一个简单的画直线类出现的问题

Question

小弟刚VC不久,遇到的问题真不少.下面就是一个画直线的类出的问题.
我定义了一个直线类.
DrawLine.h的代码:#if !defined(AFX_DRAWLINE_H__1C5A6622_9C9C_448D_A1F2_5A205B666E31__INCLUDED_)
#define AFX_DRAWLINE_H__1C5A6622_9C9C_448D_A1F2_5A205B666E31__INCLUDED_#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000class CDrawLine  
{public:
CDrawLine();
virtual ~CDrawLine();
public:
bool sign;
CDC* pDC;
int type;
void OnLButtonDown(UINT nFlags,CPoint Point);
void OnLButtonUp(UINT nFlags,CPoint Point);
void OnMouseMove(UINT nFlags,CPoint Point);
void OnRButtonDown(UINT nFlags,CPoint Point);};#endif // !defined(AFX_DRAWLINE_H__1C5A6622_9C9C_448D_A1F2_5A205B666E31__INCLUDED_)
下面是DrawLine.cpp里面的代码:#include "stdafx.h"
#include "VCCAD.h"
#include "DrawLine.h"#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////
extern CView *pView;//我付给了它当前的视类的指针
CDrawLine::CDrawLine()
{
type=1;
sign=0;
pDC=pView->GetDC();}CDrawLine::~CDrawLine()
{}
void  CDrawLine::OnLButtonDown(UINT nFlags,CPoint Point)
{
sign=1;
pDC->LineTo(Point);
}
void CDrawLine::OnLButtonUp(UINT nFlags,CPoint Point)
{
sign=0;
}
void CDrawLine::OnMouseMove(UINT nFlags,CPoint Point)
{   
if(sign==1)
pDC->MoveTo(Point);}void CDrawLine::OnRButtonDown(UINT nFlags,CPoint Point)
{
sign=0;
}
我还没有定义它的对象,编译的时候可以通过,但是不能执行,不知道为什么,请大家给点意见.

Answer 1

OnMouseMove
这个事件中用LineToOnLButtonDown
这个事件中用MoveTo

Answer 2

回wanilyer(缘随影去)
还是不行啊,我刚改了,也试了,就是不行,你看是不是别的原因,谢谢.

Answer 3

你的CDrawLine类对象是CView的成员吧，那她构造的时候pView是否是啥状况，没见你给pView赋值啊，不知道你在那儿的extern啥意图，在pDC=pView->GetDC();这句加个断点监视一下看看pView吧，还有，自己写类没必要起名OnLButtonDown吧，扎一看还以为是CView个人观点

Answer 4

对了，extern CView *pView的意思图就是要取得当前的视类的指针，然后好在视类窗口上画图，我这样想是不是有问题？？这只是简单的一个类，按照这个思想我还可以设计其它的作图类，不过好像有问题。

Answer 5

老大！你有没搞错啊！首先你的流程就不对，更别提实现你的效果了！画直线 首先要在你的类里申明一个成员变量，OnLButtonDown记录画直线的起始坐标；
再在OnLButtonUp中 moveto（成员变量） ，lineto（Point）

