Question

我尝试在Windows中的两个应用程序之间交换数据。我使用了来自Zarko Gajic的示例。它使用Windows消息传递，该示例效果很好。有一个发送者和一个接收应用程序以及一些共享数据：全部为VCL编码。代码如下所示。

unit SenderMain;

{ How to send information (String, Image, Record) between two Delphi applications
http://delphi.about.com/od/windowsshellapi/a/wm_copydata.htm

Learn how to send the WM_CopyData message between two Delphi
applications to exchange information and make two applications
communicate. The accompanying source code demonstrates how to
send a string, record (complex data type) and even graphics
to another application.

~Zarko Gajic
About Delphi Programming
http://delphi.about.com
}
interface

uses
   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
   Dialogs, StdCtrls, ExtCtrls, TlHelp32,
   shared_data;

type
  TSenderMainForm = class(TForm)
    Button_Send_Data: TButton;
    Log: TListBox;

    procedure Button_Send_DataClick   (Sender: TObject);

   protected
      procedure Loaded; override;
      procedure SendString (send_string: aString);
   end; // Class: TSenderMainForm //

var
   SenderMainForm: TSenderMainForm;

implementation

{$R *.dfm}

{**************** NextWindow ****************}
function NextWindow (wnd: Thandle; list: Tstringlist):boolean; stdcall;
{This is the callback function which is called by EnumWindows procedure
 for each top-level window.  Return "true" to keep retrieving, return
 "false" to stop EnumWindows  from calling}
var
   title: array [0..255] of char;
   receiverHandle: HWND;//THandle;
   win_name: PChar;
   s: AnsiString;
begin
   getwindowtext (wnd, title, 256);
   s := AnsiString (pchar(@title));
   if (s <> '') and (list.indexof (string (s)) < 0) then
   begin
      win_name := PaString (s);
      receiverHandle := FindWindow (win_name, nil); // Find receiving app
      s := AnsiString (Format ('%s (%d)', [s, receiverHandle]));
      list.add (string (s));
   end; // if
   result:=true;
end;

procedure TSenderMainForm.Loaded;
begin
   inherited Loaded;

   enumwindows (@nextwindow, lparam (Log.Items)); {pass the list as a parameter}
end;

procedure TSenderMainForm.SendString (send_string: aString);
var copyDataStruct: TCopyDataStruct; { Declared in Windows.pas: TCopyDataStruct}
    receiverHandle: THandle;
    res: integer;
begin
// Copy string to CopyDataStruct
   copyDataStruct.dwData := 1; //use it to identify the message contents
   copyDataStruct.cbData := (1 + Length (send_string)) * SizeOf (Char);
   copyDataStruct.lpData := PaString (send_string);

   receiverHandle := FindWindow (PaString (cClassName), nil); // Find receiving app
   if receiverHandle = 0 then // not found
   begin
      Log.Items.Add ('CopyData Receiver NOT found!');
   end else // found, send message
   begin
      res := SendMessage (receiverHandle, WM_COPYDATA, Integer(Handle), Integer(@copyDataStruct));
      Log.Items.Add (Format ('String sent, len = %d, result = %d', [copyDataStruct.cbData, res]));
      Log.Items.Add ('"' + PaString (copyDataStruct.lpData) + '"');
   end; // if
end; // SendString

procedure TSenderMainForm.Button_Send_DataClick (Sender: TObject);
begin
   SendString (ParamStr (0));
end;
    ====================== Unit copyDataReceiver ================
unit ReceiverMain;
{ How to send information (String, Image, Record) between two Delphi applications
http://delphi.about.com/od/windowsshellapi/a/wm_copydata.htm }
interface

uses
   Windows, Messages,
   SysUtils, Variants, Classes, Graphics, Controls, Forms,
   Dialogs, StdCtrls, ExtCtrls, shared_data;

type
  TReceiverMainForm = class (TForm)
    Log: TListBox;

    procedure FormCreate(Sender: TObject);

  private
    procedure WMCopyData (var Msg: TWMCopyData); message WM_COPYDATA;
    procedure WMSignalClose (var Msg: TMessage);  message WM_SIGNAL_CLOSE;

    procedure HandleCopyDataString (copyDataStruct: PCopyDataStruct);
  end;

var ReceiverMainForm: TReceiverMainForm;

implementation

{$R *.dfm}

procedure TReceiverMainForm.FormCreate (Sender: TObject);
begin
  Log.Clear;
end;

procedure TReceiverMainForm.WMSignalClose (var Msg: TMessage);
var pfn: PaString;
    fn: aString;
begin
   Log.Items.Add (Format ('Signal received, WParam = %d, LParam = %d', [Msg.WParam, Msg.LParam]));
   pfn := PaString (Msg.LParam);
   fn  := aString (pfn);
   Log.Items.Add (fn);
end;

procedure TReceiverMainForm.WMCopyData (var Msg: TWMCopyData);
var copyDataType: Int32;
begin
   copyDataType := Msg.CopyDataStruct.dwData;

   //Handle of the Sender
   Log.Items.Add (Format ('WM_CopyData (type: %d) from: %d', [copyDataType, msg.From]));
   HandleCopyDataString (Msg.CopyDataStruct);

   //Send something back
   msg.Result := Log.Items.Count;
end;

procedure TReceiverMainForm.HandleCopyDataString (copyDataStruct: PCopyDataStruct);
var mess: aString;
begin
   mess := aString (PaString (copyDataStruct.lpData));
   Log.Items.Add (Format ('Received string of length %d at %s', [Length (mess), DateToStr (Now)]));
   Log.Items.Add ('"' + mess + '"');
end;

end.
    ================ unit shared_data ==========================
unit shared_data;

interface

uses Messages;

const
   WM_SIGNAL_CLOSE = WM_APP + 2012;
   ARG_AMI_1       = 285;
   ARG_AMI_2       = 1;
   cClassName      = 'TReceiverMainForm';

type
   aString  = string;
   PaString = PChar;

implementation

end.

