确定你已在在你的主窗体对象中加入了下面的变量:
FClientInstance : TFarProc;
FPrevClientProc : TFarProc;


{ MDI的背景代码 }
procedure TMainForm.ClientWndProc(var Message: TMessage);
var
Dc : hDC;
Row : Integer;
Col : Integer;
begin
with Message do
case Msg of
WM_ERASEBKGND:
begin
Dc := TWMEraseBkGnd(Message).Dc;
// 在DC上平铺图象
for Row := 0 to ClientHeight div Image1.Picture.Height do
for Col := 0 to ClientWidth div Image1.Picture.Width do
BitBlt(Dc,
Col * Image1.Picture.Width,
Row * Image1.Picture.Height,
Image1.Picture.Width,
Image1.Picture.Height,
Image1.Picture.Bitmap.Canvas.Handle,
0,
0,
SRCCOPY);
Result := 1;
end;
else // 传递其他消息
Result := CallWindowProc(FPrevClientProc,
ClientHandle,
Msg,
wParam,
lParam);
end;
end;


- 在你的主窗体的OnShow事件中加入以下代码:

// MDI背景平铺代码，与WndProc链接
FClientInstance := MakeObjectInstance(ClientWndProc);
FPrevClientProc := Pointer(GetWindowLong(ClientHandle,GWL_WNDPROC));
SetWindowLong(ClientHandle,GWL_WNDPROC,LongInt(FClientInstance));

- 现在你有一个背景了!