widget_button.py

# -*- coding: utf-8 -*-
from PyQt4 import QtCore, QtGui
from qgis.gui import QgsMessageBar
import widget_button_dialog


class WidgetButton(QtGui.QDialog):

    def __init__(self):
        QtGui.QDialog.__init__(self)
        # Set up the user interface from Designer.
        # After setupUI you can access any designer object by doing:
        # self.<objectname>
        self.ui = widget_button_dialog.Ui_Dialog()
        self.ui.setupUi(self)

    def openForm(self):
        self.show()

    def testSignal(self):

        iface.messageBar().pushMessage("Aviso: ",
                                       u"El botón ha sido clickado",
                                       QgsMessageBar.INFO, 5)

        self.close()

# Create the dialog and keep reference
reload(widget_button_dialog)
dlg = WidgetButton()

dlg.openForm()

btn = dlg.ui.pushButton

print btn.objectName()

btn.clicked.connect(dlg.testSignal)