自然界面里，各种生物都是有其生命周期的。程序也是有其生命周期的，创建时就是它出生了，当它运行工作中就是成年期，最后少不了要死亡的，那么程序的死亡是怎么样出现的呢？像以前介绍函数GetMessage里是使用一个循环不断地检测消息，周止复始的，是不可能出现死亡的，但它会检测到消息WM_QUIT就退出来。那现在问题是谁发送WM_QUIT消息出来呢？这就是PostQuitMessage函数所做的工作。当你点击窗口右上角的关闭时，Windows就会把窗口从系统里删除，这时就会发出消息WM_DESTROY给窗口消息处理函数WindowProc，WindowProc收到这条消息后，最需要做的一件事情就是调用PostQuitMessage发出退出消息，让消息循环结束。
函数PostQuitMessage声明如下：
WINUSERAPI
VOID
WINAPI
PostQuitMessage(
__in int nExitCode);
nExitCode是退出标识码，它被放到WM_QUIT消息的参数wParam里。
调用这个几个函数的例子如下：
#include "stdafx.h"
#include "resource.h"
#define MAX_LOADSTRING 255
HINSTANCE hinst;
TCHAR szClass[MAX_LOADSTRING];
TCHAR szTitle[MAX_LOADSTRING];
ATOM MyRegisterClass(HINSTANCE hInstance);
LRESULT CALLBACK MyProc(HWND, UINT, WPARAM, LPARAM);
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow);
int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
MSG msg;
HACCEL hAccelTab;
LoadString(hInstance, IDS_SZCLASS, szClass, MAX_LOADSTRING); //加载资源里的字符串
LoadString(hInstance, IDS_SZTITLE, szTitle, MAX_LOADSTRING); //加载资源里的字符串
MyRegisterClass(hInstance);
if(!InitInstance(hInstance, SW_SHOWNORMAL))
{
return FALSE;
}
hAccelTab = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTWIN));
while (GetMessage(&msg, NULL, 0, 0)) //获取所有窗口的消息
{
TranslateMessage(&msg); //调用函数TranslateMessage作消息转换工作
DispatchMessage(&msg); //调用函数DispatchMessage发送消息
}
return msg.wParam;
}
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hinst = hInstance;
HWND hwnd;
hwnd = CreateWindow(szClass, szTitle , WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, NULL, NULL, hInstance, NULL);
if (!hwnd)
{
return FALSE;
}
ShowWindow(hwnd, nCmdShow);
UpdateWindow(hwnd);
return TRUE;
}
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = MyProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(NULL, MAKEINTRESOURCE(IDI_MAIN));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wcex.lpszMenuName = MAKEINTRESOURCE(IDR_MAIN);
wcex.lpszClassName = szClass;
wcex.hIconSm = NULL;
return RegisterClassEx(&wcex);
}
LRESULT CALLBACK MyProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hdc;
switch(uMsg)
{
case WM_COMMAND:
switch(LOWORD(wParam))
{
case IDM_ABOUT:
DialogBox(hinst, MAKEINTRESOURCE(IDD_ABOUT), hwnd, NULL);
break;
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0); //调用函数PostQuitMessage来处理退出应用程序
break;
case WM_PAINT:
hdc = BeginPaint(hwnd,&ps);
EndPaint(hwnd,&ps);
break;
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
}
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