diff --git a/activity_browser/app/ui/main.py b/activity_browser/app/ui/main.py
index e91422bdd..75031b6ee 100644
--- a/activity_browser/app/ui/main.py
+++ b/activity_browser/app/ui/main.py
@@ -9,7 +9,6 @@
 from .panels import LeftPanel, RightPanel
 from .statusbar import Statusbar
 from .utils import StdRedirector
-from ..signals import signals
 
 
 class MainWindow(QtWidgets.QMainWindow):
@@ -83,7 +82,9 @@ def __init__(self):
 
         # Layout: extra items outside main layout
         self.menu_bar = MenuBar(self)
-        self.statusbar = Statusbar(self)
+        self.setMenuBar(self.menu_bar)
+        self.status_bar = Statusbar(self)
+        self.setStatusBar(self.status_bar)
 
         self.connect_signals()
 
diff --git a/activity_browser/app/ui/menu_bar.py b/activity_browser/app/ui/menu_bar.py
index 3d2a312a4..45776423b 100644
--- a/activity_browser/app/ui/menu_bar.py
+++ b/activity_browser/app/ui/menu_bar.py
@@ -1,6 +1,4 @@
 # -*- coding: utf-8 -*-
-import json
-
 import brightway2 as bw
 from PySide2 import QtCore, QtWidgets, QtGui
 
@@ -11,29 +9,40 @@
 from .wizards.settings_wizard import SettingsWizard
 from .wizards.db_export_wizard import DatabaseExportWizard
 
-# TODO: Revise this entire class by subclassing QMenuBar
-
 
-class MenuBar(object):
+class MenuBar(QtWidgets.QMenuBar):
     def __init__(self, window):
+        super().__init__(parent=window)
         self.window = window
+        self.settings_wizard = None
+        self.export_wizard = None
+        self.biosphere_updater = None
+        self.file_menu = QtWidgets.QMenu('&File', self.window)
+        self.view_menu = QtWidgets.QMenu('&View', self.window)
+        self.windows_menu = QtWidgets.QMenu('&Windows', self.window)
+        self.help_menu = QtWidgets.QMenu('&Help', self.window)
+
         self.update_biosphere_action = QtWidgets.QAction(
             window.style().standardIcon(QtWidgets.QStyle.SP_BrowserReload),
             "&Update biosphere...", None
         )
-        self.biosphere_updater = None
+        self.export_db_action = QtWidgets.QAction(
+            self.window.style().standardIcon(QtWidgets.QStyle.SP_DriveHDIcon),
+            "&Export database...", None
+        )
         self.import_db_action = QtWidgets.QAction(
             qicons.import_db, '&Import database...', None
         )
 
-        self.menubar = QtWidgets.QMenuBar()
-        self.menubar.addMenu(self.setup_file_menu())
-        # self.menubar.addMenu(self.setup_tools_menu())
-        # self.menubar.addMenu(self.setup_extensions_menu())
-        self.menubar.addMenu(self.setup_view_menu())
-        self.menubar.addMenu(self.setup_windows_menu())
-        self.menubar.addMenu(self.setup_help_menu())
-        window.setMenuBar(self.menubar)
+        self.addMenu(self.file_menu)
+        self.addMenu(self.view_menu)
+        self.addMenu(self.windows_menu)
+        self.addMenu(self.help_menu)
+
+        self.setup_file_menu()
+        self.setup_view_menu()
+        self.update_windows_menu()
+        self.setup_help_menu()
         self.connect_signals()
 
     def connect_signals(self):
@@ -41,52 +50,40 @@ def connect_signals(self):
         signals.project_selected.connect(self.biosphere_exists)
         signals.databases_changed.connect(self.biosphere_exists)
         self.update_biosphere_action.triggered.connect(self.update_biosphere)
+        self.export_db_action.triggered.connect(self.transfer_database_wizard)
         self.import_db_action.triggered.connect(lambda: signals.import_database.emit(self.window))
 
