问将字符串传递给已在运行的应用程序实例？

EN

program Project1;

uses
  ...
  AppInstanceControl in 'AppInstanceControl.pas';

  if not AppInstanceControl.RestoreIfRunning(Application.Handle) then
  begin
    Application.Initialize;
    Application.MainFormOnTaskbar := True;
    Application.CreateForm(TFormMain, FormMain);
    Application.Run;
  end;

end.

unit AppInstanceControl;

interface

uses
  Windows,
  SysUtils;

function RestoreIfRunning(const AAppHandle: THandle; const AMaxInstances: integer = 1): boolean;

implementation

uses
  Messages;

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

var
  UMappingHandle: THandle;
  UInstanceInfo: PInstanceInfo;
  UMappingName: string;

  URemoveMe: boolean = True;

function RestoreIfRunning(const AAppHandle: THandle; const AMaxInstances: integer = 1): boolean;
var
  LCopyDataStruct : TCopyDataStruct;
begin
  Result := True;

  UMappingName := StringReplace(
                   ParamStr(0),
                   '\',
                   '',
                   [rfReplaceAll, rfIgnoreCase]);

  UMappingHandle := CreateFileMapping($FFFFFFFF,
                                     nil,
                                     PAGE_READWRITE,
                                     0,
                                     SizeOf(TInstanceInfo),
                                     PChar(UMappingName));

  if UMappingHandle = 0 then
    RaiseLastOSError
  else
  begin
    if GetLastError <> ERROR_ALREADY_EXISTS then
    begin
      UInstanceInfo := MapViewOfFile(UMappingHandle,
                                    FILE_MAP_ALL_ACCESS,
                                    0,
                                    0,
                                    SizeOf(TInstanceInfo));

      UInstanceInfo^.PreviousHandle := AAppHandle;
      UInstanceInfo^.RunCounter := 1;

      Result := False;
    end
    else //already runing
    begin
      UMappingHandle := OpenFileMapping(
                                FILE_MAP_ALL_ACCESS, 
                                False, 
                                PChar(UMappingName));
      if UMappingHandle <> 0 then
      begin
        UInstanceInfo := MapViewOfFile(UMappingHandle,
                                      FILE_MAP_ALL_ACCESS,
                                      0,
                                      0,
                                      SizeOf(TInstanceInfo));

        if UInstanceInfo^.RunCounter >= AMaxInstances then
        begin
          URemoveMe := False;

          if IsIconic(UInstanceInfo^.PreviousHandle) then
            ShowWindow(UInstanceInfo^.PreviousHandle, SW_RESTORE);
          SetForegroundWindow(UInstanceInfo^.PreviousHandle);
        end
        else
        begin
          UInstanceInfo^.PreviousHandle := AAppHandle;
          UInstanceInfo^.RunCounter := 1 + UInstanceInfo^.RunCounter;

          Result := False;
        end
      end;
    end;
  end;
  if (Result) and (CommandLineParam <> '') then
  begin
    LCopyDataStruct.dwData := 0; //string
    LCopyDataStruct.cbData := 1 + Length(CommandLineParam);
    LCopyDataStruct.lpData := PChar(CommandLineParam);

    SendMessage(UInstanceInfo^.PreviousHandle, WM_COPYDATA, Integer(AAppHandle), Integer(@LCopyDataStruct));
  end;
end; (*RestoreIfRunning*)

initialization

finalization
  //remove this instance
  if URemoveMe then
  begin
    UMappingHandle := OpenFileMapping(
                        FILE_MAP_ALL_ACCESS, 
                        False, 
                        PChar(UMappingName));
    if UMappingHandle <> 0 then
    begin
      UInstanceInfo := MapViewOfFile(UMappingHandle,
                                  FILE_MAP_ALL_ACCESS,
                                  0,
                                  0,
                                  SizeOf(TInstanceInfo));

      UInstanceInfo^.RunCounter := -1 + UInstanceInfo^.RunCounter;
    end
    else
      RaiseLastOSError;
  end;

  if Assigned(UInstanceInfo) then UnmapViewOfFile(UInstanceInfo);
  if UMappingHandle <> 0 then CloseHandle(UMappingHandle);

end.

procedure TFormMain.WMCopyData(var Msg: TWMCopyData);
var
  LMsgString: string;
begin
  Assert(Msg.CopyDataStruct.dwData = 0);
  LMsgString := PChar(Msg.CopyDataStruct.lpData);

  //do stuff with the received string

end;