cómo cargar QGIS openlayers_plugin en un script de Python independiente (no la consola de Python incrustada de QGIS)

si trato de cargar el complemento de capas abiertas en una aplicación independiente, siempre falla con False, aunque las rutas están configuradas y el complemento se muestra disponible.

(probado en Ubuntu 14.04, QGIS 2.4, python-2.7)

#!/usr/bin/python
# -*- coding: utf-8 -*-

import sys, os

import qgis
import qgis.gui, qgis.utils
from qgis.core import *
from PyQt4 import QtGui


# open an app
app = QtGui.QApplication(sys.argv)
# supply path to where is your qgis installed
QgsApplication.setPrefixPath(u'/usr', True)
# load providers
QgsApplication.initQgis()

# set up the plugins
qgis.utils.plugin_paths = \
    ['/usr/share/qgis/python/plugins',
    os.path.expanduser('~/.qgis2/python/plugins'),]
qgis.utils.updateAvailablePlugins()
print qgis.utils.available_plugins
print "...load:", qgis.utils.loadPlugin(u'openlayers_plugin')
print "...start:", qgis.utils.startPlugin(u'openlayers_plugin')
print "active:\n",qgis.utils.active_plugins

canvas = qgis.gui.QgsMapCanvas()
canvas.show()

Cuál es el problema aquí ? post ¿Cómo recuperar capas de capas abiertas de pyqgis? se refiere a la consola de Python incrustada, donde el complemento estaba mágicamente disponible antes.

¡Gracias!

Esto nunca, bueno, tal vez con algunos hacks, va a funcionar bien. Los complementos normalmente usan el QgisInterfaceobjeto que da acceso a la interfaz y métodos de QGIS. No tiene este objeto en su secuencia de comandos independiente. La mayoría de los complementos, si no todos, no están diseñados para ejecutarse fuera de QGIS como este.

Siendo muy entusiasta con el paradigma TDD, pasé un tiempo armando una interfaz ficticia (basada en algunos fragmentos de código que encontré en Internet) que permite llamar a QGIS y QGIS-plugins de manera independiente.

La interfaz que se me ocurrió se ve de la siguiente manera y la utilicé para todas mis pruebas unitarias desde:

# coding=utf-8
"""QGIS plugin implementation.

.. note:: This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.

.. note:: The basis of this source code was copied from the 'postgis viewer' application
     with original authors:
     Copyright (c) 2010 by Ivan Mincik, [email protected]
     Copyright (c) 2011 German Carrillo, [email protected]
     Copyright (c) 2014 Tim Sutton, [email protected]

"""
from qgis._core import QgsVectorLayer
from PyQt4.QtCore import QObject, pyqtSlot, pyqtSignal, QCoreApplication, QSize
from PyQt4.QtGui import QWidget
from qgis.core import QgsMapLayerRegistry, QgsApplication, QgsVectorLayer
from qgis.gui import QgsMapCanvasLayer, QgsMapCanvas

import logging
import sys

from mole import config

LOGGER = logging.getLogger('QGIS')


def set_up_interface():
    """
    Sets up a QGIS pseudo-application which enables calling methods as if when calling them from QGIS-console.

    :return qgis_app: Pseudo QGIS-instance
    :rtype: QgsApplication
    :return canvas: The map canvas
    :rtype: QgsMapCanvas
    :return iface: A dummy interface, giving access to needed method-calls
    :rtype: QgisInterface
    """
    gui_flag = True  # All test will run qgis in gui mode
    qgis_app = QgsApplication(sys.argv, gui_flag)
    prefix_path = config.qgis_prefix_path()
    qgis_app.setPrefixPath(prefix_path, True)
    qgis_app.initQgis()
    QCoreApplication.setOrganizationName('QGIS')
    QCoreApplication.setApplicationName('QGIS2')

    # parent = QWidget()
    # canvas = QgsMapCanvas(parent)
    # canvas.resize(QSize(400, 400))
    canvas = MyMapCanvas()

    iface = QgisInterface(canvas)

    return qgis_app, canvas, iface

#noinspection PyMethodMayBeStatic,PyPep8Naming
class QgisInterface(QObject):
    """Class to expose QGIS objects and functions to plugins.

    This class is here for enabling us to run unit tests only,
    so most methods are simply stubs.
    """
    currentLayerChanged = pyqtSignal(QgsMapCanvasLayer)

    def __init__(self, canvas):
        """Constructor
        :param canvas:
        """
        QObject.__init__(self)
        self.canvas = canvas
        self.legend_interface = MyLegendInterface()
        self.active_layer = None
        # Set up slots so we can mimic the behaviour of QGIS when layers
        # are added.
        LOGGER.debug('Initialising canvas...')
        # noinspection PyArgumentList
        QgsMapLayerRegistry.instance().layersAdded.connect(self.addLayer)
        # noinspection PyArgumentList
        QgsMapLayerRegistry.instance().layerWasAdded.connect(self.addLayer)
        # noinspection PyArgumentList
        QgsMapLayerRegistry.instance().removeAll.connect(self.removeAllLayers)

        # For processing module
        self.destCrs = None


    @pyqtSlot('QgsMapLayer')
    def addLayer(self, layer):
        """Handle a layer being added to the registry so it shows up in canvas.

