.PreviousHandle);
end
else
begin
InstanceInfo^.PreviousHandle := AppHandle;
InstanceInfo^.RunCounter := 1 + InstanceInfo^.RunCounter;

Result := False;
end
end;
end;
end;
end; (*RestoreIfRunning*)

initialization
//nothing special here
//we need this section because we have the
//finalization section

finalization
//remove this instance
if RemoveMe then
begin
MappingHandle := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, PChar(MappingName));
if MappingHandle <> 0 then
begin
InstanceInfo := MapViewOfFile(MappingHandle, FILE_MAP_ALL_ACCESS, 0, 0, SizeOf(TInstanceInfo));
InstanceInfo^.RunCounter := -1 + InstanceInfo^.RunCounter;
end
else
RaiseLastOSError;
end;

if Assigned(InstanceInfo) then UnmapViewOfFile(InstanceInfo);
if MappingHandle <> 0 then CloseHandle(MappingHandle);

end. (*unit CheckPrevious*)

{
********************************************
Zarko Gajic
About.com Guide to Delphi Programming

http://delphi.about.com

email: delphi.guide@about.com
free newsletter: http://delphi.about.com/library/blnewsletter.htm
forum: http://forums.about.com/ab-delphi/start/
********************************************
}

y justo en la inicialización de la aplicación

program Project1;

uses
Forms,  Unit1 in 'Unit1.pas' {Form1},  CheckPrevious in 'CheckPrevious.pas';

{$R *.res}

begin
//permetir solo una instancia
if not CheckPrevious.RestoreIfRunning(Application.Handle, 1) then
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;
end;
end.

Fuente: delphiabout.com
Descarga: codigo fuente