خوب معلومه که باید از نوشتن در حافظه استفاده کرد!!!
برای انجام اینکار از Mutex ها استفاده میکنیم:
کد برای استفاده در سورس پروژه:{The code for ONEINSTANCE.dpr}
program ONEINSTANCE;
uses
Windows,
Forms,
Unit1 in 'Unit1.pas' {Form1};
{$R *.RES}
begin
{Attempt to create a named mutex}
CreateMutex(nil, false, 'MyApp');
{if it failed then there is another INSTANCE}
if GetLastError = ERROR_ALREADY_EXISTS then begin
{Send all windows our custom message - only our other}
{INSTANCE will recognise it, and restore itself}
SendMessage(HWND_BROADCAST,
RegisterWindowMessage('MyApp'),
0,
0);
{Lets quit}
Halt(0);
end;
Application.Initialize;
{Tell Delphi to un-hide it's hidden application window}
{This allows our INSTANCE to have a icon on the task bar}
Application.ShowMainForm := true;
ShowWindow(Application.Handle, SW_RESTORE);
Application.CreateForm(TForm1, Form1);
Application.Run;
end.
کد برای استفاده در Unit1.pas:unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls,
Forms, Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
var
OldWindowProc : Pointer; {Variable for the old windows proc}
MyMsg : DWord; {custom systemwide message}
function NewWindowProc(WindowHandle : hWnd;
TheMessage : LongInt;
ParamW : LongInt;
ParamL : LongInt) : LongInt stdcall;
begin
if TheMessage = MyMsg then begin
{Tell the application to restore, let it restore the form}
SendMessage(Application.handle, WM_SYSCOMMAND, SC_RESTORE, 0);
SetForegroundWindow(Application.Handle);
{We handled the message - we are dONE}
Result := 0;
exit;
end;
{Call the original winproc}
Result := CallWindowProc(OldWindowProc,
WindowHandle,
TheMessage,
ParamW,
ParamL);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
{Register a custom windows message}
MyMsg := RegisterWindowMessage('MyApp');
{Set form1's windows proc to ours and remember the old window proc}
OldWindowProc := Pointer(SetWindowLong(Form1.Handle,
GWL_WNDPROC,
LongInt(@NewWindowProc)));
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
{Set form1's window proc back to it's original procedure}
SetWindowLong(Form1.Handle,
GWL_WNDPROC,
LongInt(OldWindowProc));
end;
begin
{Tell Delphi to hide it's hidden application window for now to avoid}
{a "flash" on the taskbar if we halt due to another INSTANCE}
ShowWindow(Application.Handle, SW_HIDE);
end.
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