        :param layer: list<QgsMapLayer> list of map layers that were added

        .. note: The QgsInterface api does not include this method, it is added
                 here as a helper to facilitate testing.

        .. note: The addLayer method was deprecated in QGIS 1.8 so you should
                 not need this method much.
        """
        # set the recently added layer as active
        # LOGGER.debug('Layer Count Before: %s' % len(self.canvas.layers()))
        current_layers = self.canvas.layers()
        final_layers = [] + current_layers
        final_layers.append(QgsMapCanvasLayer(layer))
        self.canvas.setLayerSet(final_layers)
        self.active_layer = layer

    @pyqtSlot()
    def removeAllLayers(self):
        """Remove layers from the canvas before they get deleted."""
        self.canvas.setLayerSet([])

    def newProject(self):
        """Create new project."""
        # noinspection PyArgumentList
        QgsMapLayerRegistry.instance().removeAllMapLayers()

    def legendInterface(self):
        """Get the legend."""
        return self.legend_interface

    def activeLayer(self):
        """Get pointer to the active layer (layer selected in the legend)."""
        return self.active_layer

    def setActiveLayer(self, layer):
        """Set the given layer as active.
        :param layer: Layer that shall be set active
        :type layer: QgsMapLayer
        """
        self.active_layer = layer

    class actionAddFeature(object):

        def __init__(self):
            pass

        def trigger(self):
            pass

    class actionZoomToLayer(object):

        def __init__(self):
            pass

        def trigger(self):
            pass

    # ---------------- API Mock for QgsInterface follows -------------------
    def zoomFull(self):
        """Zoom to the map full extent."""
        pass

    def zoomToPrevious(self):
        """Zoom to previous view extent."""
        pass

    def zoomToNext(self):
        """Zoom to next view extent."""
        pass

    def zoomToActiveLayer(self):
        """Zoom to extent of active layer."""
        pass

    def addVectorLayer(self, path, base_name, provider_key):
        """Add a vector layer.

        :param path: Path to layer.
        :type path: str

        :param base_name: Base name for layer.
        :type base_name: str

        :param provider_key: Provider key e.g. 'ogr'
        :type provider_key: str
        """
        pass

    def addRasterLayer(self, path, base_name):
        """Add a raster layer given a raster layer file name

        :param path: Path to layer.
        :type path: str

        :param base_name: Base name for layer.
        :type base_name: str
        """
        pass

    def addToolBarIcon(self, action):
        """Add an icon to the plugins toolbar.

        :param action: Action to add to the toolbar.
        :type action: QAction
        """
        pass

    def removeToolBarIcon(self, action):
        """Remove an action (icon) from the plugin toolbar.

        :param action: Action to add to the toolbar.
        :type action: QAction
        """
        pass

    def addToolBar(self, name):
        """Add toolbar with specified name.

        :param name: Name for the toolbar.
        :type name: str
        """
        pass

    def mapCanvas(self):
        """Return a pointer to the map canvas."""
        return self.canvas

    def mainWindow(self):
        """Return a pointer to the main window.

        In case of QGIS it returns an instance of QgisApp.
        """
        pass

    def addDockWidget(self, area, dock_widget):
        """Add a dock widget to the main window.

        :param area: Where in the ui the dock should be placed.
        :type area:

        :param dock_widget: A dock widget to add to the UI.
        :type dock_widget: QDockWidget
        """
        pass


class MyLegendInterface(object):

    def __init__(self):
        self.layer_visibility = {}

    def setLayerVisible(self, layer, yes_no):
        self.layer_visibility[layer.name()] = yes_no

    def isLayerVisible(self, layer):
        try:
            return self.layer_visibility[layer.name()]
        except KeyError:
            print('Layer {} has not been set (in)visible yet.'.format(layer.name()))
            return False


class MyMapCanvas(object):

    def __init__(self):
        self.layer_set = []

    def layers(self):
        return self.layer_set

    def layer(self, index):
        layer = self.layer_set[index].layer()
        return layer

    def setLayerSet(self, layer_set):
        self.layer_set = layer_set

    def layerCount(self):
        return len(self.layer_set)

Si desea probar / usar QGIS más la interacción con un complemento instalado ahora, haga lo siguiente (en su configuración de prueba de unidad, por ejemplo):

qgis_app, canvas, iface = set_up_interface()
plugin_name = 'openlayers_plugin'
utils.plugin_paths = [os.path.expanduser('~/.qgis2/python/plugins')]
utils.updateAvailablePlugins()
utils.loadPlugin(plugin_name)
utils.iface = self.iface
utils.startPlugin(plugin_name) 

Para obtener más ejemplos de uso y ejemplos de la vida real sobre aplicaciones QGIS de prueba de unidades, puede consultar nuestra página github ( https://github.com/UdK-VPT/Open_eQuarter/tree/master/mole ). Las pruebas de carpeta contienen todas las pruebas unitarias (que en su mayoría prueban los módulos en el paquete qgisinteraction, que contiene un módulo, que interactúa con el plugin point_sampling_tool-plugin).