-    # FILE
-    def setup_file_menu(self):
-        menu = QtWidgets.QMenu('&File', self.window)
-        menu.addAction(self.import_db_action)
-        menu.addAction(
-            self.window.style().standardIcon(QtWidgets.QStyle.SP_DriveHDIcon),
-            "&Export database...",
-            self.transfer_database_wizard
-        )
-        menu.addAction(self.update_biosphere_action)
-        menu.addAction(
+    def setup_file_menu(self) -> None:
+        """Build the menu for specific importing/export/updating actions."""
+        self.file_menu.addAction(self.import_db_action)
+        self.file_menu.addAction(self.export_db_action)
+        self.file_menu.addAction(self.update_biosphere_action)
+        self.file_menu.addAction(
             qicons.settings,
             '&Settings...',
             self.open_settings_wizard
         )
-        return menu
 
-    # VIEW
-    def setup_view_menu(self):
-        view_menu = QtWidgets.QMenu('&View', self.window)
-        view_menu.addAction(
+    def setup_view_menu(self) -> None:
+        """Build the menu for viewing or hiding specific tabs"""
+        self.view_menu.addAction(
             qicons.graph_explorer,
             '&Graph Explorer',
             lambda x="Graph Explorer": signals.toggle_show_or_hide_tab.emit(x)
         )
-        view_menu.addAction(
+        self.view_menu.addAction(
             qicons.history,
             '&Activity History',
             lambda x="History": signals.toggle_show_or_hide_tab.emit(x)
         )
-        view_menu.addAction(
+        self.view_menu.addAction(
             qicons.welcome,
             '&Welcome screen',
             lambda x="Welcome": signals.toggle_show_or_hide_tab.emit(x)
         )
-        return view_menu
-
-    # WINDOWS
-    def setup_windows_menu(self):
-        self.windows_menu = QtWidgets.QMenu('&Windows', self.window)
-        self.update_windows_menu()
-        return self.windows_menu
 
     def update_windows_menu(self):
+        """Clear and rebuild the menu for switching between tabs."""
         self.windows_menu.clear()
         for index in range(self.window.stacked.count()):  # iterate over widgets in QStackedWidget
             widget = self.window.stacked.widget(index)
@@ -96,25 +93,22 @@ def update_windows_menu(self):
                 lambda widget=widget: self.window.stacked.setCurrentWidget(widget),
             )
 
-    # HELP
-    def setup_help_menu(self):
-        help_menu = QtWidgets.QMenu('&Help', self.window)
-        help_menu.addAction(
+    def setup_help_menu(self) -> None:
+        """Build the help menu for the menubar."""
+        self.help_menu.addAction(
             self.window.icon,
             '&About Activity Browser',
             self.about)
-        help_menu.addAction(
+        self.help_menu.addAction(
             '&About Qt',
             lambda: QtWidgets.QMessageBox.aboutQt(self.window)
         )
-        help_menu.addAction(
+        self.help_menu.addAction(
             qicons.issue,
             '&Report an idea/issue on GitHub',
             self.raise_issue_github
         )
 
-        return help_menu
-
     def about(self):
         text = """
 Activity Browser - a graphical interface for Brightway2.<br><br>
@@ -144,13 +138,13 @@ def about(self):
 
     def raise_issue_github(self):
         url = QtCore.QUrl('https://github.com/LCA-ActivityBrowser/activity-browser/issues/new')
-        QtGui.QDesktopServices.openUrl(url)
+        QtGui.QDesktopServices.openUrl(url=url)
 
     def open_settings_wizard(self):
-        self.settings_wizard = SettingsWizard()
+        self.settings_wizard = SettingsWizard(self.window)
 
     def transfer_database_wizard(self) -> None:
-        wizard = DatabaseExportWizard()
+        self.export_wizard = DatabaseExportWizard(self.window)
 
