QMenu撕纸菜单动作消失了吗？

Question

为什么我撕掉菜单后QMenu动作消失了？

之前：

之后：

import os, sys
from PySide import QtGui, QtCore

class QFilterButton(QtGui.QPushButton):

    def __init__(self, *args, **kwargs):
        super(QFilterButton, self).__init__(*args, **kwargs)

        # controls
        self.ui_search = QtGui.QLineEdit()
        self.ui_search.setPlaceholderText('Search...')
        self.ui_list = QtGui.QListView()
        self.ui_clear = QtGui.QPushButton('Clear')

        # lay main
        lay_main = QtGui.QVBoxLayout()
        lay_main.addWidget(self.ui_search)
        lay_main.addWidget(self.ui_list)
        lay_main.addWidget(self.ui_clear)
        widget = QtGui.QWidget()
        widget.setLayout(lay_main)

        # create flyout menu
        act_widget = QtGui.QWidgetAction(self)
        act_widget.setDefaultWidget(widget)

        self.menu = QtGui.QMenu(self)
        self.menu.setTearOffEnabled(True)
        self.menu.setWindowTitle('Filters')
        self.menu.addAction(act_widget)
        self.setMenu(self.menu)
        self.setText('Status (12)')



app = QtGui.QApplication(sys.argv)
lay = QtGui.QVBoxLayout()
lay.addWidget(QFilterButton())
ex = QtGui.QWidget()
ex.setLayout(lay)
ex.show()
sys.exit(app.exec_())