Question

Recently, I am studying Symbian development. When I want to use CDirectScreenAccess to draw on the device directly, there occurs the question.
My code is below :

//MySnakeAppView.h
class CMySnakeAppView : public CCoeControl
{
...
private:
void ConstructL(const TRect& aRect);
CDirectScreenAccess* iDSA;
void Restart(RDirectScreenAccess::TTerminationReasons aReason);
void AbortNow(RDirectScreenAccess::TTerminationReasons aReason);
void DrawGraphics();
...
}

//MySnakeAppView.cpp

void CMySnakeAppView::ConstructL(const TRect& aRect)
    {
// Create a window for this application view
CreateWindowL();

// Set the windows size
SetRect(aRect);

// Activate the window, which makes it ready to be drawn
ActivateL();


CEikonEnv* env = CEikonEnv::Static();
iDSA = CDirectScreenAccess::NewL(env->WsSession(), *env->ScreenDevice(), Window(), *this);

iDSA->StartL();
DrawGraphics();
}
void CMySnakeAppView::DrawGraphics()
    {
CFbsBitGc *gc = iDSA->Gc();
TRgb colorRed = AKN_LAF_COLOR(35);
gc->SetPenColor(colorRed);
gc->DrawRect(TRect(0,0,100,100));
iDSA->ScreenDevice()->Update();

}
void CMySnakeAppView::Restart(RDirectScreenAccess::TTerminationReasons aReason)
    {

    iDSA->StartL();
    DrawGraphics();
    } 
void CMySnakeAppView::AbortNow(RDirectScreenAccess::TTerminationReasons aReason)
    {

    iDSA->Cancel();
    }

when I build this project, it is wrong with the code
iDSA = CDirectScreenAccess::NewL(env->WsSession(), *env->ScreenDevice(), Window(), *this);
this is a mistake writing that :
‘MDirectScreenAccess &’
– illegal implicit conversion from
‘CMySnakeAppView’ to
but when I do it like this ：
iDSA = CDirectScreenAccess::NewL(env->WsSession(), *env->ScreenDevice(), Window(), (MDirectScreenAccess &)*this);

there is no mistake in building,but still have mistake in the project, I don’t know why,I need your help

Answer 1

Your CMySnakeAppView should derive from MDirectScreenAccess – it looks like you’re already implementing the right methods, you’re just missing the declaration:

class CMySnakeAppView : public CCoeControl, public MDirectScreenAccess