I am trying to make a standalone app, to be able to select and download some spatial data that I keep around. I've read around and found I can do that with Qgis and Qt, so I grabbed some example code from the docs, and assigned it a shapefile to open.
And it wouldn't work, regardless of what I tried with PATH and PROJ_LIB. While I was trying to work out my issues with:
proj_create_from_database: Cannot find proj.db
proj_get_authorities_from_database: Cannot find proj.db
I finally found out, I can avoid that by using:
C:\Program Files\QGIS 3.16\bin>python-qgis-ltr.bat myApp.py
Now a window is shown for a split second, then it disappears and the program finishes, as cmd is ready for new inputs.
Here is the whole code:
import sys
sys.path.append(r"C:\Program Files\QGIS 3.16\apps\qgis-ltr\python")
import os
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = r'C:\Program Files\QGIS 3.16\apps\Qt5\plugins'
os.environ['PROJ_LIB '] = r'C:\Program Files\QGIS 3.16\share\proj'
os.environ['PYTHONPATH'] = r'C:\Program Files\QGIS 3.16\apps\Python37'
from qgis.PyQt.QtGui import (
QColor,
)
from qgis.PyQt.QtCore import Qt, QRectF
from qgis.core import (
QgsVectorLayer,
QgsPoint,
QgsPointXY,
QgsProject,
QgsGeometry,
QgsMapRendererJob,
)
from qgis.core import *
from qgis.gui import (
QgsMapCanvas,
QgsVertexMarker,
QgsMapCanvasItem,
QgsRubberBand,
QgsMapToolPan,
QgsMapToolZoom,
)
from qgis.PyQt.QtWidgets import QAction, QMainWindow
class MyWnd(QMainWindow):
def init(self, layer):
QMainWindow.init(self)
self.canvas = QgsMapCanvas()
self.canvas.setCanvasColor(Qt.white)
self.canvas.setExtent(layer.extent())
self.canvas.setLayers([layer])
self.setCentralWidget(self.canvas)
self.actionZoomIn = QAction("Zoom in", self)
self.actionZoomOut = QAction("Zoom out", self)
self.actionPan = QAction("Pan", self)
self.actionZoomIn.setCheckable(True)
self.actionZoomOut.setCheckable(True)
self.actionPan.setCheckable(True)
self.actionZoomIn.triggered.connect(self.zoomIn)
self.actionZoomOut.triggered.connect(self.zoomOut)
self.actionPan.triggered.connect(self.pan)
self.toolbar = self.addToolBar("Canvas actions")
self.toolbar.addAction(self.actionZoomIn)
self.toolbar.addAction(self.actionZoomOut)
self.toolbar.addAction(self.actionPan)
# create the map tools
self.toolPan = QgsMapToolPan(self.canvas)
self.toolPan.setAction(self.actionPan)
self.toolZoomIn = QgsMapToolZoom(self.canvas, False) # false = in
self.toolZoomIn.setAction(self.actionZoomIn)
self.toolZoomOut = QgsMapToolZoom(self.canvas, True) # true = out
self.toolZoomOut.setAction(self.actionZoomOut)
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)
qgs = QgsApplication([], True)
qgs.initQgis()
pathToShp = r"D:\Docs\myTestShape.shp"
inLayer = QgsVectorLayer(pathToShp, "myTestShape", "or")
w = MyWnd(inLayer)
w.show()
What do I need to do to see something displayed and pan around it?
