QGIS – Fixing ‘NoneType’ Object Has No Attribute ‘attributeList’ in QGIS Plugin

pyqgispythonqgis

I try developing a QGIS plugin for the first time and I am stuck trying to connect the python code to the dockwidget and it's contents created in QT Designer. I created a QListView inside the dockwidget and I called it "attributeList". I try connecting it with

self.dockwidget.attributeList.clear()

If I start the plugin in QGIS I get the error "'NoneType' object has no attribute 'attributeList'"

My full code is the following:

def __init__(self, iface):
    """Constructor.

    :param iface: An interface instance that will be passed to this class
        which provides the hook by which you can manipulate the QGIS
        application at run time.
    :type iface: QgsInterface
    """
    # Save reference to the QGIS interface
    self.iface = iface

    # initialize plugin directory
    self.plugin_dir = os.path.dirname(__file__)

    # initialize locale
    locale = QSettings().value('locale/userLocale')[0:2]
    locale_path = os.path.join(
        self.plugin_dir,
        'i18n',
        'Selektion_{}.qm'.format(locale))

    if os.path.exists(locale_path):
        self.translator = QTranslator()
        self.translator.load(locale_path)

        if qVersion() > '4.3.3':
            QCoreApplication.installTranslator(self.translator)

    # Declare instance attributes
    self.actions = []
    self.menu = self.tr(u'&Selektion')
    # TODO: We are going to let the user set this up in a future iteration
    self.toolbar = self.iface.addToolBar(u'Selektion')
    self.toolbar.setObjectName(u'Selektion')

    #print "** INITIALIZING Selektion"

    self.pluginIsActive = False
    self.dockwidget = None


# noinspection PyMethodMayBeStatic
def tr(self, message):
    """Get the translation for a string using Qt translation API.

    We implement this ourselves since we do not inherit QObject.

    :param message: String for translation.
    :type message: str, QString

    :returns: Translated version of message.
    :rtype: QString
    """
    # noinspection PyTypeChecker,PyArgumentList,PyCallByClass
    return QCoreApplication.translate('Selektion', message)


def add_action(
    self,
    icon_path,
    text,
    callback,
    enabled_flag=True,
    add_to_menu=True,
    add_to_toolbar=True,
    status_tip=None,
    whats_this=None,
    parent=None):
    """Add a toolbar icon to the toolbar.

    :param icon_path: Path to the icon for this action. Can be a resource
        path (e.g. ':/plugins/foo/bar.png') or a normal file system path.
    :type icon_path: str

    :param text: Text that should be shown in menu items for this action.
    :type text: str

    :param callback: Function to be called when the action is triggered.
    :type callback: function

    :param enabled_flag: A flag indicating if the action should be enabled
        by default. Defaults to True.
    :type enabled_flag: bool

    :param add_to_menu: Flag indicating whether the action should also
        be added to the menu. Defaults to True.
    :type add_to_menu: bool

    :param add_to_toolbar: Flag indicating whether the action should also
        be added to the toolbar. Defaults to True.
    :type add_to_toolbar: bool

    :param status_tip: Optional text to show in a popup when mouse pointer
        hovers over the action.
    :type status_tip: str

    :param parent: Parent widget for the new action. Defaults None.
    :type parent: QWidget

    :param whats_this: Optional text to show in the status bar when the
        mouse pointer hovers over the action.

    :returns: The action that was created. Note that the action is also
        added to self.actions list.
    :rtype: QAction
    """

    icon = QIcon(icon_path)
    action = QAction(icon, text, parent)
    action.triggered.connect(callback)
    action.setEnabled(enabled_flag)

    if status_tip is not None:
        action.setStatusTip(status_tip)

    if whats_this is not None:
        action.setWhatsThis(whats_this)

    if add_to_toolbar:
        self.toolbar.addAction(action)

    if add_to_menu:
        self.iface.addPluginToMenu(
            self.menu,
            action)

    self.actions.append(action)

    return action


def initGui(self):
    """Create the menu entries and toolbar icons inside the QGIS GUI."""

    icon_path = ':/plugins/selektion/icon.png'
    self.add_action(
        icon_path,
        text=self.tr(u'selektion'),
        callback=self.run,
        parent=self.iface.mainWindow())
    self.attributes()

def attributes(self):
    self.dockwidget.attributeList.clear()

#--------------------------------------------------------------------------

def onClosePlugin(self):
    """Cleanup necessary items here when plugin dockwidget is closed"""

    #print "** CLOSING Selektion"

    # disconnects
    self.dockwidget.closingPlugin.disconnect(self.onClosePlugin)

    # remove this statement if dockwidget is to remain
    # for reuse if plugin is reopened
    # Commented next statement since it causes QGIS crashe
    # when closing the docked window:
    # self.dockwidget = None

    self.pluginIsActive = False


def unload(self):
    """Removes the plugin menu item and icon from QGIS GUI."""

    #print "** UNLOAD Selektion"

    for action in self.actions:
        self.iface.removePluginMenu(
            self.tr(u'&Selektion'),
            action)
        self.iface.removeToolBarIcon(action)
    # remove the toolbar
    del self.toolbar

#--------------------------------------------------------------------------

def run(self):
    """Run method that loads and starts the plugin"""

    if not self.pluginIsActive:
        self.pluginIsActive = True

        #print "** STARTING Selektion"

        # dockwidget may not exist if:
        #    first run of plugin
        #    removed on close (see self.onClosePlugin method)
        if self.dockwidget == None():
            # Create the dockwidget (after translation) and keep reference
            self.dockwidget = SelektionDockWidget()

        # connect to provide cleanup on closing of dockwidget
        self.dockwidget.closingPlugin.connect(self.onClosePlugin)

        # show the dockwidget
        # TODO: fix to allow choice of dock location
        self.iface.addDockWidget(Qt.RightDockWidgetArea, self.dockwidget)
        self.dockwidget.show()

You can find the line I mentioned right after the def initGui

Best Answer

The initGui() function is executed before your run() function which defines the actual dockwidget. Instead, you could place self.attributes() inside run() after the line:

self.dockwidget = SelektionDockWidget()
Related Question