Process ID, Process handle, Window handle

http://forums.codeguru.com/showthread.php?392273-RESOLVED-How-to-get-window-s-HWND-from-it-s-process-handle

I am confused about what you know and what you still need to know. Some of your statements seem to be contradicting, so I will tell you some possibilities:

1)
HAVE: Process ID, NEED: Process handle
Solution: OpenProcess()

2)
HAVE: Process handle, NEED: Process ID
Solution: GetProcessId()

3)
HAVE: Window handle, NEED: Process ID
Solution: GetWindowThreadProcessId()

4)
HAVE: Window handle, NEED: Process handle
Solution: Use 3) and then 1)

5)
HAVE: Process ID, NEED: Window handle
Solution: EnumWindows(), then in the callback function do 3) and check if it matches your process ID.

6)
HAVE: Process handle, NEED: Window handle
Solution: 2) and then 5)

http://www.programlife.net/get-main-window-handler-in-dll.html

有的时候难免需要在DLL中获取主进程的窗口句柄，比如在DLL注入的时候等等。那么如何在DLL中获取主进程的窗口句柄呢？可以通过EnumWindows来实现。先通过GetCurrentProcessId获取进程的PID，然后在EnumWindows中调用GetWindowThreadProcessId获得与窗口句柄关联的进程PID，然后对比PID，看是否相等，并判断是不是主窗口即可。
以上方法参考自网络，不一定很完善，但是通常情况下已经够用了。附上测试代码：

// Author: 代码疯子
// Blog: http://www.programlife.net/
#include <windows.h>

BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
{
    DWORD dwCurProcessId = *((DWORD*)lParam);
    DWORD dwProcessId = ; 

    GetWindowThreadProcessId(hwnd, &dwProcessId);
    if(dwProcessId == dwCurProcessId && GetParent(hwnd) == NULL)
    {
        *((HWND *)lParam) = hwnd;
        return FALSE;
    }
    return TRUE;
} 

HWND GetMainWindow()
{
    DWORD dwCurrentProcessId = GetCurrentProcessId();
    if(!EnumWindows(EnumWindowsProc, (LPARAM)&dwCurrentProcessId))
    {
        return (HWND)dwCurrentProcessId;
    }
    return NULL;
} 

BOOLEAN WINAPI DllMain(
        IN HINSTANCE hDllHandle,
        IN DWORD     nReason,
        IN LPVOID    Reserved)
{
    BOOLEAN bSuccess = TRUE;

    switch ( nReason )
    {
    case DLL_PROCESS_ATTACH:
        MessageBox(GetMainWindow(), TEXT("OMG~ You are Attacked!"), TEXT("Warning"), MB_ICONWARNING);
        break;

    case DLL_PROCESS_DETACH:
        break;
    }

    return bSuccess;
}

ProcessID, Process Handle, Window Handle 之间的互相转换

http://www.delphitop.com/html/jincheng/219.html

// Get ProcessID By ProgramName (Include Path or Not Include)
function GetPIDByProgramName(const APName: string): THandle;
// Get Window Handle By ProgramName (Include Path or Not Include)
function GetHWndByProgramName(const APName: string): THandle;
// Get Window Handle By ProcessID
function GetHWndByPID(const hPID: THandle): THandle;
// Get ProcessID By Window Handle
function GetPIDByHWnd(const hWnd: THandle): THandle;
// Get Process Handle By Window Handle
function GetProcessHndByHWnd(const hWnd: THandle): THandle;
// Get Process Handle By Process ID
function GetProcessHndByPID(const hAPID: THandle): THandle;

// Get Window Handle By ProgramName (Include Path or Not Include)
function GetHWndByProgramName(const APName: string): THandle;
begin
Result:=GetHWndByPID(GetPIDByProgramName(APName));
end;

// Get Process Handle By Window Handle
function GetProcessHndByHWnd(const hWnd: THandle): THandle;
var
PID: DWORD;
AhProcess: THandle;
begin
if hWnd<> then
begin
GetWindowThreadProcessID(hWnd, @PID);
AhProcess := OpenProcess(PROCESS_ALL_ACCESS, false, PID);
Result:=AhProcess;
CloseHandle(AhProcess);
end
else
Result:=;
end;

// Get Process Handle By Process ID
function GetProcessHndByPID(const hAPID: THandle): THandle;
var
AhProcess: THandle;
begin
if hAPID<> then
begin
AhProcess := OpenProcess(PROCESS_ALL_ACCESS, false, hAPID);
Result:=AhProcess;
CloseHandle(AhProcess);
end
else
Result:=;
end;

// Get Window Handle By ProcessID
function GetPIDByHWnd(const hWnd: THandle): THandle;
var
PID: DWORD;
begin
if hWnd<> then
begin
GetWindowThreadProcessID(hWnd, @PID);
Result:=PID;
end
else
Result:=;
end;

// Get Window Handle By ProcessID
function GetHWndByPID(const hPID: THandle): THandle;
type
PEnumInfo = ^TEnumInfo;
TEnumInfo = record
ProcessID: DWORD;
HWND: THandle;
end;

function EnumWindowsProc(Wnd: DWORD; var EI: TEnumInfo): Bool; stdcall;
var
PID: DWORD;
begin
GetWindowThreadProcessID(Wnd, @PID);
Result := (PID <> EI.ProcessID) or
(not IsWindowVisible(WND)) or
(not IsWindowEnabled(WND));

if not Result then EI.HWND := WND; //break on return FALSE 所以要反向檢查
end;

function FindMainWindow(PID: DWORD): DWORD;
var
EI: TEnumInfo;
begin
EI.ProcessID := PID;
EI.HWND := ;
EnumWindows(@EnumWindowsProc, Integer(@EI));
Result := EI.HWND;
end;
begin
if hPID<> then
Result:=FindMainWindow(hPID)
else
Result:=;
end;

// Get ProcessID By ProgramName (Include Path or Not Include)
function GetPIDByProgramName(const APName: string): THandle;
var
isFound: boolean;
AHandle, AhProcess: THandle;
ProcessEntry32: TProcessEntry32;
APath: array[..MAX_PATH] of char;
begin
try
Result := ;
AHandle := CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, );
ProcessEntry32.dwSize := Sizeof(ProcessEntry32);
isFound := Process32First(AHandle, ProcessEntry32);

while isFound do
begin
AhProcess := OpenProcess(PROCESS_QUERY_INFORMATION or PROCESS_VM_READ,
false, ProcessEntry32.th32ProcessID);
GetModuleFileNameEx(AhProcess, , @APath[], sizeof(APath));

if (UpperCase(StrPas(APath)) = UpperCase(APName)) or
(UpperCase(StrPas(ProcessEntry32.szExeFile)) = UpperCase(APName)) then
begin
Result := ProcessEntry32.th32ProcessID;
break;
end;
isFound := Process32Next(AHandle, ProcessEntry32);
CloseHandle(AhProcess);
end;
finally
CloseHandle(AHandle);
end;
end;