WM_COPYDATA string not appearing in target application
I'm trying to pass information between two of my applications in Delphi 2010.
I'm using a simplified version of code that I've used successfully in the past (simplified because I don't need the sender to know that the send has been successful) I've boiled down the send received to a pair of example applications, which in essence are as follows
Send
procedure TMF.SendSt开发者_Go百科ring;
var
copyDataStruct: TCopyDataStruct;
s: AnsiString;
begin
s := ebFirm.Text;
copyDataStruct.cbData := 1 + length(s);
copyDataStruct.lpData := PAnsiChar(s);
SendData(copyDataStruct);
end;
procedure TMF.SendData(copyDataStruct: TCopyDataStruct);
var
rh: THandle;
res: integer;
begin
rh := FindWindow(PChar('TMF'), PChar('Get Phone'));
if rh = 0 then
begin
// Launch the target application
ShellExecute(Handle, 'open', GetPhone, nil, nil, SW_SHOWNORMAL);
// Give time for the application to launch
Sleep(3000);
SendData(copyDataStruct); // RECURSION!
end;
SendMessage(rh, WM_COPYDATA, Integer(Handle), Integer(@copyDataStruct));
end;
Receive Application
procedure TMF.WMCopyData(var Msg: TWMCopyData);
var
s : AnsiString;
begin
s := PAnsiChar(Msg.CopyDataStruct.lpData) ;
jobstatus.Panels[1].Text := s;
end;
The major difference between the working test applications and the application I am adding the code to is that there is a lot of extra activity going on in target application. Especially on startup.
Any suggestions on why the WMCopyData procedure seems not to be firing at all?
CHeers
Dan
There are a few problems with your code.
One, you are not assigning a unique ID to the message. The VCL, and various third-party components, also use WM_COPYDATA
, so you have to make sure you are actually processing YOUR message and not SOMEONE ELSE'S message.
Two, you may not be waiting long enough for the second app to start. Instead of Sleep()
, use ShellExecuteEx()
with the SEE_MASK_WAITFORINPUTIDLE
flag (or use CreateProcess()
and WaitForInputIdle()
).
Third, when starting the second app, your recursive logic is attempting to send the message a second time. If that happened to fail, you would launch a third app, and so on. You should take out the recursion altogether, you don't need it.
Try this:
var
GetPhoneMsg: DWORD = 0;
procedure TMF.SendString;
var
copyDataStruct: TCopyDataStruct;
s: AnsiString;
begin
if GetPhoneMsg = 0 then Exit;
s := ebFirm.Text;
copyDataStruct.dwData := GetPhoneMsg;
copyDataStruct.cbData := Length(s);
copyDataStruct.lpData := PAnsiChar(s);
SendData(copyDataStruct);
end;
procedure TMF.SendData(copyDataStruct: TCopyDataStruct);
var
rh: HWND;
si: TShellExecuteInfo;
res: Integer;
begin
rh := FindWindow(PChar('TMF'), PChar('Get Phone'));
if rh = 0 then
begin
// Launch the target application and give time to start
ZeroMemory(@si, SizeOf(si));
si.cbSize := SizeOf(si);
si.fMask := SEE_MASK_WAITFORINPUTIDLE;
si.hwnd := Handle;
si.lpVerb := 'open';
si.lpFile := GetPhone;
si.nShow := SW_SHOWNORMAL;
if not ShellExecuteEx(@si) then Exit;
rh := FindWindow(PChar('TMF'), PChar('Get Phone'));
if rh = 0 then Exit;
end;
SendMessage(rh, WM_COPYDATA, WParam(Handle), LParam(@copyDataStruct));
end;
initialization
GetPhoneMsg := RegisterWindowMessage('TMF_GetPhone');
Receive Application
var
GetPhoneMsg: DWORD = 0;
procedure TMF.WMCopyData(var Msg: TWMCopyData);
var
s : AnsiString;
begin
if (GetPhoneMsg <> 0) and (Msg.CopyDataStruct.dwData = GetPhoneMsg) then
begin
SetString(s, PAnsiChar(Msg.CopyDataStruct.lpData), Msg.CopyDataStruct.cbData);
jobstatus.Panels[1].Text := s;
end else
inherited;
end;
initialization
GetPhoneMsg := RegisterWindowMessage('TMF_GetPhone');
I think it is a good habit to add
copyDataStruct.dwData := Handle;
in procedure TMF.SendString;
- if you don't have a custom identifier, putting the source HWND value will help debugging on the destination (you can check for this value in the other side, and therefore avoid misunderstand of broadcasted WMCOPY_DATA e.g. - yes, there should not be, but I've seen some!).
And
procedure WMCopyData(var Msg : TWMCopyData); message WM_COPYDATA;
in TMF
client class definition, right?
There should be a missing exit
or else
after the nested SendData
call:
procedure TMF.SendData(copyDataStruct: TCopyDataStruct);
(...)
Sleep(3000);
SendData(copyDataStruct);
end else
SendMessage(rh, WM_COPYDATA, NativeInt(Handle), NativeInt(@copyDataStruct));
end;
But this won't change much.
Check the rh := FindWindow()
returned handle: is it the Handle of the TMF
client form, or the Application.Handle?
It doesn't work anymore if you are using Windows 7. If you are using it, check this page to see how to add an exception: http://msdn.microsoft.com/en-us/library/ms649011%28v=vs.85%29.aspx
I thought there was a problem with the (rh) handle being 0 when you call it, if the app needed to be started. But now I see that SendData calls itself recursively. I added a comment in the code for that, as it was non-obvious. But now there's another problem. The 2nd instance of SendData will have the right handle. But then you're going to pop out of that, back into the first instance where the handle is still 0, and then you WILL call SendMessage again, this time with a 0 handle. This probably is not the cause of your trouble, but it's unintended, unnecessary, and altogether bad. IMO, this is a case complicating things by trying to be too clever.
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