Voici deux composants
TCmdEvent pour exécuter une seule instance de l'application.
le property Enabeled a false les parametres pour controler le déclenchement de l'événement OnQuery "Enabeled a false" les messages WM_COPYDATA reçus sont enregistre sur une liste interne pour déclencher cet événement Enabled a true
l'événement OnData "Enabeled a true" se déclenche a chaque message WM_COPYDATA reçu
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  if not CheckAndSet('My_Window_Id') then Exit;
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
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procedure TForm1.CmdEvent1Query(Sender: TObject);
var
  i:integer;
begin
   for i:= 0 to CmdEvent1.Count-1 do
     Showmessage(CmdEvent1[i]);
end;
 
procedure TForm1.CmdEvent1Data(const S: String);
begin
   Showmessage(S);
end;
TDragFilespour gerer les fichier lacher sur une fiche

Code : Sélectionner tout - Visualiser dans une fenêtre à part
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unit PrevInstance;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls,AppEvnts;
 
type
  TCmdStrings=class
  private
    FHWND    :HWND;
    FList    :TStrings;
    FEnabled :boolean;
    FAutoCLR :boolean;
    FId      :string;
    FOnQuery :TNotifyEvent;
    FOnData  :TGetStrProc;
    function  HasList():boolean;
    function  Get_Item(Idx:integer):string;
    function  Get_Count():integer;
    procedure Set_Enabled(AValue:boolean);
    procedure Add(const AValue:string);
    procedure ActivateApp();
  protected
    FChanged :boolean;
    procedure WndMethod(var Msg: TMessage);virtual;
    procedure DoQuery();virtual;
    procedure SendData();virtual;
    property  List :TStrings read FList;
  public
    constructor Create();
    destructor Destroy(); override;
    function CheckAndSet(const AId:string):boolean;
    procedure Clear();
    property Handle:HWND read FHWND;
    property Items[idx:integer]:string read Get_Item; default;
    property Count:integer read Get_Count;
    property ID :string read  FId;
    property Enabled :boolean read FEnabled write Set_Enabled;
    property AutoClear:boolean read FAutoCLR write FAutoCLR;
    property OnQuery :TNotifyEvent read FOnQuery write FOnQuery;
    property OnData  :TGetStrProc read FOnData write FOnData;
  end;
  TCmdEvent=class(TComponent)
  private
    FDEvent : TCmdStrings;
    function Get_AutoCLR: boolean;
    procedure Set_AutoCLR(const Value: boolean);
    function Get_OnData: TGetStrProc;
    function Get_OnQuery: TNotifyEvent;
    procedure Set_OnData(const Value: TGetStrProc);
    procedure Set_OnQuery(const Value: TNotifyEvent);
    function Get_Enabled: boolean;
    procedure Set_Enabled(const Value: boolean);
    function Get_Count: integer;
    function Get_Id: string;
    function Get_HWND: HWND;
    function Get_Item(idx: integer): string;
  public
    constructor Create(AOwner:TComponent);override;
    destructor Destroy();override;
    procedure Clear();
    property Handle:HWND read Get_HWND;
    property Items[idx:integer]:string read Get_Item; default;
    property Count:integer read Get_Count;
    property ID :string read  Get_Id;
  published
    property Enabled:boolean read Get_Enabled write Set_Enabled;
    property AutoClear:boolean read Get_AutoCLR write Set_AutoCLR;
    property OnQuery :TNotifyEvent read Get_OnQuery write Set_OnQuery;
    property OnData  :TGetStrProc read Get_OnData write Set_OnData;
  end;
 
