Using only Selected Layer in mMapLayerComboBox

Question

I am building a plugin and so far I have tried simplifying the tasks. But my greatest challenge is making sure that the selected layer in the "mMapLayerComboBox" is what is exactly used in the operation shown below:

def run(self):
 mains = self.dlg.mMapLayerComboBox.currentLayer() ### vector layer
 laterals = self.dlg.mMapLayerComboBox_2.currentLayer() ### vector layer
 ovalay = self.dlg.mMapLayerComboBox_3.currentLayer() ### Raster layer
 for layer in checkedLayers:
 if layer.type() == QgsMapLayer.VectorLayer and self.dlg.checkBox_3.isChecked():
 # get extension about the raster
 filename, file_extension = os.path.splitext(layer.source())
 output1 = self.folderName + "/Profiles/m-length_" + layer.name() + ".shp"
 processing.run("qgis:exportaddgeometrycolumns", {"INPUT": mains, "CALC_METHOD": 0, "OUTPUT": output1})

In the "INPUT", I had specified the layer to use. However, while the task works, the main problem is that the task executes for all loaded vector layers in QGIS, even if I have a basemap like from google satellite it just tries to run the task on all available vector layers instead of the one I specified as:

 mains = self.dlg.mMapLayerComboBox.currentLayer() ### vector layer 

What I get as an output is a result for all the loaded layers including the specified layer in the "mMapLayerComboBox". I just want one output and not for all loaded vector or raster layers as the case may be.

How do I resolve this problem when using "mMapLayerComboBox" from QGIS built-in custom widget?

I want my task to only perform operations on the selected layer, that's all.

• Beginner: @PolyGeo, can you assist me, please. I really need help here.
• PolyGeo: Sorry @Beginner. I'm not a potential answerer of your question but I just added a tag for PyQGIS which should help it reach the filters of some of our volunteers who may be.

Answer 1

layers = QgsProject.instance().layerTreeRoot().children()
layerindex = self.dlg.mMapLayerComboBox.currentIndex()
layer = layers[layerindex]
print(layer)

Python Console: <qgis._core.QgsLayerTreeLayer object at 0x000001DD6DD8FD38

I did like this and one layer object was printed on python console.

• Pierrick Rambaud: Can you provide more written information on what you were trying to achieve ?
• Matt: The index of the QgsMapLayerComboBox may not necessarily match the index in the QgsLayerTree.