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I'm trying to grab the coordinates from a click. If I type this code (obtained from Getting coordinates from mouse click in QGIS 3 (python plugin)):

def display_point(pointTool):
    try:
        print(pointTool.x(), pointTool.y())
    except AttributeError:
        pass

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)
display_point(pointTool)

in the python console it works perfectly. But if I place it inside my plugin class it does not work, don't even get the cross mouse pointer and I have no idea why is not working:

...
    def display_point(self, pt, bt):
        try:
            print(pt.x(), pt.y(), bt)
        except AttributeError:
            print("No attribute")

def on_create_ignition_point(self):
    print("IN")
    canvas = self.iface.mapCanvas()
    pointTool = QgsMapToolEmitPoint(canvas)
    pointTool.canvasClicked.connect(self.display_point)
    canvas.setMapTool(pointTool)
    print('OUT')



...

the function on_create_ignition_point gets called from a toolbar button and the IN and OUT messages are printed. Also created a class like is explained in Getting coordinates of point on mouse click using PyQGIS with the same results.

Any hints on what I'm doing wrong?

PolyGeo
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Jaume Figueras
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    In a plugin, should create instance attributes for canvas: self.canvas = self.iface.mapCanvas() and pointTool: self.pointTool = QgsMapToolEmitPoint(self.canvas) in the __init__ method of the main plugin class. Then create the signal/slot connection in the initGui method: self.pointTool.canvasClicked.connect(self.display_point). Finally, in your on_create_ignition_point() method, just set the canvas map tool: self.canvas.setMapTool(self.pointTool). – Ben W Feb 28 '22 at 23:35
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    I answered a similar question here: https://gis.stackexchange.com/questions/403628/printing-message-with-map-canvas-coordinates-after-user-click-in-qgis-plugin Maybe you will find it useful. – Ben W Feb 28 '22 at 23:35
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    Thank you for your answers, moving the variables to instance attributes solved the problem. Of course letting the point tool be a local variable was not a good idea. – Jaume Figueras Mar 04 '22 at 12:59
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    Perhaps you could create an answer with your working code and explanation of the changes you made. It will help future readers of this question. – Matt Mar 04 '22 at 13:01

1 Answers1

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Following the comments provided did the trick. Moving the local variables to instance attributes solved the problem.

The final code is this:

        if not (self._pointTool is None):
            self._pointTool.canvasClicked.disconnect()
            del self._pointTool
            self._previousTool = None
            self._pointTool = None
        # Store the previous tool in use b the user
        canvas = self._iface.mapCanvas()
        self._previousTool = canvas.mapTool()
        # Set the tool and onClick callback
        self._pointTool = QgsMapToolEmitPoint(canvas)
        self._pointTool.canvasClicked.connect(self.on_point_callback)
        canvas.setMapTool(self._pointTool)
Jaume Figueras
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