overlaying raster layer hides my vector layers in PyQGIS

Question

I loaded vector layers and rendered them without a problem but when I tried to add a raster layer as well the map suddenly only shows the raster image and my vector layers are missing.

Anything I can try to diagnose the issue here. I was following the routine steps in the PyQGIS 2.0 cookbook.

    import sys
    from PyQt4.QtCore import *
    from PyQt4.QtGui import *
    from qgis.core import *
    from qgis.gui import *
    import sys
    import os
    from mapui import Ui_MainWindow

    os.environ['QGISHOME'] = 'C:\\Program Files\\QGIS Brighton\\apps\\qgis'


    class ShapeViewer(QMainWindow, Ui_MainWindow):
    def __init__(self):
        QMainWindow.__init__(self)

        #Required by Qt4 to initialize the UI
        self.setupUi(self)

        #set the title for the app
        self.setWindowTitle("Map Viewer")

        #create the map canvas
        self.canvas = QgsMapCanvas()
        self.canvas.setCanvasColor(Qt.white)
        self.canvas.enableAntiAliasing(True)
        #self.canvas.useImageToRender(False)
        self.canvas.show()

        self.clickTool = QgsMapToolEmitPoint(self.canvas)

        self.layout = QVBoxLayout(self.QgsMapCanvas)
        self.layout.addWidget(self.canvas)

        layers = []

        uri = QgsDataSourceURI()
        #underlying map
        raster_layer = QgsRasterLayer("d:\\working\\hyp_lr\\hyp_lr\\hyp_lr.tif", 'geography layer')

        if not raster_layer.isValid():
            print "raster layer is invalid!"
            return

        QgsMapLayerRegistry.instance().addMapLayer(raster_layer)
        self.canvas.setExtent(raster_layer.extent())
        cl_raster = QgsMapCanvasLayer(raster_layer)

        layers.append(cl_raster)


        uri = QgsDataSourceURI()
        uri.setConnection("my_linux_box","5432","mydb","me","mypwd")
        uri.setDataSource('public','some_table','geom','')
        vector_layer = QgsVectorLayer(uri.uri(), 'Some Data', "postgres")

        if not vector_layer.isValid():
            print "Vector layer is invalid!"
            return

        QgsMapLayerRegistry.instance().addMapLayer(vector_layer)

        self.canvas.setExtent(vector_layer.extent())

        vector_canvas_layer = QgsMapCanvasLayer(vector_layer)
        layers.append(vector_canvas_layer)


        ####
        self.canvas.setLayerSet(layers)


        self.canvas.show()



def main(argv):
    #create Qt application
    app = QApplication(argv)

    #init qgis libs
    qgis_prefix = 'C:\\OSGEO4~1\\apps\\qgis'
    QgsApplication.setPrefixPath(qgis_prefix, True)
    QgsApplication.initQgis()

    #create the main window
    wnd = ShapeViewer()

    #Move the app window to upper left
    wnd.move(100, 100)
    wnd.show()

    #run!
    retval = app.exec_()

    #exit
    QgsApplication.exitQgis()
    sys.exit(retval)


if __name__=='__main__':
    main(sys.argv)

Answer 1

When you add the vector layer to the map, you need to put it on top of the raster layer.

So, instead of:

layers.append(vector_canvas_layer)

which puts the vector at the bottom, write this:

layers.insert(0, vector_canvas_layer)

which inserts the vector layer at the position 0 (at the top) of your layer stack.

You should now be able to visualize both your vector and raster data.