1.  1 #include<windows.h>
    2 LRESULT CALLBACK WndProc(
    3 HWND hwnd, // handle to window
    4 UINT uMsg, // message identifier
    5 WPARAM wParam, // first message parameter
    6 LPARAM lParam // second message parameter
    7 );
    8 HINSTANCE hInstanc;
    9 int WINAPI WinMain(HINSTANCE hInstance,
   10 HINSTANCE hPrevInstance,
   11 LPSTR lpCmdLine,
   12 int nShowCmd )
   13 {
   14 WNDCLASS wndclass;
   15 wndclass.style=CS_HREDRAW|CS_VREDRAW;
   16 wndclass.cbClsExtra=0;
   17 wndclass.cbWndExtra=0;
   18 wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
   19 wndclass.hCursor=LoadCursor(NULL,"IDC_ARROW");
   20 wndclass.hIcon=LoadIcon(NULL,"END");
   21 wndclass.hInstance=hInstance;
   22 wndclass.lpfnWndProc=WndProc;
   23 wndclass.lpszClassName="yqh";
   24 wndclass.lpszMenuName=NULL;
   25 RegisterClass(&wndclass);
   26 HWND hWnd;
   27 hWnd=CreateWindow("yqh","xianshichengxu",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,0,CW_USEDEFAULT,0,NULL,NULL,hInstance,NULL);
   28 ShowWindow(hWnd,SW_SHOWNORMAL);
   29 UpdateWindow(hWnd);
   30 MSG message;
   31 while(GetMessage(&message,0,0,0))
   32 {
   33 TranslateMessage(&message);
   34 DispatchMessage(&message);
   35 }
   36 return 0;
   37 }
   38 LRESULT CALLBACK WndProc(
   39 HWND hwnd, // handle to window
   40 UINT uMsg, // message identifier
   41 WPARAM wParam, // first message parameter
   42 LPARAM lParam // second message parameter
   43 )
   44 {
   45 static HWND hwndradio1,hwndradio2,hwndradio3;
   46 static BOOL flag=false;
   47 switch (uMsg)
   48 {
   49 case WM_CREATE:
   50 hwndradio1 = CreateWindow("button","yigeanniu",BS_RADIOBUTTON|WS_CHILD|WS_VISIBLE,10,10,240,25,hwnd,(HMENU)1,hInstanc,NULL);
   51 break;
   52 case WM_COMMAND:
   53 switch (LOWORD(wParam))
   54 {
   55 case 1:
   56 if(flag==false){
   57 SendMessage(hwndradio1,BM_SETCHECK,1,0);
   58 flag=true;}
   59 else if(flag=true)
   60 {
   61 SendMessage(hwndradio1,BM_SETCHECK,0,0);
   62 flag=false;
   63 }
   64 break;
   65 }
   66 break;
   67 //问题在这两行
   68 case WM_PAINT:
   69 break;
   70 case WM_CLOSE:
   71 DestroyWindow(hwnd);
   72 break;
   73 case WM_DESTROY:
   74 PostQuitMessage(0);
   75 break;
   76 default:
   77 return DefWindowProc(hwnd,uMsg,wParam,lParam);
   78 }
   79 return 0;
   80 }

    

67行下面这两行的WM_PAINT消息去掉后运行，直接就会显示按钮，要是有这两行，运行代码后总是要移动一下窗口才会显示，到底为什么？

我查了好多WM_PAINT消息的解释，没怎么看懂，希望各位帮个忙看看。