当我在类范围中声明cpen变量并在ondraw中使用它时MFC应用程序崩溃（...） [英] MFC application is crashing when I declare cpen variable in class scope and using it in ondraw(...)

问题描述

大家好，我正在尝试在类范围内声明一个CPen对象并在OnDraw（...）中使用它。但是当我运行它时我的应用程序崩溃。如果我在OnDraw中声明对象（... ）它工作正常。任何人都可以让我知道如果在类范围内声明CPen对象，我还需要任何额外的东西吗？在此先感谢。



我尝试过：

Hi All, I'm trying to declare a CPen object in class scope and using it in OnDraw(...).But my application is crashing when I run it.If I declare the object in OnDraw(...) it is working fine. Can anyone please let me know do I need to any extra thing if declare CPen object in class scope? Thanks in advance.

What I have tried:

xxxxx.h
private:
  CPen cPen;


xxxxx.cpp

void CMFCApplication2View::OnDraw(CDC* pDC)
{
        //CPen cPen;  If I do it here its working fine.
	CPen* pOldPen = NULL;

	BOOL bCPen = cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));

	
	if (bCPen)
	{
		pOldPen = pDC->SelectObject(&cPen);

		pDC->MoveTo(95, 125);
		pDC->LineTo(230, 125);

		pDC->SelectObject(pOldPen);
		//cPen.DeleteObject();
	}
}

推荐答案

您在每张图纸上一次又一次地调用 CreatePen 。 />


最简单的解决方案是在类的构造函数中调用 CreatePen 并将其从draw函数中删除：

You are calling CreatePen again and again with each drawing.

The simplest solution would be calling CreatePen in the constructor of your class and remove it from the draw function:

CMFCApplication2View::CMFCApplication2View()
{
    // Other initialisation goes here

    cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));
}

void CMFCApplication2View::OnDraw(CDC* pDC)
{
    CPen* pOldPen = pDC->SelectObject(&cPen);

    // Perform drawing here

    pDC->SelectObject(pOldPen);
}

BOOL CPen = cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));

这个陈述到底是什么意思？您正在将类名称（ CPen ）重新声明为 BOOL ean变量。

What on earth is that statement supposed to be? You are redeclaring a class name (CPen) as a BOOLean variable.

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