PyQGIS SIGNAL call weirdness

Question

I made a little plugin in QGIS, and I got some strange results. The program now mirrors the "Layers Panel". When I add or delete layers from the Panel the QListWidget module get the names of layers. I connected the function to the legendLayersAdded and to layersRemoved SIGNAL.

THE PROBLEM: The add part is ok, and if I remove ONE layer that's fine too. But if I remove multiple layers, the widget gets back the rest of layers' names multiple times (count of removed layers).

Community edit: For however many multiple layers are removed, the remaining layers appear in the list that many times. Ergo, if 3 layers are removed, and there is 1 remaining, that layer appears 3 times in the additional layer pane:

It's like the signal calls the function recursively!? I tried with the layerWasRemoved Signal and the result was the same I made a video of it because it is hard to explain.

[https://www.youtube.com/watch?v=NuLtANtlLtE&feature=youtu.be]

Here is the code:

def ablak(self):
layers = [] 
self.dockwidget.telepules_kezelo.clear()
layers = self.iface.legendInterface().layers()
print "Befor" # Befor layer list
print layers # Layer list "from Layers Panel"
print "After" # After layer list
i = 0 # Just a counter for debubing
lista = self.dockwidget.telepules_kezelo
for layer in layers:
    print layer.name()
    lista.addItem(layer.name())
    i = i+1
    print i # Counter for debuging
layers = []


QgsMapLayerRegistry.instance().legendLayersAdded.connect(self.ablak)

QgsMapLayerRegistry.instance().layersRemoved.connect(self.ablak)

I fade out the problem with transfer the self.dockwidget.telepules_kezelo.clear() line after the Print After line. And it's working fine, but I am really frustrated with it.

Answer 1

I think your function can be shortened down a bit as you have defined lists but not really using them (atleast not what you have shown).

The following function does the following whenever a layer(s) are added or removed (as suggested by @coneypylon):

• Clears the widget
• Only adds the layers currently loaded in the panel

(Tested on QGIS 2.18.2):

def ablak(self):
    self.dockwidget.telepules_kezelo.clear()
    for layer in QgsMapLayerRegistry.instance().mapLayers().values():            
        self.dockwidget.telepules_kezelo.addItem(layer.name())

QgsMapLayerRegistry.instance().legendLayersAdded.connect(self.ablak)
QgsMapLayerRegistry.instance().layersRemoved.connect(self.ablak)