大家都知道每个窗口都有默认的窗口函数来进行对窗口消息的处理.
而子类化技术就是替换窗口的窗口函数为自己定义的函数的技术.例如下面的代码:
var
Form1: TForm1;
OldWndProc: Pointer;
implementation
{$R *.dfm}
function NewWndProc(hHwnd, Msg, wParam, lParam: LongWORD): Longint; stdcall;
begin
if Msg=WM_CLOSE then
exit;
Result := CallWindowProc(OldWndProc, hHwnd, Msg, wParam, lParam);
end;
{------------------------------------}
{过程名:DLL入口函数
{过程功能:进行DLL初始化,释放等
{过程参数:DLL状态
{------------------------------------}
procedure MyDLLHandler(Reason: Integer);
var
FHandle: LongWORD;
begin
case Reason of
DLL_PROCESS_ATTACH:
begin {建立文件映射,以实现DLL中的全局变量}
FHandle := CreateFileMapping($FFFFFFFF, nil, PAGE_READWRITE, 0, $ff, 'MYDLLDATA');
if FHandle = 0 then
if GetLastError = ERROR_ALREADY_EXISTS then
begin
FHandle := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, 'MYDLLDATA');
if FHandle = 0 then Exit;
end else Exit;
DLLData := MapViewOfFile(FHandle, FILE_MAP_ALL_ACCESS, 0, 0, 0);
if DLLData = nil then
CloseHandle(FHandle);
end;
DLL_PROCESS_DETACH:
if Assigned(DLLData) then
begin
UnmapViewOfFile(DLLData);
DLLData := nil;
end;
DLL_THREAD_ATTACH:;
DLL_THREAD_DETACH:;
end;
end;
{$R *.res}
exports
InstallHook, UnHook, HookProc;
begin
DLLProc := @MyDLLHandler;
MyDLLhandler(DLL_PROCESS_ATTACH);
end.