I created the simple frame .UI file, compiled with pyuic4, and tried the ShapeViewer.py to load the shapefile "world_borders.shp". However, the map is always loaded in different random colors every time I rerun the python program. Why is this so? I tried loading the map in QGIS program & it loaded consistently with the same colors.
#! /usr/bin/env python
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from qgis.core import *
from qgis.gui import *
import sys, os
# Import our GUI.
from shapeviewer_gui import Ui_MainWindow
class ShapeViewer(QMainWindow, Ui_MainWindow):
def __init__(self):
QMainWindow.__init__(self)
# Required by Qt4 to initialize the UI.
self.setupUi(self)
self.layers = []
# Set the title for the app.
self.setWindowTitle("ShapeViewer")
# Create the map canvas.
self.canvas = QgsMapCanvas()
self.canvas.useImageToRender(False)
# Set the background color to white.
self.canvas.setCanvasColor(Qt.white)
self.canvas.enableAntiAliasing(True)
self.canvas.show()
# Lay our widgets out in the main window using a vertical box layout.
self.layout = QVBoxLayout(self.frame)
self.layout.addWidget(self.canvas)
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.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()
# Layout is set - open a layer.
# Add an OGR layer to the map.
self.Add_Map_Layer("qgis_data/world_borders.shp")
self.connect(actionZoomIn, SIGNAL("triggered()"), self.zoomIn)
self.connect(actionZoomOut, SIGNAL("triggered()"), self.zoomOut)
self.connect(actionPan, SIGNAL("triggered()"), self.pan)
def zoomIn(self):
self.canvas.setMapTool(self.toolZoomIn)
def zoomOut(self):
self.canvas.setMapTool(self.toolZoomOut)
def pan(self):
self.canvas.setMapTool(self.toolPan)
def Add_Map_Layer(self, mapFileName):
# Add the layer
if mapFileName == "":
layer = QgsVectorLayer()
else:
layer = QgsVectorLayer(os.path.abspath(mapFileName), mapFileName[mapFileName.rfind("/")+1:-4], "ogr")
if not layer.isValid():
print "Layer failed to load! :("
return
# Add layer to the registry
QgsMapLayerRegistry.instance().addMapLayer(layer);
# Set extent to the extent of our layer
self.canvas.setExtent(layer.extent())
# Set up the map canvas layer set
self.layers.append( QgsMapCanvasLayer(layer) )
self.canvas.setLayerSet(self.layers)
def main(argv):
# create Qt application
app = QApplication(argv)
# Environment variable QGISHOME must be set to the install directory
# before running the application
qgis_prefix = os.getenv("QGISHOME")
if qgis_prefix == None:
qgis_prefix = "/usr"
# Initialize qgis libraries
QgsApplication.setPrefixPath(qgis_prefix, True)
QgsApplication.initQgis()
# create 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)
