How to programmatically create nested layer groups?

Question

Using PyQGIS via the QGIS 2.4.0 Python console and the editor, I can create parallel groups for storing some layers with:

MyFirstGroup = iface.legendInterface().addGroup('Group No. 1')
MySecondGroup = iface.legendInterface().addGroup('Group No. 2')

The variables MyFirstGroup and MySecondGroup will store the GroupIDs (apparently 1 & 2). But how can I create the groups in a nested way so that MySecondGroup is a sub-group of MyFirstGroup?

Looking at the API docs, I find the addGroup function twice - one time expecting the parent group with a QTreeWidgetItem and one time via a int parentIndex.

When using the latter form as

MySecondGroup = iface.legendInterface().addGroup('Group No. 2', parentIndex = 1)

then I get a TypeError: QgsLegendInterface.addGroup(QString, bool expand=True, QTreeWidgetItem parent=None): 'parentIndex' is not a valid keyword argument

When only using

MySecondGroup = iface.legendInterface().addGroup('Group No. 2', 1)

or

MySecondGroup = iface.legendInterface().addGroup('Group No. 2', MyFirstGroup)

then groups are not created nested but in parallel.

What is the correct way to achieve this or where do I get the corresponding QTreeWidgetItem object for MyFirstGroup from?

Answer 1

You may use the addGroup function like this:

MyFirstGroup = iface.legendInterface().addGroup('Group No. 1')
MySecondGroup = iface.legendInterface().addGroup('Group No. 2', true, MyFirstGroup)

Answer 2

Legend interface has been refactored since 2.4 version. A detailed description how to add nodes, groups and subgroups can be found here:

http://www.lutraconsulting.co.uk/blog/2014/07/06/qgis-layer-tree-api-part-1/

and here

http://www.lutraconsulting.co.uk/blog/2014/07/25/qgis-layer-tree-api-part-2/

regards