  TDragFiles=class(TComponent)
  private
    FHandle  :HWND;
    FEvent   :TApplicationEvents;
    FAcceptFiles: boolean;
    FOnDragFiles: TGetStrProc;
    procedure WndMethod(var Msg:TagMsg;var Handled: Boolean);
    procedure SetAcceptFiles(const Value: boolean);
  public
    constructor Create(AOwner:TComponent);override;
    destructor Destroy();override;
  published
    property AcceptFiles :boolean read FAcceptFiles write SetAcceptFiles;
    property OnDragFiles :TGetStrProc read FOnDragFiles write FOnDragFiles;
  end;
 
function CheckAndSet(const AId:string):boolean;
 
procedure Register;
 
 
implementation
uses ShellApi;
type
  PCmdParam =^TCmdParam;
  TCmdParam = string[255];
var
  OnlyOneInst:TCmdEvent;
  CmdQuery   :TCmdStrings;
 
procedure Register;
begin
  RegisterComponents('Exemples', [TCmdEvent,TDragFiles]);
end;
 
function CheckAndSet(const AId:string):boolean;
begin
   result:=CmdQuery.CheckAndSet(AId);
end;
{=========================================================================
+                        TCmdStrings                                     +
=========================================================================}
constructor TCmdStrings.Create;
begin
    FEnabled :=true;
    FAutoCLR :=true;
end;
 
destructor TCmdStrings.Destroy();
begin
   Classes.DeallocateHWnd(FHWND);
   if HasList() then
      FList.Free();
   inherited;
end;
 
function  TCmdStrings.HasList():boolean;
begin
    result:=Assigned(FList);
end;
 
function TCmdStrings.CheckAndSet(const AId:string):boolean;
begin
  result:=true;
  if IsValidIdent(AId)then
   begin
      FHWND:= FindWindow(nil,PChar(AId));
      if FHWND = 0  then
      begin
         FHWND := Classes.AllocateHWnd(WndMethod);
         SetWindowText(FHWND,PChar(AId)) ;
         FId:=AId;
      end
     else
      begin
        SendData();
        result:=false;
      end;
   end ;
end;
 
procedure TCmdStrings.Set_Enabled(AValue:boolean);
begin
   if AValue = FEnabled then Exit;
 
   FEnabled := AValue;
   if FEnabled and FChanged then
   try
     DoQuery();
   finally
    if AutoClear then
       Clear();
    FChanged:=False;
   end;
end;
 
procedure TCmdStrings.ActivateApp();
var
  H:TForm;
begin
  H:= Application.MainForm;
  if Assigned(H)then
  begin
    if not IsWindowVisible (H.Handle) then
       Application.Restore();
    SetForegroundWindow (H.Handle);
  end;
end;
 
procedure TCmdStrings.WndMethod(var Msg : TMessage);
var
 S:string;
begin
  with Msg do
  if Msg = WM_COPYDATA then
  begin
     S:=Trim(PCmdParam(TCopyDataStruct(Pointer(LParam)^).lpData)^);
     try
       if Enabled and Assigned(FOnData)then
       begin
          ActivateApp();
           FOnData(S);
       end
         else
           Add(S);
     except
     end;
     Result := 0
  end
   else
    Result := DefWindowProc(FHWnd, Msg,WParam, LParam);
end;
 
procedure TCmdStrings.SendData();
var
  DataHolder :TCmdParam;
  CDStruct   :TCopyDataStruct;
begin
  Zeromemory(@DataHolder,SizeOf(TCmdParam));
  DataHolder      :=string(CmdLine);
  CDStruct.cbData :=SizeOf(TCmdParam);
  CDStruct.lpData :=@DataHolder;
  SendMessage(FHWND, WM_COPYDATA,0,LongInt(@CDStruct));
end;
 
procedure TCmdStrings.Add(const AValue:string);
begin
    if not HasList() then
       FList:=TStringList.Create();
    FList.Add(AValue);
    FChanged:=true;
end;
 
function TCmdStrings.Get_Item(Idx:integer):string;
begin
   result:='';
   if HasList() then
     result:= FList[Idx];
end;
 
function TCmdStrings.Get_Count():integer;
begin
   result:= 0;
   if HasList() then
     result:= FList.Count;
end;
 
procedure TCmdStrings.Clear();
begin
   if HasList() then
      FList.Clear();
end;
 
procedure TCmdStrings.DoQuery();
begin
    ActivateApp();
    if Assigned(FOnQuery) then FOnQuery(Self);
end;
 
