windows程序设计画线问题 在线等

Question

代码没发现错误.不过你画线之前,应该先创建画笔(CreatePen),并选入HDC(SelectObject)

Answer 1

#include<windows.h>
#include<stdio.h>LRESULT CALLBACK MyWindowProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);
int WINAPI WinMain(
  HINSTANCE hInstance,      // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,          // command line
  int nCmdShow              // show state
)
{
MSG msg;
static TCHAR szClassName[]=TEXT("Hello Windows");
HWND hwnd;
    WNDCLASS wndclass;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hbrBackground=(HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.hCursor=LoadCursor(NULL,IDC_CROSS);
wndclass.hIcon=LoadIcon(NULL,IDI_WARNING);
    wndclass.hInstance=hInstance;
wndclass.lpfnWndProc=MyWindowProc;
wndclass.lpszClassName=szClassName;
wndclass.lpszMenuName=0;
wndclass.style=CS_HREDRAW | CS_VREDRAW;

RegisterClass(&wndclass); hwnd=CreateWindow(szClassName,"WoQu",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT,
CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,hInstance,NULL); ShowWindow(hwnd,SW_SHOWNORMAL); UpdateWindow(hwnd); while(GetMessage(&msg,NULL,NULL,NULL))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}LRESULT CALLBACK MyWindowProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
)
{
PAINTSTRUCT ps;
switch(uMsg)
{
case WM_PAINT:
HDC hdc;
hdc=BeginPaint(hwnd,&ps);
MoveToEx(hdc,100,120,NULL);
LineTo(hdc,200,250);
EndPaint(hwnd,&ps);
break;

default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;}

Answer 2

修改这样试一下，把HDC定义在前面，不能在CASE里面定义变量，或者用{}包含也可以：
HDC hdc;
switch(uMsg)
{
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
MoveToEx(hdc,100,120,NULL);
LineTo(hdc,200,250);
EndPaint(hwnd,&ps);
break;default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
另外严谨的做法应该是建立画笔，因为默认的画笔可以与底色一样，也可能看不到线，这样不好定位错误

Answer 3

改过之后还是运行不了啊  在我的另外一个程序是可以的
到底是什么情况啊
代码如下
#include<windows.h>
#include<stdio.h>LRESULT CALLBACK MyWindowProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);
int WINAPI WinMain(
  HINSTANCE hInstance,      // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,          // command line
  int nCmdShow              // show state
)
{
MSG msg;
static TCHAR szClassName[]=TEXT("Hello Windows");
HWND hwnd;
    WNDCLASS wndclass;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hbrBackground=(HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.hCursor=LoadCursor(NULL,IDC_CROSS);
wndclass.hIcon=LoadIcon(NULL,IDI_WARNING);
    wndclass.hInstance=hInstance;
wndclass.lpfnWndProc=MyWindowProc;
wndclass.lpszClassName=szClassName;
wndclass.lpszMenuName=0;
wndclass.style=CS_HREDRAW | CS_VREDRAW;

RegisterClass(&wndclass); hwnd=CreateWindow(szClassName,"WoQu",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT,
CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,hInstance,NULL); ShowWindow(hwnd,SW_SHOWNORMAL); UpdateWindow(hwnd); while(GetMessage(&msg,NULL,NULL,NULL))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}LRESULT CALLBACK MyWindowProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
)
{
static bool PLAYSND=FALSE;
static int TEXTPOS=50;
HDC hdc;
PAINTSTRUCT ps;
RECT rect; switch(uMsg)
{
// case WM_CREATE:
// PlaySound ("LemonTree.wav", NULL, SND_FILENAME | SND_ASYNC ) ;
// break; case WM_PAINT:
TEXTPOS=50;
hdc=BeginPaint(hwnd,&ps);
TextOut(hdc,0,0,"窗口你好",strlen("窗口你好"));
GetClientRect(hwnd,&rect);
if(TRUE==PLAYSND)
DrawText(hdc,"正在播放音乐Lemon Tree",-1,&rect,DT_SINGLELINE | DT_CENTER | DT_VCENTER);
// TextOut(hdc,450,230,"正在播放音乐Lemon Tree",strlen("正在播放音乐Lemon Tree"));
else
DrawText(hdc,"按空格键播放音乐",-1,&rect,DT_SINGLELINE | DT_CENTER | DT_VCENTER);
// TextOut(hdc,450,230 ,"按空格键播放音乐",strlen("按空格键播放音乐")); MoveToEx(hdc,100,120,NULL);  //画线
                   LineTo(hdc,200,250); EndPaint(hwnd,&ps);
break;
        
