首先调用SystemGc()获取图形上下文，SystemGc()是CCoeControl的一个成员函数；然后设置相应的图形上下文项；最后调用绘图函数DrawRect()画一个矩形。

所有的绘图都是通过图形上下文(graphics context,GC)来完成的。在Symbian OS中，定义了一个抽象类CGraphicsContext来统一图形上下文的接口，为设备无关的绘图提供了丰富的API。-First Call SystemGc () to obtain a graphics context, SystemGc () is a member function CCoeControl　then set the appropriate graphics context item　last call drawing functions DrawRect () draw a rectangle. All graphics are the context through graphics (graphics context, GC) to complete. In Symbian OS, the definition of an abstract class CGraphicsContext graphics context to unify the interface for device-independent graphics to provide a rich API.