{=========================================================================
+                        TCmdEvent                                       +
=========================================================================}
constructor TCmdEvent.Create(AOwner: TComponent);
begin
  if OnlyOneInst <> nil then
   raise Exception.Create('CmdQuery est utiliser par un autre objet');
  inherited ;
  OnlyOneInst:= Self;
  FDEvent := CmdQuery;
end;
 
destructor TCmdEvent.Destroy;
begin
  if OnlyOneInst = Self then
     OnlyOneInst:=nil;
  inherited;
end;
 
function TCmdEvent.Get_AutoCLR: boolean;
begin
   result:=FDEvent.AutoClear;
end;
 
function TCmdEvent.Get_Count: integer;
begin
  result:=FDEvent.Count;
end;
 
function TCmdEvent.Get_Enabled: boolean;
begin
   result:=FDEvent.Enabled;
end;
 
function TCmdEvent.Get_Id: string;
begin
  result:= FDEvent.ID;
end;
 
function TCmdEvent.Get_HWND: HWND;
begin
  result:= FDEvent.Handle;
end;
 
function TCmdEvent.Get_Item(idx: integer): string;
begin
  result:= FDEvent[idx];
end;
 
function TCmdEvent.Get_OnData: TGetStrProc;
begin
   result:=FDEvent.OnData;
end;
 
function TCmdEvent.Get_OnQuery: TNotifyEvent;
begin
   result:=FDEvent.OnQuery;
end;
 
procedure TCmdEvent.Set_AutoCLR(const Value: boolean);
begin
   FDEvent.AutoClear := Value;
end;
 
procedure TCmdEvent.Set_Enabled(const Value: boolean);
begin
  FDEvent.Enabled := Value;
end;
 
procedure TCmdEvent.Clear;
begin
   FDEvent.Clear();
end;
 
procedure TCmdEvent.Set_OnData(const Value: TGetStrProc);
begin
   FDEvent.OnData := Value;
end;
 
procedure TCmdEvent.Set_OnQuery(const Value: TNotifyEvent);
begin
   FDEvent.OnQuery := Value;
end;
 
{=========================================================================
+                        TDragFiles                                      +
=========================================================================}
constructor TDragFiles.Create(AOwner: TComponent);
begin
  inherited;
  if (TObject(AOwner) is TWinControl) then
  begin
    FEvent   :=TApplicationEvents.Create(Self);
    FEvent.OnMessage:= WndMethod;
    FHandle := TWinControl(AOwner).Handle;
    DragAcceptFiles(FHandle,true);
    FAcceptFiles:=true;
  end;
end;
 
destructor TDragFiles.Destroy();
begin
  AcceptFiles:=False;
  inherited;
end;
 
procedure TDragFiles.SetAcceptFiles(const Value: boolean);
begin
  if FHandle <> 0then
  begin
     FAcceptFiles:=Value;
     DragAcceptFiles(FHandle,FAcceptFiles);
  end;
end;
 
procedure TDragFiles.WndMethod(var Msg: TagMsg;var Handled: Boolean);
var
  N,I,Len:integer;
  S:string;
begin
  with Msg  do
  if (message=WM_DROPFILES) and (hwnd=FHandle) then
  begin
      N := DragQueryFile(LongWord(wParam), $FFFFFFFF, nil, 0);
      SetLength(S,MAX_PATH);
      for I:= 0 to N-1 do
      begin
        Len:=DragQueryFile(LongWord(wParam),I,PChar(S), MAX_PATH);
        if Assigned(FOnDragFiles) then
          FOnDragFiles(Copy(S,1,Len));
      end;
      Handled:=true;
   end;
end;
 
initialization
  CmdQuery:=TCmdStrings.Create();
 
 {System.InitProc := ???? }
finalization
  CmdQuery.Free();
end.