def populateLayerTree(self):
    myTree = self.dlg.ui.treeLayer
    myTree.headerItem().setText(0, 'Layer List')
    myDic = {}
    myGroups = self.iface.legendInterface().groups()
    for a in self.iface.legendInterface().groupLayerRelationship():
      # initialize values
      parentItem = None
      myId = a[0]

      # select an existing item, select the header item or create the item
      if myId in myDic:
        # if the item already exists in myDic, select it
        parentItem = myDic[myId]['item']
      elif myId == '':
        # if the id is empty string, this is a root layer, select the headerItem
        parentItem = myTree.headerItem()
      else:
        # else create the item and add it to the header item
        # add the item to the dictionary
        myDic[myId] = {'id' : myId}
        if myId in myGroups:
          # it's a group
          myDic[myId]['type'] = 'group'
        else:
          # it's a layer
          myDic[myId]['type'] = 'layer'
        parentItem = QTreeWidgetItem(['%s' % unicode(myId)])
        myTree.addTopLevelItem(parentItem)
        myDic[myId]['item'] = parentItem

      # loop through the children and add children to the parent item
      for b in a[1]:
        myDic[b] = {'id' : b}
        if b in myGroups:
          # it's a group
          myDic[b]['type'] = 'group'
        else:
          # it's a layer
          myDic[b]['type'] = 'layer'

        childItem = QTreeWidgetItem(['%s' % unicode(b)])
        if myId == '':
          myTree.addTopLevelItem(childItem)
        else:
          parentItem.addChild(childItem)
        myDic[b]['item'] = childItem