[Qgis-user] Problem refreshing map canvas with pyqgis

[Sylvie Perdriel]

Hello Every Body,



I’d like to develop a standalone application for air pollution modeling
based on pyqgis. I installed QGIs version 2.2 on windows 7 64bits from
osgeo installer and my development platform is Eclispe/pydev.

As a first step, I’m trying to load a shapefile and plot it on a
qgsmapcanvas (see attached python code) : the shapefile is properly  loaded
but I can see it plotted only after minimizing the window and restoring it.
I have tried to add repaint(), refresh() calls on the qgsmapcanvas or the
window without any success. I must surely miss something simple and would
appreciate some help if possible.

Thank you in advanced and best regards,



Sylvie
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import PyQt4.uic
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from qgis.core import QgsVectorLayer, QgsMapLayerRegistry, QgsApplication,QgsProviderRegistry 
from qgis.gui import *
import os
basepath="E:/TECHNIQUE/DEVCAIRN/PYTHON/UI/tests"
#
class Window(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        #PyQt4.uic.loadUi(os.path.join(basepath,'canvas.ui'), self)
        #self.canvas.setCanvasColor(Qt.yellow)
        #self.canvas.enableAntiAliasing(True)
        #self.setCentralWidget(self.canvas)
        self.setupGui()

        actionZoomIn = QAction(QString("Zoom in"), self)
        actionZoomOut = QAction(QString("Zoom out"), self)
        actionPan = QAction(QString("Pan"), self)

        actionZoomIn.setCheckable(True)
        actionZoomOut.setCheckable(True)
        actionPan.setCheckable(True)

        self.connect(actionZoomIn, SIGNAL("triggered()"), self.zoomIn)
        self.connect(actionZoomOut, SIGNAL("triggered()"), self.zoomOut)
        self.connect(actionPan, SIGNAL("triggered()"), self.pan)


        self.toolbar = self.addToolBar("Canvas actions")
        self.toolbar.addAction(actionZoomIn)
        self.toolbar.addAction(actionZoomOut)
        self.toolbar.addAction(actionPan)

        # create the map tools
        self.toolPan = QgsMapToolPan(self.canvas)
        self.toolPan.setAction(actionPan)
        self.toolZoomIn = QgsMapToolZoom(self.canvas, False) # false = in
        self.toolZoomIn.setAction(actionZoomIn)
        self.toolZoomOut = QgsMapToolZoom(self.canvas, True) # true = out
        self.toolZoomOut.setAction(actionZoomOut)

        self.pan()

    def setupGui(self):
        frame = QFrame(self)
        self.setCentralWidget(frame)
        self.grid_layout = QGridLayout(frame)

        self.canvas = QgsMapCanvas()
        self.canvas.setCanvasColor(QColor(255, 255, 255))  
        self.canvas.enableAntiAliasing(True)
        self.grid_layout.addWidget(self.canvas)
        # add tool bar
        self.toolbar = self.addToolBar("Map Tools")
    
    def loadLayer(self, path, name):
        if os.path.exists(path):
            if len(name)==0:
                (name, ext) = os.path.basename(path).split('.')
            layer = QgsVectorLayer(path, name, 'ogr')
            if not layer.isValid():
               raise IOError, "Failed to open the layer"
            #self.canvas.setExtent(layer.extent())
            QgsMapLayerRegistry.instance().addMapLayer(layer)
            #layers = self.canvas.mapRenderer().layerSet()
            #layers.append(layer.id())
            print " layer id :",layer.id()
            #print " nb layers :",len(layers)
            #self.canvas.mapRenderer().setLayerSet(layers) 
            canvas_layer = QgsMapCanvasLayer(layer)
            self.canvas.setLayerSet([canvas_layer])           
            self.canvas.zoomToFullExtent()
            #refreshMap()
            #self.canvas.emit(SIGNAL("mapCanvasRefreshed()"))
            #emit self.canvas.mapCanvasRefreshed()
        else:
            print "file ",path," doesnot exists!"
            
    def zoomIn(self):
        self.canvas.setMapTool(self.toolZoomIn)
    
    def zoomOut(self):
        self.canvas.setMapTool(self.toolZoomOut)
    
    def pan(self):
        self.canvas.setMapTool(self.toolPan)
                    
if __name__ == "__main__":
    
    # supply path to where is your qgis installed
    pathapp=u"F:/OSGEO4w64/apps/qgis"
    QgsApplication.setPrefixPath(pathapp, True)
    QgsApplication.initQgis()
    # creation de l'application
    app = QgsApplication([], True)
    #print QgsApplication.showSettings()
    #r = QgsProviderRegistry.instance()
    #print len(r.providerList())
    #for i in r.providerList():
    #    print i
    #ok=QLibrary(pathapp+u'/plugins/ogrprovider.dll').load()
    #print ok

    window = Window()
    window.loadLayer("E:/ETUDES_CAIRN/BV_MSSA/emissions_MSSA_rev1_sp.kml","myname")
    window.repaint()
    window.show()
    
    
    app.exec_()
    # delete main window
    window=None
    QgsApplication.exitQgis()