Answer 6

我也是刚学vc++，今后多探讨探讨。
下面是我写的一个画带箭头直线的代码，给你看看：// DrawMainView.cpp : implementation of the CDrawMainView class
//#include "stdafx.h"
#include "DrawMain.h"#include "DrawMainDoc.h"
#include "DrawMainView.h"
#include <MATH.H>
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endifconst double PI=3.1415926;
const int ArrDgr=30;
const int LineLen=30;
/////////////////////////////////////////////////////////////////////////////
// CDrawMainViewIMPLEMENT_DYNCREATE(CDrawMainView, CView)BEGIN_MESSAGE_MAP(CDrawMainView, CView)
//{{AFX_MSG_MAP(CDrawMainView)
ON_WM_CREATE()
ON_WM_LBUTTONDOWN()
ON_WM_LBUTTONUP()
ON_WM_MOUSEMOVE()
ON_WM_RBUTTONDOWN()
//}}AFX_MSG_MAP
// Standard printing commands
ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CDrawMainView construction/destructionCDrawMainView::CDrawMainView()
{
// TODO: add construction code here
BSign=FALSE;
}CDrawMainView::~CDrawMainView()
{
}BOOL CDrawMainView::PreCreateWindow(CREATESTRUCT& cs)
{
// TODO: Modify the Window class or styles here by modifying
//  the CREATESTRUCT cs return CView::PreCreateWindow(cs);
}/////////////////////////////////////////////////////////////////////////////
// CDrawMainView drawingvoid CDrawMainView::OnDraw(CDC* pDC)
{
CDrawMainDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
// TODO: add draw code for native data here
}/////////////////////////////////////////////////////////////////////////////
// CDrawMainView printingBOOL CDrawMainView::OnPreparePrinting(CPrintInfo* pInfo)
{
// default preparation
return DoPreparePrinting(pInfo);
}void CDrawMainView::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
// TODO: add extra initialization before printing
}void CDrawMainView::OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
// TODO: add cleanup after printing
}/////////////////////////////////////////////////////////////////////////////
// CDrawMainView diagnostics#ifdef _DEBUG
void CDrawMainView::AssertValid() const
{
CView::AssertValid();
}void CDrawMainView::Dump(CDumpContext& dc) const
{
CView::Dump(dc);
}CDrawMainDoc* CDrawMainView::GetDocument() // non-debug version is inline
{
ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CDrawMainDoc)));
return (CDrawMainDoc*)m_pDocument;
}
#endif //_DEBUG/////////////////////////////////////////////////////////////////////////////
// CDrawMainView message handlersint CDrawMainView::OnCreate(LPCREATESTRUCT lpCreateStruct) 
{
if (CView::OnCreate(lpCreateStruct) == -1)
return -1;
// TODO: Add your specialized creation code here
m_OrgPot.x=0;
m_OrgPot.y=0;
return 0;
}
 void CDrawMainView::OnLButtonDown(UINT nFlags, CPoint point) 
{
// TODO: Add your message handler code here and/or call default
    m_OrgPot=point;
m_OldPot=point;
BSign=TRUE;
CView::OnLButtonDown(nFlags, point);
}

