Filter combobox to show only Points layers

Question

I am creating a plugin using QT Designer and QGIS 2.18. Using Plugin Builder along with examples I have been able to create a combo box that list all current layers in QGIS. I only want to list point layers. From hours of research I keep reading similar threads saying to use custom QT widgets like QgsMapLayerComboBox. But this is where I get confused.

Are these Qgs widgets added into QT Designer in some manner? Or in my script.py directly? Then I read one has to edit the ‘dialog_base.ui’ every time I make change in QT Designer? Can someone lead me on how to filter the combobox below to only view point layers?

Here is my code:

def run(self):
    """Run method that performs all the real work"""
    layers = self.iface.legendInterface().layers()
    layer_list = []
    for layer in layers:
        layer_list.append(layer.name())
    self.dlg.comboBox.addItems(layer_list)


    # show the dialog - this is needed
    self.dlg.show()
    # Run the dialog event loop
    result = self.dlg.exec_()
    # See if OK was pressed
    if result:
        # Do something useful here - delete the line containing pass and
        # substitute with your code.
        pass

Answer 1

I definitely recommend using the QGIS custom widgets. You should have a Qt Designer packaged with your QGIS installation which has these custom widgets available to drag and drop into a dialog like any other Qt widget.

The following is for Windows (I'm not sure about other operating systems).

Start typing Qt into the Windows search bar and select from the results-

Alternatively, you can start Designer with QGIS widgets from the batch file in the bin folder of your installation files:

Drag a QgsMapLayerComboBox into your plugin dialog. I suggest changing the object name to something unique to assist with accessing the correct widgets in your plugin.py file.

In my example I changed the object name to cb_point_layer, so this widget would be accessed with self.dlg.cb_point_layer. Note: A QgsMapLayerComboBox shows all layers loaded in the current project by default, so you don't need to add layer items to it like a regular combo box- you just need to add filters if you wish to limit the layers shown. So to show only point layers you would use:

self.dlg.cb_point_layer.setFilters(QgsMapLayerProxyModel.PointLayer)

Optionally, you can also show the CRS for each layer item in the combo box with:

self.dlg.cb_point_layer.setShowCrs(True)

Also, it is better to add this basic dialog logic to the initGui() method, rather than the run() method- especially if you are making any signal/slot connections. E.g.

def initGui(self):
    """Create the menu entries and toolbar icons inside the QGIS GUI."""

    icon_path = ':/plugins/my_plugin/icon.png'
    self.add_action(
        icon_path,
        text=self.tr(u'Do something...'),
        callback=self.run,
        parent=self.iface.mainWindow())
    self.dlg.cb_point_layer.setFilters(QgsMapLayerProxyModel.PointLayer)
    # optional
    self.dlg.cb_point_layer.setShowCrs(True)

Then, to access the layer selected in the map layer combo box, just use the currentLayer() method. For example, in the run() method:

def run(self):
    """Run method that performs all the real work"""
    # show the dialog
    self.dlg.show()
    # Run the dialog event loop
    result = self.dlg.exec_()
    # See if OK was pressed
    if result:
        # Do something useful here - delete the line containing pass and
        # substitute with your code.
        point_layer = self.dlg.cb_point_layer.currentLayer()
        # do something with point_layer