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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

  • 1
    @Joseph please post your comment as an answer so this thread can be marked as solved – underdark Jul 12 '18 at 19:21
  • @gHupf - Most welcome, glad it helped! Will post the comment as an answer as suggested by underdark :) – Joseph Jul 13 '18 at 10:45
1

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()

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