用法如下：

　　nParentHandle: HWnd;
　　nChildHandle: HWnd;

　　nParentHandle := FindWindow(nil, ''Notepad'');
　　if nParentHandle <> 0 then
　　　　nChildHandle := FindChildWindow(nParentHandle, ''SomeChildEditsClassName'');

------函數代碼------

var
hwndFindChildWindow : HWND;

function EnumWindowsForFindChildWindowProc(WHandle: HWND; lParam: LPARAM): BOOL; export; stdcall;
const
MAX_WINDOW_NAME_LEN = 80;
var
sTargetClassName: string;
nHandle: HWnd;
sCurrClassName: string;
bResult: Boolean;
begin
if (hwndFindChildWindow <> 0) then
exit;
sTargetClassName := PChar(lParam);
sCurrClassName := GetWindowClass(WHandle);
bResult := CompareText(sCurrClassName, sTargetClassName) = 0;
If (bResult) then
hwndFindChildWindow := WHandle
else
FindChildWindow(WHandle, PChar(lParam));
end;

function FindChildWindow(hwndParent: HWnd; ClassName: PChar) : HWnd;
begin
try
EnumChildWindows(hwndParent, @EnumWindowsForFindChildWindowProc, LongInt(PChar(ClassName)));
Result := hwndFindChildWindow;
except
on Exception do
Result := 0;
end;
end;

//返回當前獲得焦點的窗體
function GetFocusedWindowFromParent(ParentWnd:HWnd):HWnd;
var
OtherThread,
Buffer : DWord;
idCurrThread: DWord;
begin
OtherThread := GetWindowThreadProcessID(ParentWnd, @Buffer);
idCurrThread := GetCurrentThreadID;
if AttachThreadInput(idCurrThread, OtherThread, true) then begin
Result := GetFocus;
AttachThreadInput(idCurrThread, OtherThread, false);
end
else
Result:= GetFocus;
end;

//獲得當前獲得焦點的子窗體，即使它是其他應用程序的窗體
function GetFocusedChildWindow: HWnd;
begin
Result := GetFocusedWindowFromParent(GetForegroundWindow);
end;

//獲得窗體的文本
function EIGetWinText(nHandle: Integer): string;
var
pcText: array[0..32768] of char;
begin
SendMessage(nHandle, WM_GETTEXT, 32768, LongInt(@pcText));
Result := pcText;
end;

//設定窗體的文本
procedure EISetWinText(nHandle: Integer; const sNewText: string);
begin
SendMessage(nHandle, WM_SETTEXT, Length(sNewText), LongInt(PChar(Trim(sNewText))));
end;

//返回窗體的類名
function EIGetWindowClass(const nHandle: HWnd): string;
var
szClassName: array[0..255] of char;
begin
GetClassName(nHandle, szClassName, 255);
Result := szClassName;
end;