未调用OnDraw

Question

我正在尝试在CScrollView-derived类中显示图像：

C++ CScrollView, how to scroll an image?

所以我想重写OnDraw，把代码从OnPaint移到OnDraw。但是我不能。每次我调用Invalidate()时，只有OnPaint被调用。

void CCardioAppView::OnDraw(CDC* pDC)
{

}

void CCardioAppView::OnPaint()
{
    if (theApp.ImageFolderPath == _T("")) return;
//---------------------метод № 2 с CPictureHolder-------------------------------
    CPaintDC dc(this);
    CBitmap bmp;
    BITMAP b;
    HBITMAP hbitmap;
    CRect rect;
    auto bmp_iter = theApp.FullBmpMap.find(m_iCurrentImage);

    if (bmp_iter == theApp.FullBmpMap.end()) return;

    hbitmap = bmp_iter->second; 
    bmp.Attach((*bmp_iter).second);
    bmp.GetObject(sizeof(BITMAP), &b);

    GetClientRect(&rect);
    scaleRect = rect;
    OriginalWidth = b.bmWidth;
    OriginalHeight = b.bmHeight;
    if (rect.Height() <= b.bmHeight)
        scaleRect.right = rect.left + ((b.bmWidth*rect.Height()) / b.bmHeight);
    else if (rect.Height() > b.bmHeight)
    {
        scaleRect.right = b.bmWidth;
        scaleRect.bottom = b.bmHeight;
    }
    scaleRect.right = scaleRect.right + scale_koef_g;
    scaleRect.bottom = scaleRect.bottom + scale_koef_v;

    pic.CreateFromBitmap(hbitmap);
    pic.Render(&dc, scaleRect, rect);

    (*bmp_iter).second.Detach();
    (*bmp_iter).second.Attach(bmp);
    bmp.Detach();

    int isclWidth = scaleRect.Width();
    int isclHeight = scaleRect.Height();
    int irHeight = rect.Height();
    int irWidth = rect.Width();

    if ((isclWidth> irWidth)||(isclHeight > irHeight))
    {
        SetScrollSizes(MM_TEXT, CSize(isclWidth, isclHeight));
    }
    else SetScrollSizes(MM_TEXT, CSize(irWidth, irHeight));
}

Answer 1

当然它不会调用OnDraw()。当您调用Invalidate()时，它以CView派生类的WM_PAINT消息结束。CView::OnPaint()的默认实现获得一个paint DC，然后调用CView::OnDraw()。您正在重写OnPaint()，并且从未在OnPaint()处理程序中调用OnDraw()。

除了像CPaintDC dc(this);这样显而易见的东西之外，您可以将一些OnPaint()代码转移到OnDraw()中

之后，您可以删除您的OnPaint()声明和实现。然后，删除您的ON_WM_PAINT()消息映射条目。我不能保证你的绘图代码。