问题描述
- windows程序设计 为什么窗口一开始空白，需要最小化或者改变大小才显示
- /*-----------------------------------------
SINEWAVE.C -- Sine Wave Using Polyline
(c) Charles Petzold 1998
-----------------------------------------*/#include
#include#define NUM 1000
#define TWOPI (2 * 3.14159)LRESULT CALLBACK WndProc(HWND UINT WPARAM LPARAM);
int WINAPI WinMain(HINSTANCE hInstance HINSTANCE hPrevInstance
PSTR szCmdLine int iCmdShow)
{
static TCHAR szAppName[] = TEXT(""SineWave"");
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;}hwnd = CreateWindow(szAppName TEXT(""Sine Wave Using Polyline"") 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 int cxClient cyClient;
HDC hdc;
int i;
PAINTSTRUCT ps;
POINT apt[NUM];switch (message){case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); return 0;case WM_PAINT: hdc = BeginPaint(hwnd &ps); MoveToEx(hdc 0 cyClient / 2 NULL); LineTo(hdc cxClient cyClient / 2); for (i = 0; i < NUM; i++) { apt[i].x = i * cxClient / NUM; apt[i].y = (int)(cyClient / 2 * (1 - sin(TWOPI * i / NUM))); } Polyline(hdc apt NUM); return 0;case WM_DESTROY: PostQuitMessage(0); return 0;}return DefWindowProc(hwnd message wParam lParam);}
而一般的程序都是直接显示，这个程序哪儿不同了？
下面是前面写过的一个。
#include
#include""SYSMETS.h""
LRESULT CALLBACK WndProc(HWND UINT WPARAM LPARAM);int WINAPI WinMain(HINSTANCE hInstance HINSTANCE hPrevInstance PSTR szCmdLine int iCmdShow)
{
static WCHAR szAppName[] = L""SYSMET1"";
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(nullptr IDI_APPLICATION);wndclass.hCursor = LoadCursor(nullptr IDC_ARROW);wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);wndclass.lpszMenuName = nullptr;wndclass.lpszClassName = szAppName;if (!RegisterClass(&wndclass)){ MessageBox(NULL L""需要win32操作系统。"" L""error"" MB_OKCANCEL); return 0;}hwnd = CreateWindow(szAppName L""SYSMETS"" WS_OVERLAPPEDWINDOW|WS_VSCROLL CW_USEDEFAULT CW_USEDEFAULT CW_USEDEFAULT CW_USEDEFAULT nullptr nullptr hInstance nullptr);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 int cxChar cyChar cxCapscyClientiVscrollPos;
HDC hdc;
PAINTSTRUCT ps;
TEXTMETRIC tm;
static wchar_t szBuffer[10];
switch (message)
{
case WM_CREATE:
hdc = GetDC(hwnd);
GetTextMetrics(hdc &tm);
cxChar = tm.tmAveCharWidth;
cyChar = tm.tmHeight + tm.tmExternalLeading;
cxCaps = int(1.5*double(cxChar));
ReleaseDC(hwnd hdc);SetScrollRange(hwnd SB_VERT 0 NUMLINES - 1 FALSE); SetScrollPos(hwndSB_VERTiVscrollPosTRUE); return 0;case WM_SIZE: cyClient = HIWORD(lParam); return 0;case WM_VSCROLL: switch (LOWORD(wParam)) { case SB_LINEUP: iVscrollPos -= 1;break; break; case SB_LINEDOWN: iVscrollPos += 1;break; case SB_PAGEUP: iVscrollPos -= cyClient / cyChar;break; case SB_PAGEDOWN: iVscrollPos += cyClient / cyChar;break; case SB_THUMBPOSITION: iVscrollPos = HIWORD(wParam);break; default:break; } if (iVscrollPos < 0)iVscrollPos = 0; else if (iVscrollPos>NUMLINES - 1)iVscrollPos = NUMLINES - 1; if (iVscrollPos != GetScrollPos(hwnd SB_VERT)) { SetScrollPos(hwnd SB_VERT iVscrollPos TRUE); InvalidateRect(hwnd NULL TRUE); }case WM_PAINT: hdc = BeginPaint(hwnd &ps); for (int i = 0;i != NUMLINES;++i) { int y = cyChar*(i - iVscrollPos); TextOut(hdc 0 y sysmetrics[i].szLabel lstrlen(sysmetrics[i].szLabel)); TextOut(hdc 22 * cxCaps y sysmetrics[i].szDesc lstrlen(sysmetrics[i].szDesc)); SetTextAlign(hdc TA_RIGHT | TA_TOP); TextOut(hdc 22 * cxCaps + 40 * cxChar y szBuffer wsprintf(szBuffer L""%5d"" GetSystemMetrics(sysmetrics[i].iIndex))); SetTextAlign(hdc TA_LEFT | TA_TOP); } EndPaint(hwnd &ps); return 0;case WM_DESTROY: PostQuitMessage(0); return 0;}return DefWindowProc(hwnd message wParam lParam);}
具体什么原因 求大神解答，自己从WM_SIZE WM_CREATE UpdateWindow各个方面去思考都想不通。
解决方案
本人感觉应该是没有刷新窗口的原因，在最小化然后最大化之后窗口重新刷新了，所以这个时候才显示了。