Answer 7

////续上void CDrawMainView::OnLButtonUp(UINT nFlags, CPoint point) 
{
// TODO: Add your message handler code here and/or call default
/*CDC *dc;
dc=GetDC();
dc->MoveTo(m_OrgPot);
    dc->LineTo(point);
ReleaseDC(dc);*/
//CClientDC dc(this);
//dc.MoveTo(m_OrgPot);
//dc.LineTo(point);
BSign=FALSE;
CView::OnLButtonUp(nFlags, point);
}void CDrawMainView::OnMouseMove(UINT nFlags, CPoint point) 
{
// TODO: Add your message handler code here and/or call default
if (BSign) 
{
CClientDC dc(this);  
dc.SetROP2(R2_NOTXORPEN);
CPen pen(PS_SOLID,4,RGB(0,255,0)); 
dc.SelectObject(&pen); 
dc.MoveTo(m_OrgPot);
dc.LineTo(m_OldPot);
double x,y,degree;
CPoint ptL,ptR; 
if (m_OrgPot.x<=m_OldPot.x)
{
if (m_OrgPot.y<=m_OldPot.y)
{ 
x=double(m_OldPot.x-m_OrgPot.x);
y=double(m_OldPot.y-m_OrgPot.y);
degree=atan(y/x)+(ArrDgr*PI/180); 
ptR.x=m_OldPot.x-int(LineLen*cos(degree)+0.5);
ptR.y=m_OldPot.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptR);
degree=atan(y/x)-(ArrDgr*PI/180);
ptL.x=m_OldPot.x-int(LineLen*cos(degree)+0.5);
ptL.y=m_OldPot.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptL);
}
else
{
x=double(m_OldPot.x-m_OrgPot.x);
y=double(m_OrgPot.y-m_OldPot.y);
degree=atan(y/x)+(ArrDgr*PI/180); 
ptR.x=m_OldPot.x-int(LineLen*cos(degree)+0.5);
ptR.y=m_OldPot.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptR);
degree=atan(y/x)-(ArrDgr*PI/180);
ptL.x=m_OldPot.x-int(LineLen*cos(degree)+0.5);
ptL.y=m_OldPot.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptL);
}
}
else
{
if (m_OrgPot.y<=m_OldPot.y)
{
x=double(m_OrgPot.x-m_OldPot.x);
y=double(m_OldPot.y-m_OrgPot.y);
degree=atan(y/x)-(ArrDgr*PI/180); 
ptR.x=m_OldPot.x+int(LineLen*cos(degree)+0.5);
ptR.y=m_OldPot.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptR);
degree=atan(y/x)+(ArrDgr*PI/180);
ptL.x=m_OldPot.x+int(LineLen*cos(degree)+0.5);
ptL.y=m_OldPot.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptL);
}
else
{
x=double(m_OrgPot.x-m_OldPot.x);
y=double(m_OrgPot.y-m_OldPot.y);
degree=atan(y/x)-(ArrDgr*PI/180); 
ptR.x=m_OldPot.x+int(LineLen*cos(degree)+0.5);
ptR.y=m_OldPot.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptR);
degree=atan(y/x)+(ArrDgr*PI/180);
ptL.x=m_OldPot.x+int(LineLen*cos(degree)+0.5);
ptL.y=m_OldPot.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(m_OldPot);
dc.LineTo(ptL);
}
}  
dc.MoveTo(m_OrgPot);
dc.LineTo(point); 
if (m_OrgPot.x<=point.x)
{
if (m_OrgPot.y<=point.y)
{
x=double(point.x-m_OrgPot.x);
y=double(point.y-m_OrgPot.y);
degree=atan(y/x)+(ArrDgr*PI/180); 
ptR.x=point.x-int(LineLen*cos(degree)+0.5);
ptR.y=point.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptR);
degree=atan(y/x)-(ArrDgr*PI/180);
ptL.x=point.x-int(LineLen*cos(degree)+0.5);
ptL.y=point.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptL);

}
else
{
x=double(point.x-m_OrgPot.x);
y=double(m_OrgPot.y-point.y);
degree=(ArrDgr*PI/180)+atan(y/x);
ptR.x=point.x-int(LineLen*cos(degree)+0.5);
ptR.y=point.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptR); 
degree=atan(y/x)-(ArrDgr*PI/180); 
ptL.x=point.x-int(LineLen*cos(degree)+0.5);
ptL.y=point.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptL);
}
}
else
{
if (m_OrgPot.y<=point.y)
{
x=double(m_OrgPot.x-point.x);
y=double(point.y-m_OrgPot.y);
degree=atan(y/x)-(ArrDgr*PI/180); 
ptR.x=point.x+int(LineLen*cos(degree)+0.5);
ptR.y=point.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptR);
degree=atan(y/x)+(ArrDgr*PI/180);
ptL.x=point.x+int(LineLen*cos(degree)+0.5);
ptL.y=point.y-int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptL);
}
else
{
x=double(m_OrgPot.x-point.x);
y=double(m_OrgPot.y-point.y);
degree=atan(y/x)-(ArrDgr*PI/180); 
ptR.x=point.x+int(LineLen*cos(degree)+0.5);
ptR.y=point.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptR);
degree=atan(y/x)+(ArrDgr*PI/180);
ptL.x=point.x+int(LineLen*cos(degree)+0.5);
ptL.y=point.y+int(LineLen*sin(degree)+0.5);
dc.MoveTo(point);
dc.LineTo(ptL);
}
}
m_OldPot=point;
}
CView::OnMouseMove(nFlags, point);
}void CDrawMainView::OnRButtonDown(UINT nFlags, CPoint point) 
{
// TODO: Add your message handler code here and/or call default
  }