全局变量设置为什么无效？

[yaoxinchao]

设置定时器，SetTimer（），第一个参数传入全局变量main_window_handle无效，Debug调试看到main_window_handle值为0X00000000，和hwnd值不一样，说明在WinMain函数中对全局变量赋值无效，请问这是为什么呀？？？
// DEMO3_1.CPP - Demo of loading an icon and cursor resource

// INCLUDES ///////////////////////////////////////////////
#define WIN32_LEAN_AND_MEAN // just say no to MFC

#include <windows.h> // include all the windows headers
#include <windowsx.h> // include useful macros
#include <mmsystem.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include<tchar.h>
//#include "DEMO3_1RES.H" // include the resource header

// DEFINES ////////////////////////////////////////////////

// defines for windows
#define WINDOW_CLASS_NAME "WINCLASS1"
#define TIMER_ID_1SEC 1
#define TIMER_ID_3SEC 3

// GLOBALS ////////////////////////////////////////////////
HWND main_window_handle = NULL;
HINSTANCE main_instance = NULL;

#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)
#define KEYUP(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)

// FUNCTIONS //////////////////////////////////////////////

//LRESULT CALLBACK TimerProc(HWND)
LRESULT CALLBACK WindowProc(HWND hwnd,
UINT msg,
WPARAM wparam,
LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT ps; // used in WM_PAINT
HDC hdc; // handle to a device context
TCHAR buffer[80];

static int counter1=0, // counters
counter3=0;

// what is the message
switch(msg)
{
case WM_CREATE:
{
// do initialization stuff here
////设置定时器
SetTimer(hwnd,TIMER_ID_1SEC,1000,NULL); ///////这里用全局变量main_window_handle为什么不行
SetTimer(hwnd,TIMER_ID_3SEC,3000,NULL);
// return success
return(0);
} break;

case WM_TIMER:
{
////what timer fired?
switch(wparam)
{
case TIMER_ID_1SEC:
{
//MessageBox(hwnd,TEXT("timer 1 fired!"),"Timer 1",MB_OK);
// print out a message
// get the dc
hdc = GetDC(hwnd);

// set the color
SetTextColor(hdc,RGB(0,255,0));
SetBkColor(hdc,RGB(0,0,0));
SetBkMode(hdc,OPAQUE);

// build up the messages
sprintf(buffer,"The 1 second timer has fired %d times",++counter1);

// print the message
TextOut(hdc,0,0,buffer,strlen(buffer));

// release the dc
ReleaseDC(hwnd,hdc);
}
break;
case TIMER_ID_3SEC:
{
//MessageBox(hwnd,TEXT("timer 3 fired!"),NULL,MB_OK);
// make a beep
MessageBeep(MB_ICONEXCLAMATION);

// get the dc
hdc = GetDC(hwnd);

// set the color
SetTextColor(hdc,RGB(0,255,0));
SetBkColor(hdc,RGB(0,0,0));
SetBkMode(hdc,OPAQUE);

// build up the messages
sprintf(buffer,"The 3 second timer has fired %d times",++counter3);

// print the message
TextOut(hdc,0,20,buffer,strlen(buffer));

// release the dc
ReleaseDC(hwnd,hdc);
}
break;
}
}
break;

case WM_PAINT:
{
// simply validate the window
hdc = BeginPaint(hwnd,&ps);
// you would do all your painting here
//TextOut(hdc,0,0,buffer,strlen(buffer));
EndPaint(hwnd,&ps);

// return success
return(0);
} break;
/* case WM_CLOSE:
{
///display message box
int result = MessageBox(hwnd,TEXT("Close The Window???"),TEXT("Null"),MB_YESNO);
///does the uders want to close ?
if (IDYES == result)
return DefWindowProc(hwnd,msg,wparam,lparam);///call default handler
return 0; /////throw message away
}break;
*/
//////调用顺序：WM_CLOSE---->WM_DESTROY--->WM_QUIT

case WM_DESTROY:
{
// kill the application, this sends a WM_QUIT message

KillTimer(hwnd,TIMER_ID_1SEC);
KillTimer(hwnd,TIMER_ID_3SEC);
PostQuitMessage(0);

// return success
return(0);
} break;

default:break;

