关于WM_SETFOCUS和WM_KILLFOCUS的问题

[htiep]

关于输入焦点的两个消息WM_SETFOCUS和WM_KILLFOCUS：是何时由谁产生？又由谁以怎样的操作来回应？多谢！

[元明]

这里我想给你举一个Win32中的例子,在VC中其实也是一样的.
请看代码:
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
.
.
.
switch(message) {
.
.
.
case WM_SETFOCUS:
//idFoucus子窗口句柄ID,此句话的意思为将子窗口设为当前的焦点.
SetFocus(GetDlgItem(hwnd,idFocus));
//返回操作系统
return 0;
case WM_KEYDOWN:
x = idFocus & 0xFF ;
y = idFocus >> 8 ;

switch (wParam)
{
case VK_UP: y-- ; break ;
case VK_DOWN: y++ ; break ;
case VK_LEFT: x-- ; break ;
case VK_RIGHT: x++ ; break ;
case VK_HOME: x = y = 0 ; break ;
case VK_END: x = y = DIVISIONS - 1 ; break ;
default: return 0 ;
}

x = (x + DIVISIONS) % DIVISIONS ;
y = (y + DIVISIONS) % DIVISIONS ;

idFocus = y << 8 | x ;

//向当前的消息队列中插入WM_SETFOCUS消息
SetFocus (GetDlgItem (hwnd, idFocus)) ;
return 0 ;
..
..
..
}
}


LRESULT CALLBACK ChildWndProc (HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam) {
..
..
..
switch (message) {
..
..
..
//子窗口捕获WM_SETFOCUS消息
case WM_SETFOCUS:
idFocus = GetWindowLong (hwnd, GWL_ID) ;

// Fall through
//当子窗口失去焦点是响应,同时这个消息承接上个消息,因为WM_SETFOCUS并没有
//return语句
case WM_KILLFOCUS:
InvalidateRect (hwnd, NULL, TRUE) ;
return 0 ;
}
}

以上代码我都加了必要的注释,不知你看懂了没有.
下面我把源代码整个附出,以帮助你理解.
/*-------------------------------------------------
CHECKER4.C -- Mouse Hit-Test Demo Program No. 4
(c) Charles Petzold, 1998
-------------------------------------------------*/

#include <windows.h>

#define DIVISIONS 5

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
LRESULT CALLBACK ChildWndProc (HWND, UINT, WPARAM, LPARAM) ;

int idFocus = 0 ;
TCHAR szChildClass[] = TEXT ("Checker4_Child") ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("Checker4") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;

wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;

if (!RegisterClass (&wndclass))
{
MessageBox (NULL, TEXT ("Program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}

wndclass.lpfnWndProc = ChildWndProc ;
wndclass.cbWndExtra = sizeof (long) ;
wndclass.hIcon = NULL ;
wndclass.lpszClassName = szChildClass ;

RegisterClass (&wndclass) ;

hwnd = CreateWindow (szAppName, TEXT ("Checker4 Mouse Hit-Test Demo"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL) ;

ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;

while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static HWND hwndChild[DIVISIONS][DIVISIONS] ;
int cxBlock, cyBlock, x, y ;

switch (message)
{
case WM_CREATE :
for (x = 0 ; x < DIVISIONS ; x++)
for (y = 0 ; y < DIVISIONS ; y++)
hwndChild[x][y] = CreateWindow (szChildClass, NULL,
WS_CHILDWINDOW | WS_VISIBLE,
0, 0, 0, 0,
hwnd, (HMENU) (y << 8 | x),
(HINSTANCE) GetWindowLong (hwnd, GWL_HINSTANCE),
NULL) ;
return 0 ;

case WM_SIZE :
cxBlock = LOWORD (lParam) / DIVISIONS ;
cyBlock = HIWORD (lParam) / DIVISIONS ;

for (x = 0 ; x < DIVISIONS ; x++)
for (y = 0 ; y < DIVISIONS ; y++)
MoveWindow (hwndChild[x][y],
x * cxBlock, y * cyBlock,
cxBlock, cyBlock, TRUE) ;
return 0 ;

case WM_LBUTTONDOWN :
MessageBeep (0) ;
return 0 ;

