QGraphicsTextItem cannot input chinese

env: Qt version: 5.5.0 mingw
des:
when QGraphicsTextItem setTextInteractionFlags to Qt::TextEditorInteraction
then cannot input chinese, but if i minimize the mainwindow ,and then show again, this will work ok, it seems the editor lost the focus.

but at version 5.3.1 this will works fine.
this should be a bug.