这个VC绘图函数错在哪？

[烤火的鱼]

我编写了一个小程序，其中有一段代码是模拟按钮，经简化后如下：

//模拟按钮
void uButton(CDC *pDC,CRect rect)
{
CPen *pNewPen,*pOldPen;

CBrush *pNewBrush=new CBrush;
pNewBrush->CreateSolidBrush(RGB(192,192,192));
pDC->FillRect(rect,pNewBrush);
delete pNewBrush;

pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(255,255,255));
pOldPen=pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.right-1,rect.top);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.left,rect.bottom-1);
delete pNewPen;

//以下代码与上面相同，只是颜色和坐标变了
pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(0,0,0));
pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.right,rect.top);
pDC->LineTo(rect.right,rect.bottom);
pDC->MoveTo(rect.left,rect.bottom);
pDC->LineTo(rect.right,rect.bottom);
delete pNewPen;

pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(128,128,128));
pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.right-1,rect.top+1);
pDC->LineTo(rect.right-1,rect.bottom-1);
pDC->MoveTo(rect.left+1,rect.bottom-1);
pDC->LineTo(rect.right-1,rect.bottom-1);
delete pNewPen;
pDC->SelectObject(pOldPen);
}

为了测试，我在OnKeyDown()事件中写了如下代码：
{

CDC *pDC=GetDC();
CRect rect;

rect.left=0;
rect.right=100;
rect.top=0;
rect.bottom=70;
uButton(pDC,rect);
//ReleaseDC(pDC);
}

如果你大量调用uButton()函数，如按住回车键不动，过一会儿，图案就变了，再过一会儿就死机了，我实在不知程序错在哪儿，望各为大虾吝指教。

[kxy]

When you no longer need the pen, call the DeleteObject function to delete it.
CreatePen本身创建了一个对象实例，new也创建了
你只释放了一个：）
欢迎去www.midatech.com/kxy下载ChatFtp我一般都在使用这个聊天.

[netmare]

An application should not delete a pen when the pen is selected in a device context,and u should release dc every time,so fix the program like this:

void uButton(CDC *pDC,CRect rect)
{
CPen *pNewPen,*pOldPen;

CBrush *pNewBrush=new CBrush;
pNewBrush->CreateSolidBrush(RGB(192,192,192));
pDC->FillRect(rect,pNewBrush);
delete pNewBrush;

pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(255,255,255));
pOldPen=pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.right-1,rect.top);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.left,rect.bottom-1);
pDC->SelectObject(pOldPen);
delete pNewPen;

//以下代码与上面相同，只是颜色和坐标变了
pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(0,0,0));
pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.right,rect.top);
pDC->LineTo(rect.right,rect.bottom);
pDC->MoveTo(rect.left,rect.bottom);
pDC->LineTo(rect.right,rect.bottom);
pDC->SelectObject(pOldPen);
delete pNewPen;

pNewPen=new CPen;
pNewPen->CreatePen(PS_SOLID,1,RGB(128,128,128));
pDC->SelectObject(pNewPen);
pDC->MoveTo(rect.right-1,rect.top+1);
pDC->LineTo(rect.right-1,rect.bottom-1);
pDC->MoveTo(rect.left+1,rect.bottom-1);
pDC->LineTo(rect.right-1,rect.bottom-1);
pDC->SelectObject(pOldPen);
delete pNewPen;
//pDC->SelectObject(pOldPen);
}

为了测试，我在OnKeyDown()事件中写了如下代码：
{

CDC *pDC=GetDC();
CRect rect;

rect.left=0;
rect.right=100;
rect.top=0;
rect.bottom=70;
uButton(pDC,rect);
ReleaseDC(pDC);
}

[bclzi]

first a pointer
then new an object space
last creat the object

[geofee]

用pointer多见外！
CPen pen(...);
// use pen code
CPen *o = SelectObject(&pen)
// Draw code
SelectObject(o) // Important!!!

pen.DeleteObject(); // for use again!
pen.CreatePen(...)
// use pen code
o = SelectObject(&pen)
// Draw code
SelectObject(o) // Important!!!

// again and again!!

[LJN]

看看以下两行有什么不同,就能解决了。

pOldPen=pDC->SelectObject(pNewPen);
pOldPen=pDC->SelectObject(&pNewPen);

[xingxian]

kxy is a new comer,but pretend to be a expert.haha!

[ad]

netware做得很对， LJN在瞎说。
不过，netware的代码还可作如下优化：

void uButton(CDC *pDC,CRect rect)
{
CPen *pNewPen[3],*pOldPen;

CBrush *pNewBrush=new CBrush;
pNewBrush->CreateSolidBrush(RGB(192,192,192));
pDC->FillRect(rect,pNewBrush);
delete pNewBrush;

pNewPen[0]=new CPen;
pNewPen[0]->CreatePen(PS_SOLID,1,RGB(255,255,255));
pOldPen=pDC->SelectObject(pNewPen[0]);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.right-1,rect.top);
pDC->MoveTo(rect.left,rect.top );
pDC->LineTo(rect.left,rect.bottom-1);

//以下代码与上面相同，只是颜色和坐标变了
pNewPen[1]=new CPen;
pNewPen[1]->CreatePen(PS_SOLID,1,RGB(0,0,0));
pDC->SelectObject(pNewPen[1]);
pDC->MoveTo(rect.right,rect.top);
pDC->LineTo(rect.right,rect.bottom);
pDC->MoveTo(rect.left,rect.bottom);
pDC->LineTo(rect.right,rect.bottom);

pNewPen[2]=new CPen;
pNewPen[2]->CreatePen(PS_SOLID,1,RGB(128,128,128));
pDC->SelectObject(pNewPen[2]);
pDC->MoveTo(rect.right-1,rect.top+1);
pDC->LineTo(rect.right-1,rect.bottom-1);
pDC->MoveTo(rect.left+1,rect.bottom-1);
pDC->LineTo(rect.right-1,rect.bottom-1);

pDC->SelectObject(pOldPen);
for(int i=0;i<3;i++) delete pNewPen[i];
}

还可以进一步优化，既然几段代码都差不多，可以集中到一个循环里做，使源码大大减少（执行效率未必提高）。

[kxy]

我前面的帖子错了,sorry

[zdg]

ad的方法是对的, 操作pen尤其要注意释放...
我建议安装Bounds Checker, 这种Error很容易查出...

[zdg]

http://www.midatech.com/csdn/tools/

[gege]

何处可下载Bounds Checker？