// On set-focus message, set focus to child window

case WM_SETFOCUS:
SetFocus (GetDlgItem (hwnd, idFocus)) ;
return 0 ;

// On key-down message, possibly change the focus window

case WM_KEYDOWN:
x = idFocus & 0xFF ;
y = idFocus >> 8 ;

switch (wParam)
{
case VK_UP: y-- ; break ;
case VK_DOWN: y++ ; break ;
case VK_LEFT: x-- ; break ;
case VK_RIGHT: x++ ; break ;
case VK_HOME: x = y = 0 ; break ;
case VK_END: x = y = DIVISIONS - 1 ; break ;
default: return 0 ;
}

x = (x + DIVISIONS) % DIVISIONS ;
y = (y + DIVISIONS) % DIVISIONS ;

idFocus = y << 8 | x ;

SetFocus (GetDlgItem (hwnd, idFocus)) ;
return 0 ;

case WM_DESTROY :
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}

LRESULT CALLBACK ChildWndProc (HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
{
HDC hdc ;
PAINTSTRUCT ps ;
RECT rect ;

switch (message)
{
case WM_CREATE :
SetWindowLong (hwnd, 0, 0) ; // on/off flag
return 0 ;

case WM_KEYDOWN:
// Send most key presses to the parent window

if (wParam != VK_RETURN && wParam != VK_SPACE)
{
SendMessage (GetParent (hwnd), message, wParam, lParam) ;
return 0 ;
}
// For Return and Space, fall through to toggle the square

case WM_LBUTTONDOWN :
SetWindowLong (hwnd, 0, 1 ^ GetWindowLong (hwnd, 0)) ;
SetFocus (hwnd) ;
InvalidateRect (hwnd, NULL, FALSE) ;
return 0 ;

// For focus messages, invalidate the window for repaint

case WM_SETFOCUS:
idFocus = GetWindowLong (hwnd, GWL_ID) ;

// Fall through

case WM_KILLFOCUS:
InvalidateRect (hwnd, NULL, TRUE) ;
return 0 ;

case WM_PAINT :
hdc = BeginPaint (hwnd, &ps) ;

GetClientRect (hwnd, &rect) ;
Rectangle (hdc, 0, 0, rect.right, rect.bottom) ;

// Draw the "x" mark

if (GetWindowLong (hwnd, 0))
{
MoveToEx (hdc, 0, 0, NULL) ;
LineTo (hdc, rect.right, rect.bottom) ;
MoveToEx (hdc, 0, rect.bottom, NULL) ;
LineTo (hdc, rect.right, 0) ;
}

// Draw the "focus" rectangle

if (hwnd == GetFocus ())
{
rect.left += rect.right / 10 ;
rect.right -= rect.left ;
rect.top += rect.bottom / 10 ;
rect.bottom -= rect.top ;

SelectObject (hdc, GetStockObject (NULL_BRUSH)) ;
SelectObject (hdc, CreatePen (PS_DASH, 0, 0)) ;
Rectangle (hdc, rect.left, rect.top, rect.right, rect.bottom) ;
DeleteObject (SelectObject (hdc, GetStockObject (BLACK_PEN))) ;
}

EndPaint (hwnd, &ps) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}

[luxes]

WM_SETFOCUS是在得到焦点之后由系统发给窗口的；
WM_KILLFOCUS是在失去焦点之前由系统发给窗口的。
你可以子类化一个EDIT，响应这两个消息体会体会。

[htiep]

多谢magicwizard和luxes！
magicwizard顺便问一句：你是不是也有一本北大出版的WINDOWS程序设计？今天我刚刚看完第六章，我觉得在看过的几章内有几个难点，不知后面是否还有难点？以后还请多多指教！

[元明]

我确实有一本,但在看的时候也遇到了不少难点,我很希望与你一起交流,我等着你的来信,一块来学习吧!对了,你VC学的怎么样,盼你的回音!!
[e-mail]