不能转换'classname::glutKeyboard'从类型'void (classname::)(无符号char, int, int)'到类型'void(*)(无符号char, int, int)'

I have create a kinect application in c++, but i have same error in my glut functions, void glutKeyboard, glutDisplay, glutIdle. in following example i'm the all function is declared in the main file, so no need class, but in my application need, however the class generates an error by declaring the scope of functions.I have create a kinect application in c++, but