How to Add Callbacks for a QTWidget in ROS?

I am intending to develop a user interface using rqt in ros. I have developed a user interface containing a QTPushButton and QTLabel in QT Designer. I have imported this ui file into my Python Plugin. So, when I run the plugin, the user interface does pop up. But now I want to add a callback to the PushButton. So, that if I press the Button then the label should show the text "Button Clicked". I have tried many code snippets, but somehow nothing happens when I click the Button. Can somebody please help. It is very urgent. Can somebody write the actual code for the callback. My Plugin.py file is given below: import os import rospy import rospkg from qt_gui.plugin import Plugin from python_qt_binding import loadUi from python_qt_binding.QtGui import QWidget, QPushButton, QLabel class MyPlugin(Plugin): def __init__(self, context): super(MyPlugin, self).__init__(context) self.setObjectName('MyPlugin') from argparse import ArgumentParser parser = ArgumentParser() parser.add_argument("-q", "--quiet", action="store_true", dest="quiet", help="Put plugin in silent mode") args, unknowns = parser.parse_known_args(context.argv()) if not args.quiet: print 'arguments: ', args print 'unknowns: ', unknowns # Create QWidget self._widget = QWidget() # Get path to UI file which should be in the "resource" folder of this package ui_file = os.path.join(rospkg.RosPack().get_path('rqt_mypkg'), 'resource', 'mainwindow.ui') # Extend the widget with all attributes and children from UI file loadUi(ui_file, self._widget) # Give QObjects reasonable names self._widget.setObjectName('MyPluginUi') # Show _widget.windowTitle on left-top of each plugin (when # it's set in _widget). This is useful when you open multiple # plugins at once. Also if you open multiple instances of your # plugin at once, these lines add number to make it easy to # tell from pane to pane. if context.serial_number() > 1: self._widget.setWindowTitle(self._widget.windowTitle() + (' (%d)' % context.serial_number())) # Add widget to the user interface context.add_widget(self._widget) self.text = QLabel("Data") pushButton = QPushButton("Click Here") pushButton.clicked.connect(self.buttonClicked) def buttonClicked(self): print("Button Clicked") self.text.setText("Button Has been Clicked") Also, my ui file looks like this "mainwindow.ui": Form00400300Form801809827PushButton100806617TextLabel