Why does the button disappear when using QTreeView and QSortFilterProxyModel ?

hi all, I used "setIndexWidget" to add a QPushButton into a column of QTreeView, and that was fine.

just like this:

m_pTreeView->setIndexWidget(m_pModel->index(irow, 4), pButton);

but, when I addd the filter function, and used it, like this:

m_pTreeView->seIndexWiget(m_pFilterModel->mapFormSource(m_pModel->indexi(row, 4), pbutton);

and then I input some character into the lineEdit to filter the items, and all buttons in column 4 were gone !

the buttons disappeared !

so I don't know Why , thank you for your help!