case WM_CHAR:
if(('q'==wParam) | ('Q'==wParam))
DestroyWindow(hwnd);
else 
if(' '==wParam)
{
PlaySound ("LemonTree.wav", NULL, SND_FILENAME | SND_ASYNC ) ;
PLAYSND=TRUE;
InvalidateRect(NULL,NULL,TRUE);
}
else
MessageBox(hwnd,"按Q键也能退出","提示",MB_OK);
break; case WM_LBUTTONDOWN:
MessageBox(hwnd,"这是鼠标左键","NOTICE",MB_OK);/* HDC hDc;
     int iWidth;
hDc=GetDC(hwnd);
iWidth=GetDeviceCaps(hDc,HORZRES);      //iWidth=1366
ReleaseDC(hwnd,hDc);
*/
break; case WM_RBUTTONDOWN:
HDC hDC;
hDC=GetDC(hwnd);
TextOut(hDC,0,TEXTPOS,"点右键干嘛",strlen("点右键干嘛"));
TEXTPOS+=20;
ReleaseDC(hwnd,hDC);
break; case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"确定关闭吗","提示",MB_YESNO))
DestroyWindow(hwnd);
break; case WM_DESTROY:
PostQuitMessage(0);
break; default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;
}

Answer 4

#include<windows.h>
#include<stdio.h>LRESULT CALLBACK MyWindowProc( HWND hwnd, // handle to window
                               UINT uMsg, // message identifier
                               WPARAM wParam, // first message parameter
                               LPARAM lParam // second message parameter );
int WINAPI WinMain( HINSTANCE hInstance, // handle to current instance
                    HINSTANCE hPrevInstance, // handle to previous instance
                    LPSTR lpCmdLine, // command line
                    int nCmdShow // show state )
{
     MSG msg;
     static TCHAR szClassName[]=TEXT("Hello Windows");
     HWND hwnd;
     WNDCLASS wndclass;
     wndclass.cbClsExtra=0;
     wndclass.cbWndExtra=0;
     wndclass.hbrBackground=(HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.hCursor=LoadCursor(NULL,IDC_CROSS);
     wndclass.hIcon=LoadIcon(NULL,IDI_WARNING);
     wndclass.hInstance=hInstance;
     wndclass.lpfnWndProc=MyWindowProc;
     wndclass.lpszClassName=szClassName;
     wndclass.lpszMenuName=0;
     wndclass.style=CS_HREDRAW | CS_VREDRAW;     RegisterClass(&wndclass);

     hwnd=CreateWindow(szClassName,"WoQu",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT,
                   CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,hInstance,NULL);

     ShowWindow(hwnd,SW_SHOWNORMAL);

     UpdateWindow(hwnd);

     while(GetMessage(&msg,NULL,NULL,NULL))
     {
          TranslateMessage(&msg);
          DispatchMessage(&msg);
      }
      return 0;}LRESULT CALLBACK MyWindowProc( HWND hwnd, // handle to window
                               UINT uMsg, // message identifier
                               WPARAM wParam, // first message parameter
                               LPARAM lParam // second message parameter)
{
     PAINTSTRUCT ps;
     HDC hdc; // 在这里定义设备属性表(Device Contex)句柄
     switch(uMsg)
     {
      case WM_PAINT:
           hdc=BeginPaint(hwnd,&ps);
           MoveToEx(hdc,100,120,NULL);
           LineTo(hdc,200,250);
           EndPaint(hwnd,&ps);
           break;

      default:
           return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
      return 0;
}

Answer 5

你的画线代码放在WM_PAINT消息里不合适，因为没有触发WM_PAINT消息，可以放在WM_CREAT里面