PySide: Enabled QGraphicsView object doesn't take QMouseDoubleClickEvent

[hiroro]

I have this simple program in qt. It creates 2 small squares with qgraphicsview. One square is "Enabled" at initialization so it is painted blue and the other square is Disabled so it is white at the initialization. When I double click on the disabled square QMouseDoubleClickEvent is called and the square is enabled(turned to blue). But when I double click on the Enabled(blue) square, the double click event doesn't work. How can I make the double click work on the blue(Enabled) square? Thank you

import sys
from PySide import QtGui
from ui.Ui_MainWindow import Ui_MainWindow
from PySide.QtGui import QApplication

class MainWindow(QtGui.QMainWindow, Ui_MainWindow):
def init(self, parent=None):
QtGui.QMainWindow.init(self)
Ui_MainWindow.init(self)
self.setupUi(self)
self.graphicsView.setEnabled (False)
self.graphicsView_2.setEnabled(True)

def mouseDoubleClickEvent(self, event):
    self.graphicsView.setEnabled (True)
    self.graphicsView_2.setEnabled(True)

def main():
app = QApplication(sys.argv)
wnd = MainWindow()
wnd.show()
sys.exit(app.exec_())

if name == 'main':
main()