Question

VC++ 窗口重绘

上次问那些太乱了，说简单一点是这样的：
书上说建WIN32 APPLICATION工程，并将WINDOWS应用程序的类型设置为:A TYPICAL "HELLO WORLD!" APPLICATION.
添加资源后在WndProc()中对WM_PAINT消息处理：
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
// TODO: 在此添加任意绘图代码...
HBITMAP hbmp;
HDC srchdc;
hbmp=LoadBitmap(hInst,(LPCTSTR)IDB_BITMAP1);
srchdc=CreateCompatibleDC(hdc);
SelectObject(srchdc,hbmp);
BitBlt(hdc,100,100,500,500,srchdc,0,0,SRCCOPY);
DeleteObject(hbmp);
DeleteObject(srchdc);
EndPaint(hWnd, &ps);
break;
这是完全照书写的，没问题。
可是把这几句移到WndProc()的开始为什么就不行了，变量定义为全局，写成这样：
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
hdc=GetDC(hWnd);
HBITMAP hbmp;
HDC srchdc;
hbmp=LoadBitmap(hInst,(LPCTSTR)IDB_BITMAP1);
switch (message)
{
case WM_PAINT:
srchdc=CreateCompatibleDC(hdc);
SelectObject(srchdc,hbmp);
BitBlt(hdc,100,100,500,500,srchdc,0,0,SRCCOPY);
DeleteObject(hbmp);
DeleteObject(srchdc);
EndPaint(hWnd, &ps);
break;

Answer 1

WndProc是在每次有窗口消息后由系统调用的，
把它放到前面则一由消息，不管是WM_PAINT还是一般的键盘，鼠标等等消息都在loadBitmap,如果非要先loadbitmap,在WM_Create中添加(只运行一次),在需要在不需要的时候释放