QGraphicsProxyWidget embeds QWidget-based widgets, for example, a QPushButton, QFontComboBox, or even QFileDialog, into QGraphicsScene. It forwards events between the two objects and translates between QWidget's integer-based geometry and QGraphicsWidget's qreal-based geometry. QGraphicsProxyWidget supports all core features of QWidget, including tab focus, keyboard input, Drag & Drop, and popups. You can also embed complex widgets, e.g., widgets with subwidgets.
上面是摘自qt手册里 说了QGraphicsProxyWidget 负责将事件在widget和scene之间进行传递,而且支持qwidget的所有特性。所以用setFocus()应该没错。可以试着用qapplication::focusWidget ()推测下谁当前拥有焦点
PS:白天忙 没时间回你