vc++中，mfc在基于对话框的onpaint中画图

[susuding]

初学mfc,如何在基于对话框的onpaint（）类中画图并显示呢，对内部机制不熟，请高手指点。下面是根据网上的和自己的要求写的，但运行存在问题，目的是画一个大圆，并在其中画一个小圆，小圆填充颜色。我的文件名是onpaint
void ConpaintDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // 用于绘制的设备上下文

SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;

// 绘制图标
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
以下部分为自己填写 CPaintDC dc(this);
CBitmap bmp;
bmp.CreateCompatibleBitmap(&dc,300,300);
CDC memDC;
memDC.CreateCompatibleDC(&dc);
memDC.SelectObject(&bmp);

// 使图标在工作区矩形中居中

int x1,x2,y1,y2,r=2,xx,yy,x,y;

CPen pen;
pen.CreatePen(PS_SOLID,2,RGB(0,0,255));
CPen *oldpen=(CPen *)memDC.SelectObject(&pen);
CBrush brush;
brush.CreateSolidBrush(RGB(255,0,0));
x1=100;y1=100;x2=400;y2=400;
Ellipse (*memDC,x1,y1,x2,y2);
x=190;xx=x-20;
y=152;yy=y-20;
CBrush *oldbrush=(CBrush *)memDC.SelectObject(&brush);
Ellipse (*memDC,x,y,xx,yy);
ExtFloodFill(*memDC,x,y,RGB(255,0,0),RGB(255,0,0));
dc.BitBlt(0,0,300,300,&memDC,0,0,SRCCOPY);
bmp.DeleteObject();
memDC.DeleteDC();

}

}

[Eleven]

void CXXDlg::OnPaint() 
{
	CPaintDC dc(this); // device context for painting

	if (IsIconic())
	{
		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CBitmap bmp;
		CRect rc;
		GetClientRect(rc);
		bmp.CreateCompatibleBitmap(&dc,rc.Width(),rc.Height());
		CDC memDC;
		memDC.CreateCompatibleDC(&dc);
		memDC.SelectObject(&bmp);	
		
		CPoint pt(rc.CenterPoint());
		const int WIDTH = 300;
		const int HEIGHT = 300;
		const int WIDTH2 = 100;
		const int HEIGHT2 = 100;

		int x1 = pt.x - WIDTH / 2;
		int y1 = pt.y - HEIGHT / 2;
		int x2 = pt.x + WIDTH / 2;
		int y2 = pt.y + HEIGHT / 2;
		
		
		CPen pen;
		pen.CreatePen(PS_SOLID,2,RGB(0,0,255));
		CPen *oldpen=(CPen *)memDC.SelectObject(&pen);
		CBrush brush;
		brush.CreateSolidBrush(RGB(255,0,0));
		CBrush *oldbrush=(CBrush *)memDC.SelectObject(&brush);
	
		memDC.FillSolidRect(0, 0, rc.Width(), rc.Height(), GetSysColor(COLOR_3DFACE));

		memDC.Ellipse(x1,y1,x2,y2);

 		int x3 = pt.x - WIDTH2 / 2;
		int y3 = pt.y - HEIGHT2 / 2;
		int x4 = pt.x + WIDTH2 / 2;
		int y4 = pt.y + HEIGHT2 / 2;
		pen.DeleteObject();
		pen.CreatePen(PS_SOLID, 2, RGB(255, 255, 128));
		oldpen = (CPen*)memDC.SelectObject(&pen);
		brush.DeleteObject();
		brush.CreateSolidBrush(RGB(0, 255, 0));
		oldbrush=(CBrush *)memDC.SelectObject(&brush);

		memDC.Ellipse(x3, y3, x4, y4);
		
		dc.BitBlt(0,0,rc.Width(),rc.Height(),&memDC,0,0,SRCCOPY);
		memDC.SelectObject(oldpen);
		memDC.SelectObject(oldbrush);
		bmp.DeleteObject();
		memDC.DeleteDC();

		//CDialog::OnPaint();
	}
}

[susuding]

多谢多谢，很有用呀！在问一句，什么时候在else后写代码，什么时候在if后面写，若是在按某个按钮后，调用该程序，该把代码写再哪呢？谢谢指导啊，实在是初学，不大懂哈

[Eleven]

什么时候在else后写代码，什么时候在if后面写，若是在按某个按钮后，调用该程序，该把代码写再哪呢？
----------------------------------------------------------------
囧，看你问题，我是相当的无语。。。
什么时候在if后面写，当然是满足if条件的时候，不满足就在else里写了

若是在按某个按钮后，调用该程序，该把代码写再哪呢？
在按钮的响应函数中去调用。。。

[susuding]

是在是太菜鸟了，丢人了！没看懂if后面写的是什么!以后还得找大侠请教呀，别嫌我烦哈！

[cfk2011]

VisualEleven 是高手啊，呵呵，学习了！！！