Example of setting the focus on the 6th item which is an item made of a B4XFloatTextField.
B4X:
Dim sf As Object = p.ShowDialog(CreateMap(), "OK", "CANCEL")
Sleep(0)
Dim tf As B4XFloatTextField = p.CustomListView1.GetPanel(5).GetView(0).Tag
tf.TextField.RequestFocus
Wait For (sf) Complete (Result As Int)