} // end switch
// process any messages that we didn't take care of
return (DefWindowProc(hwnd, msg, wparam, lparam));

} // end WinProc


///start game main
void Game_Main()
{



}



// WINMAIN ////////////////////////////////////////////////
int WINAPI WinMain( HINSTANCE hinstance,
HINSTANCE hprevinstance,
LPSTR lpcmdline,
int ncmdshow)
{

WNDCLASSEX winclass; // this will hold the class we create
HWND hwnd; // generic window handle
MSG msg; // generic message

// first fill in the window class stucture
winclass.cbSize = sizeof(WNDCLASSEX);
winclass.style = CS_DBLCLKS | CS_OWNDC |
CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc = WindowProc;
winclass.cbClsExtra = 0;
winclass.cbWndExtra = 0;
winclass.hInstance = hinstance;
winclass.hIcon = LoadIcon(hinstance, IDI_APPLICATION);
winclass.hCursor = LoadCursor(hinstance, IDC_ARROW);
winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName = NULL;
winclass.lpszClassName = WINDOW_CLASS_NAME;
winclass.hIconSm = LoadIcon(hinstance, IDI_APPLICATION);

// register the window class
if (!RegisterClassEx(&winclass))
return(0);

// create the window
if (!(hwnd = CreateWindowEx(NULL, // extended style
WINDOW_CLASS_NAME, // class
"Demo of Custom Cursor and Icon", // title
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
0,0, // initial x,y
400,400,
//GetSystemMetrics(SM_CXFULLSCREEN),
//GetSystemMetrics(SM_CYFULLSCREEN), // initial width, height
NULL, // handle to parent
NULL, // handle to menu
hinstance,// instance of this application
NULL))) // extra creation parms
return(0);

main_window_handle = hwnd;//这里赋的值
main_instance = hinstance;

// enter main event loop, but this time we use PeekMessage()
// instead of GetMessage() to retrieve messages
while(TRUE)
{
// test if there is a message in queue, if so get it
if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
{
// test if this is a quit
if (msg.message == WM_QUIT)
break;

// translate any accelerator keys
TranslateMessage(&msg);

// send the message to the window proc
DispatchMessage(&msg);
} // end if

// main game processing goes here
//Game_Main(); // or whatever your loop is called
if(KEYDOWN(VK_ESCAPE))
SendMessage(hwnd,WM_CLOSE,0,0);////////WM_QUIT为什么不行？？？？

} // end while

// return to Windows like this
return(msg.wParam);

} // end WinMain

///////////////////////////////////////////////////////////

加红色的那个地方请各位解释一下为什么赋值不成功......
谢谢啦.....

[wltg2001]

一个可能是因为系统在发出WM_CREATE时CreateWindowEx函数还没有返回。

[yaoxinchao]

[Quote=引用 1 楼 的回复:]

一个可能是因为系统在发出WM_CREATE时CreateWindowEx函数还没有返回。
[/Quote]

WM_CREATE消息不是在窗口被创建时产生么，没返回哪里来的窗口呢？

[wltg2001]

[Quote=引用 2 楼 的回复:]
引用 1 楼 的回复:

一个可能是因为系统在发出WM_CREATE时CreateWindowEx函数还没有返回。


WM_CREATE消息不是在窗口被创建时产生么，没返回哪里来的窗口呢？
[/Quote]
MSDN上的原话：
The WM_CREATE message is sent when an application requests that a window be created by calling the CreateWindowEx or CreateWindow function. (The message is sent before the function returns.)
也就是说，这个消息是CreateWindow这个API在执行过程中发送的，发送这个消息时CreateWindow这个API并没有执行完，所以当你的程序在处理WM_CREATE时，CreateWindowEx还没有返回，你上面的赋值语句还没有执行到。

[yaoxinchao]

[Quote=引用 3 楼 的回复:]

引用 2 楼 的回复:
引用 1 楼 的回复:

一个可能是因为系统在发出WM_CREATE时CreateWindowEx函数还没有返回。


WM_CREATE消息不是在窗口被创建时产生么，没返回哪里来的窗口呢？

MSDN上的原话：
The WM_CREATE message is sent when an application requests that a wind……
[/Quote]

嗯，谢谢...