使用Symbian dev的CDirectScreenAccess的问题
最近在研究Symbian开发。当我想使用CDirectScreenAccess直接在设备上绘图时，出现了问题。 我的代码如下：
//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();
}
当我构建这个项目时，代码是错误的 iDSA = CDirectScreenAccess::NewL(env->WsSession(), *env->ScreenDevice(), Window(), *this); 这是一个错误的写法： 'MDirectScreenAccess &' - 非法隐式转换 'CMySnakeAppView' 到 但是当我这样做时： iDSA = CDirectScreenAccess::NewL(env->WsSession(), *env->ScreenDevice(), Window(), (MDirectScreenAccess &)*this);
构建没有错误，但项目中仍然有错误，我不知道为什么，我需要你的帮助
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
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评论（2）
您的
CMySnakeAppView应该派生自MDirectScreenAccess- 看起来您已经实现了正确的方法，只是缺少声明：Your
CMySnakeAppViewshould derive fromMDirectScreenAccess- it looks like you're already implementing the right methods, you're just missing the declaration:您不能传递 *this，因为它不是 MDirectScreenAccess 类的实例，也不是从它继承的类的实例。您可以手动投射它，但这是一个错误。您应该构建一个继承自 MDirectScreenAccess 的类，并从那里构建 iDSA。请看这里：
http://www.developer.nokia.com/Community/Wiki /Anti-tearing_with_CDirectScreenBitmap
You can't pass *this, because it is not an istance of a MDirectScreenAccess class nor an istance of a class that inherits from it. You can cast it manually, but that is an error. You should construct a class that inherits from MDirectScreenAccess and from there build the iDSA. Look at here:
http://www.developer.nokia.com/Community/Wiki/Anti-tearing_with_CDirectScreenBitmap