发送方应用程序的关键是它向接收方发送WM_COPYDATA。为了找到接收器，FindWindow与接收应用程序的名称（硬编码）一起使用，它返回窗口的句柄。如果句柄为零，则显示错误。

当我在FMX应用程序中复制它时会出现问题。 FMX接收部件不起作用，而VCL接收器可以从VCL发送器或FMX发送器接收消息。 FMX接收器的代码如下所示。

因为我不确定窗口的名称，所以我列举了所有窗口，为每个窗口名称添加了数字句柄，并将其显示在发件人的列表框中。所有句柄都为零。我有两个问题：

为什么枚举中的所有句柄都为零？
为什么我无法向FMX接收申请发送消息？

非常感谢任何帮助。

unit copyDataReceiver;

interface

uses
   System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
   FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.Layouts, FMX.ListBox,
   Windows, Messages, shared_data;

type
   TReceiverMainForm = class (TForm)
    Log: TListBox;

    procedure FormCreate(Sender: TFMXObject);

  private
    procedure WMCopyData (var Msg: TWMCopyData); message WM_COPYDATA;
    procedure WMSignalClose (var Msg: TMessage);  message WM_SIGNAL_CLOSE;

    procedure HandleCopyDataString (copyDataStruct: PCopyDataStruct);
  end;

var ReceiverMainForm: TReceiverMainForm;

implementation

{$R *.fmx}

procedure TReceiverMainForm.FormCreate (Sender: TFMXObject);
begin
  Log.Clear;
end;

procedure TReceiverMainForm.WMSignalClose (var Msg: TMessage);
var pfn: PaString;
    fn: aString;
begin
   Log.Items.Add (Format ('Signal received, WParam = %d, LParam = %d', [Msg.WParam, Msg.LParam]));
   pfn := PaString (Msg.LParam);
   fn  := aString (pfn);
   Log.Items.Add (fn);
end;

procedure TReceiverMainForm.WMCopyData (var Msg: TWMCopyData);
var copyDataType: Int32;
begin
   copyDataType := Msg.CopyDataStruct.dwData;

   //Handle of the Sender
   Log.Items.Add (Format ('WM_CopyData (type: %d) from: %d', [copyDataType, msg.From]));
   HandleCopyDataString (Msg.CopyDataStruct);

   //Send something back
   msg.Result := Log.Items.Count;
end;

procedure TReceiverMainForm.HandleCopyDataString (copyDataStruct: PCopyDataStruct);
var mess: aString;
begin
   mess := aString (PaString (copyDataStruct.lpData));
   Log.Items.Add (Format ('Received string of length %d at %s', [Length (mess), DateToStr (Now)]));
   Log.Items.Add ('"' + mess + '"');
end;

end.

Answer 1

FindWindow在FMX下的工作原理相同。问题是将消息发送到您找到的窗口不会导致它们被路由到表单的消息处理程序。

相反，即使使用VCL，你也应该做你应该做的事情。这是使用一个已知的窗口，你可以控制它的寿命。请记住，VCL窗口需要重新创建。换句话说，您可能在另一个进程中有一个窗口的窗口句柄，但在您有机会向其发送消息之前，该窗口可能会被销毁。

使用AllocateHWnd或CreateWindow解决此问题，以创建一个不会重新创建的窗口。一个窗口，你可以控制它的生命您必须为其他进程设计一种方法来发现您的窗口。我个人会将CreateWindow与已知的类名一起使用，然后使用EnumWindows枚举顶级窗口，查找该类名称的窗口。

Answer 2

为什么我不能向接收申请的FMX发送消息？

对于VCL表单，ClassName是通过简单地从表单名称派生的在名称前添加前导“ T”。例如如果您有一个名为MyForm的窗体，则ClassName为TMyForm。 Self.ClassName返回此名称和对 Winapi.Windows.FindWindow(PChar(Self.ClassName), nil)返回正确的处理。

使用FMX-Forms，您将收到以类似方式构建的ClassName。对于FMX-Forms，ClassName是通过以下方式从表单名称派生的：在表格名称中添加前导“ FMT”。 Self.ClassName返回的ClassName与VCL-Forms相同。

例如如果您有一个名为MyFMXForm的窗体，则ClassName为FMTMyFMXForm，但是 Self.ClassName返回TMyFMXForm。因此，尝试获取具有该ClassName的窗口句柄失败。正确的电话是 Winapi.Windows.FindWindow(PChar('FMTMyFMXForm'), nil));。

FindWindow在FMX中工作吗？

2 个答案: