根据进程名获取对应窗口大小，为什么会失败呢？

根据进程名获取对应窗口大小，为什么会失败呢？请求帮助！！！
代码片段：
var
  hCurrentWindow: THandle;
  MyHandle: THandle;
  WinRect,WinRect2: TRect;

{使用GetForegroundWindow方法得到当前窗口句柄后可以获取到正确的大小}
hCurrentWindow := GetForegroundWindow();
GetWindowRect(hCurrentWindow, WinRect);

{而通过进程名得到句柄后却不能获取正确的窗口大小，为什么呢？}
MyHandle := GetProcess('Project1.exe'); //GetProcess为自定义获取进程句柄的函数
GetWindowRect(MyHandle, WinRect2);

而且发现这两种方法得到的句柄值也不同，在我本机测试数据如下：
hCurrentWindow=1248932
MyHandle=1708

请问是什么原因呢？这2个句柄有何区别，又该如何解决呢？请高手指点一二，感激不尽！



以下是完整的代码（Unit1.pas）：

****************************************************************************************
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, SvcMgr, Dialogs,
  ExtCtrls, Registry, ScktComp, PsAPI, Forms, WinInet, Sockets, StdCtrls;

type
  TForm1 = class(TForm)
  Button1: TButton;
  procedure Button1Click(Sender: TObject);  
  function GetProcess(aProcessName: String):THandle;
  private
  { Private declarations }
  public
  { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  hCurrentWindow: THandle;
  MyHandle: THandle;
  WinRect,WinRect2: TRect;
begin
  hCurrentWindow := GetForegroundWindow();
  GetWindowRect(hCurrentWindow, WinRect);
  showmessage('Handle1=' + inttostr(hCurrentWindow)
  + ',size1=' + inttostr(WinRect.Right - WinRect.Left) + ','
  + inttostr(WinRect.Bottom - WinRect.Top));

  MyHandle := GetProcess('Project1.exe');
  GetWindowRect(MyHandle, WinRect2);
  showmessage('Handle2=' + inttostr(MyHandle)
  + ',size2=' + inttostr(WinRect2.Right - WinRect2.Left) + ','
  + inttostr(WinRect2.Bottom - WinRect2.Top));
end;

//¸ù¾Ý½ø³ÌÃû»ñÈ¡¶ÔÓ¦½ø³ÌµÄhandle
function TForm1.GetProcess(aProcessName: String):THandle;
type
  integer = DWORD;
var
  i,pidNeeded: Integer;
  PIDList: array[0..1000] of Integer;
  PIDName: array[0..MAX_PATH - 1] of char;
  PH: THandle;
begin
  Result := 0;
  if not PsAPI.EnumProcesses(@PIDList, 1000, pidNeeded) then
  begin
  exit;
  end;
  for i := 0 to (pidNeeded div sizeof(Integer) - 1) do
  begin
  PH := OpenProcess(PROCESS_QUERY_INFORMATION or PROCESS_VM_READ, False, PIDList[i]);
  if PH <> 0 then
  begin
  if PsAPI.GetModuleBaseName(PH, 0, PIDName, sizeof(PIDName)) > 0 then
  if aProcessName = pidName then
  begin
  Result := PH;
  end;
  if PH > 0 then closeHandle(PH);
  if Result = PH then break;
  end;
  end;
end;


end.
****************************************************************************************

[解决办法]
晕，进程句柄和窗体句柄简直就是风马牛不相及
[解决办法]
根据我的经验
应该把一个窗体句柄分为两个来看
一个是在本进程映射的句柄
一个是在全局中映射的句柄
两个句柄的值是不一样的
[解决办法]
function EnumWinFun(AHandle: THandle; AID: DWORD):boolean; stdcall;
var

m_Caption: array[0..255] of char;
m_WinRect, m_ClientRect: TRect;
begin
if (GetWindowThreadProcessId(AHandle, nil) = AID) then
begin
GetWindowText(AHadle, m_Caption, 256);
//GetWindowRect(AHandle, m_WinRect); //获取窗体矩形区域
//GetClientRect(AHandle, m_ClientRect);//获取窗体客户区域
MessageBox(0, PChar(m_Caption), 'Find Window!', MB_OK);
end;

Result:= true;
end;

//枚举当前进程中所有的窗体
procedure TForm1.Button1Click(Sender: TObject);
begin
//这里，更改第二个参数（改为你想获取窗体的进程句柄），就可以枚举其他进程的窗体，
EnumWindows(@EnumWinFun, GetCurrentProcessID);
end;
[解决办法]
EnumWindows(@EnumWinFun, GetProcess( "Project1.exe ")); 

GetProcess函数传递的应是PROCESSID 是ID 不是句柄，晕！

 AID====GetCurrentProcessID

 if (GetWindowThreadProcessId(AHandle, nil) = AID) then 

[解决办法]
agree with lxtnt

Enumberate all window handles, use GetWindowThreadProcessID to get the process id