1.
100% of the public methods in XUI Views are cross platform.
2. As I don't like to limit developers, most of the internal
fields are also exposed. Once you access an internal field, not everything is cross platform.
3. The XUI Views example fills a B4XComboBox and it obviously does it with the only relevant public method, which is SetItems.
It should be clear that the main feature of a cross platform combobox doesn't require such code:
#IF B4A
PortNumCmbo.cmbBox.Add(MP.DCUTs.smgr.Get("PortNum"))
#ELSE IF B4J
PortNumCmbo.cmbBox.Items.Add(MP.DCUTs.smgr.Get("PortNum"))
#Else
PortNumCmbo.????
#End If
If you start writing such code then stop and look again in the available methods. This is of course not the correct way to do it.