In file included from ..\Meexercise\/listwindow.h:8,

from ..\Meexercise\/groupwindow.h:5,

from ..\Meexercise\/mainwindow.h:6,

from ..\Meexercise\main.cpp:2:

..\Meexercise\/listdelegate.h:10: error: redefinition of 'class ListDelegate'

..\Meexercise\/listdelegate.h:11: error: previous definition of 'class ListDelegate'

Line 10 &11 in listdelegate.h is:
class ListDelegate : public QAbstractItemDelegate
{

thank you for your help!