使用SendMessage将文本从VB发送到Delphi应用程序

Question

)我试图从VB应用程序发送一个简短的文本到Delphi应用程序..这是VB代码:发件人程序"发件人"

Public Class SendData

 Const WM_COPYDATA = &H4A
 Public Structure CopyDataStruct
    Public dwData As Integer
    Public cbData As Integer
    Public lpData As String
 End Structure

Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
 (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Declare Function SendMessage Lib "user32" Alias "SendMessageA" _ 
 (ByVal hWnd As Long,  ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As _
 CopyDataStruct) As Long

Private Sub SendData(ByVal cds)
    Dim iHwnd As Long
    Dim SS As String = "Test String less than 30 Char"
    Dim cds As CopyDataStruct
    cds.dwData = 0
    cds.cbData = Len(SS)
    cds.lpData = SS
    iHwnd = FindWindow(0&, "Receive")
    SendMessage(iHwnd, &H4A, Me.Handle, cds) 
End Sub

这里是德尔福代码:接收程序"接收"

 procedure TForm1.HandleCopyDataString(copyDataStruct: PCopyDataStruct);
 var
  s : string;
 begin
  s := PChar(CopyDataStruct.lpData);
  cdMemo.Lines.Add(Format('Received data "%s" at %s',[s, TimeToStr(Now)]));
 end;

 procedure TForm1.WMCopyData(var Msg: TWMCopyData) ;
 var
  s : string;
  sText: array[0..255] of Char;
  copyDataType : TCopyDataType;
 begin
  copyDataType := TCopyDataType(Msg.CopyDataStruct.dwData);
  s := PChar(Msg.CopyDataStruct.dwData);
  Form1.cdMemo.Lines.Add(Format('Data from: %d',[msg.From]));
  HandleCopyDataString(Msg.CopyDataStruct);
  case Msg.CopyDataStruct.dwData of 0: //we are being sent a string
  begin
    StrLCopy(sText, Msg.CopyDataStruct.lpData, Msg.CopyDataStruct.cbData);
    Form1.Label1.Caption := sText;
  end;
end;
end;

我在这做错了什么？可以使用WM_COPYDATA命令和SendMessage函数将字符串从VB发送到Delphi程序吗？

请帮我 :-)

F

Answer 1

您的Delphi代码有一些问题.

1. 该dwData字段包含一个整数,但您将其类型转换PChar为指针,然后将其分配给您的字符串.这不是存储字符串数据的字段.那是lpData.

2. 您传递的字符串不以空值终止.操作系统仅承诺复制与您在cbData字段中指定的字节数完全相同的字节数.这不一定是个问题,但是当你稍后阅读字符串时需要注意它.要指定s保存从其他进程复制的字符串,请使用SetString如下所示:

   SetString(s, PAnsiChar(Msg.CopyDataStruct.lpData), Msg.CopyDataStruct.cbData);
   

3. 你没有显示出什么TCopyDataType,但如果它不是整数或整数 - 子范围类型,你使用它是错误的.该dwData字段已经是a DWord,因此您可以在期望数值的任何地方使用它.

4. 你StrLCopy打错了.第三个参数应该是目标缓冲区的大小,而不是源.这意味着通过不复制比目标中适合的更多字符来防止缓冲区溢出.该函数希望能够通过查找终止空字符来检测源缓冲区的大小(但我们已经确定了该字符将不可用).你可以像这样解决它:

   StrLCopy(sText, Msg.CopyDataStruct.lpData,
     Min(Length(sText), Msg.CopyDataStruct.cbData));
   

   (Min在数学单元中.)