delphi - 将字符串传递给已运行的应用程序实例

Question

我有一个应用程序，可以检测是否有该应用程序的另一个实例正在运行，如果找到则退出。这部分似乎工作可靠。我的应用程序采用一个命令行参数，我想将其传递给已经运行的实例。到目前为止我有以下代码:

项目1.dpr

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.

AppInstanceControl.pas

{ 基于 Zarko Gajic 的代码 http://delphi.about.com/library/code/ncaa100703a.htm }

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.

在主表单单元中:

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;

我很确定问题是我正在尝试将消息发送到正在运行的应用程序实例的句柄，但尝试在主窗体上处理消息。我想我这里有两个选择:

A) 从应用程序的句柄中以某种方式获取其主窗体的句柄并向那里发送消息。

B) 在应用程序而不是主表单级别处理消息接收。

我也不知道该怎么做。有更好的方法吗？

谢谢。

Answer 1

如果使用 WM_COPYDATA，则无需创建文件映射。这就是 WM_COPYDATA 的全部意义 - 它为您完成所有这些工作。

发送字符串

procedure IPCSendMessage(target: HWND;  const message: string);
var
  cds: TCopyDataStruct;
begin
  cds.dwData := 0;
  cds.cbData := Length(message) * SizeOf(Char);
  cds.lpData := Pointer(@message[1]);

  SendMessage(target, WM_COPYDATA, 0, LPARAM(@cds));
end;

接收字符串

procedure TForm1.WMCopyData(var msg: TWMCopyData);
var
  message: string;
begin
  SetLength(message, msg.CopyDataStruct.cbData div SizeOf(Char));
  Move(msg.CopyDataStruct.lpData^, message[1], msg.CopyDataStruct.cbData);

  // do something with the message e.g.
  Edit1.Text := message;
end;

根据需要进行修改以发送其他数据。