     def biosphere_exists(self) -> None:
         """ Test if the default biosphere exists as a database in the project
@@ -166,8 +160,8 @@ def update_biosphere(self):
         ok = QtWidgets.QMessageBox.question(
             self.window, "Update biosphere3?",
             "Updating the biosphere3 database cannot be undone!",
-            buttons=QtWidgets.QMessageBox.Ok | QtWidgets.QMessageBox.Abort,
-            defaultButton=QtWidgets.QMessageBox.Abort
+            QtWidgets.QMessageBox.Ok | QtWidgets.QMessageBox.Abort,
+            QtWidgets.QMessageBox.Abort
         )
         if ok == QtWidgets.QMessageBox.Ok:
-            self.biosphere_updater = BiosphereUpdater()
+            self.biosphere_updater = BiosphereUpdater(self.window)
diff --git a/activity_browser/app/ui/statusbar.py b/activity_browser/app/ui/statusbar.py
index b0b0196c6..1b1ae3823 100644
--- a/activity_browser/app/ui/statusbar.py
+++ b/activity_browser/app/ui/statusbar.py
@@ -1,24 +1,22 @@
 # -*- coding: utf-8 -*-
-from PySide2 import QtWidgets
+from PySide2.QtCore import Slot
+from PySide2.QtWidgets import QLabel, QStatusBar
 
-from brightway2 import projects
+import brightway2 as bw
 
 from ..signals import signals
 
 
-class Statusbar(object):
+class Statusbar(QStatusBar):
     def __init__(self, window):
-        self.window = window
-        self.statusbar = QtWidgets.QStatusBar()
-        self.window.setStatusBar(self.statusbar)
+        super().__init__(parent=window)
+        self.status_message_left = QLabel('Welcome')
+        self.status_message_right = QLabel('Database')
+        self.status_message_center = QLabel('Project')
 
-        self.status_message_left = QtWidgets.QLabel('Welcome')
-        self.status_message_right = QtWidgets.QLabel('Database')
-        self.status_message_center = QtWidgets.QLabel('Project')
-
-        self.statusbar.addWidget(self.status_message_left, 1)
-        self.statusbar.addWidget(self.status_message_center, 2)
-        self.statusbar.addWidget(self.status_message_right, 0)
+        self.addWidget(self.status_message_left, 1)
+        self.addWidget(self.status_message_center, 2)
+        self.addWidget(self.status_message_right, 0)
 
         self.connect_signals()
 
@@ -27,21 +25,26 @@ def connect_signals(self):
         signals.project_selected.connect(self.update_project)
         signals.database_selected.connect(self.set_database)
 
-    def left(self, message):
+    @Slot(str, name="statusLeft")
+    def left(self, message: str) -> None:
         print(message)  # for console output
         if isinstance(message, str):
             self.status_message_left.setText(message)
 
+    @Slot(str, name="statusCenter")
     def center(self, message):
         self.status_message_center.setText(message)
 
+    @Slot(str, name="statusRight")
     def right(self, message):
         self.status_message_right.setText(message)
 
+    @Slot(name="updateProjectStatus")
     def update_project(self):
-        name = projects.current
+        name = bw.projects.current
         self.center("Project: {}".format(name))
         self.right("Database: None")
 
+    @Slot(str, name="setDatabaseName")
     def set_database(self, name):
         self.right("Database: {}".format(name))
diff --git a/activity_browser/app/ui/widgets/biosphere_update.py b/activity_browser/app/ui/widgets/biosphere_update.py
index e2f39121f..841e171d3 100644
--- a/activity_browser/app/ui/widgets/biosphere_update.py
+++ b/activity_browser/app/ui/widgets/biosphere_update.py
@@ -12,8 +12,8 @@
 
 
 class BiosphereUpdater(QtWidgets.QProgressDialog):
-    def __init__(self):
-        super().__init__()
+    def __init__(self, parent=None):
+        super().__init__(parent=parent)
         self.setWindowTitle("Updating '{}' database".format(bw.config.biosphere))
         self.setLabelText("Adding new flows to biosphere database")
         self.setRange(0, 0)