PyQGIS – Use Coordinates from Mouse Click for QgsPointXY

coordinatesfields-attributesgeometrypointpyqgis

I can not figure out how to input the coordinates through a mouse click instead of the code below. I am trying to create a temporary layer of a point from a mouse click. Everything seems to work except for that I can not figure the coordinates out.

from qgis.PyQt.QtCore import QVariant

vl = QgsVectorLayer("Point", "POI", "memory")    
pr = vl.dataProvider()
pr.addAttributes([QgsField("ID", QVariant.String)])
vl.updateFields() 
f = QgsFeature()
f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(10,10)))
f.setAttributes(["1"])

pr.addFeature(f)
vl.updateExtents() 
QgsProject.instance().addMapLayer(vl)

Best Answer

Combining lines in this link and your code, it looks as follows:

from qgis.gui import QgsMapToolEmitPoint
from qgis.PyQt.QtCore import QVariant

def display_point( pointTool ): 

    vl = QgsVectorLayer("Point", "POI", "memory")    
    pr = vl.dataProvider()
    pr.addAttributes([QgsField("ID", QVariant.String)])
    vl.updateFields() 
    f = QgsFeature()
    f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(pointTool[0],pointTool[1])))
    f.setAttributes(["1"])

    pr.addFeature(f)
    vl.updateExtents() 
    QgsProject.instance().addMapLayer(vl)

# a reference to our map canvas 
canvas = iface.mapCanvas() 

# this QGIS tool emits as QgsPoint after each click on the map canvas
pointTool = QgsMapToolEmitPoint(canvas)

pointTool.canvasClicked.connect( display_point )

canvas.setMapTool( pointTool )

After running it in Python Console of QGIS 3, it can be observed in following image, after 10 mouse clicks, there were produced 10 point layers as expected.

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PyQGIS – Programmatically Check for Mouse Click in PyQGIS

The best way to make a new tool like the Select Single Feature tool is to inherit from the QgsMapTool class. When your tool is active, which can be set using QgsMapCanvas::setMapTool, any keyboard or click events the canvas gets will be passed onto your custom tool.

Here is a basic QgsMapTool class

class PointTool(QgsMapTool):   
    def __init__(self, canvas):
        QgsMapTool.__init__(self, canvas)
        self.canvas = canvas    

    def canvasPressEvent(self, event):
        pass

    def canvasMoveEvent(self, event):
        x = event.pos().x()
        y = event.pos().y()

        point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

    def canvasReleaseEvent(self, event):
        #Get the click
        x = event.pos().x()
        y = event.pos().y()

        point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

    def activate(self):
        pass

    def deactivate(self):
        pass

    def isZoomTool(self):
        return False

    def isTransient(self):
        return False

    def isEditTool(self):
        return True

You can do what you need in canvasReleaseEvent, etc

To set this tool active you just do:

tool = PointTool(qgis.iface.mapCanvas())
qgis.iface.mapCanvas().setMapTool(tool)

[GIS] Making POINT from longitude/latitude coordinates in existing table using PostGIS

Maybe I'm not understanding, but you seem to be entering Longitude Latitude coordinates (-97, 21) in degrees,into a CRS that is UTM based, and uses meters. If you're declaring this as SRID 26918, then the long/lat values must be in that CRS. If the Long/Lat values are in degrees then you will need to create the geometry as ST_SetSRID(MakePoint(...),4326) then transform the layer to 26913. So, putting it all together, if you need to have the layer in 26913, but your longitude/latitude columns are in degrees, with CRS 4326, then

UPDATE sysinst.bio SET geom = ST_Transform(ST_SetSRID(ST_MakePoint(longitude, latitude), 4326),26913);

Best Answer

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PyQGIS – Programmatically Check for Mouse Click in PyQGIS

[GIS] Making POINT from longitude/latitude coordinates in existing table using PostGIS

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