Android Question Regex Pattern in B4XFloatTextField (B4XDialog Custom)

Sub Button1_Click
   Dim p As B4XView = xui.CreatePanel("")
   p.SetLayoutAnimated(0, 0, 0, 300dip, 200dip)
   p.LoadLayout("MyDialog")
   Dialog.PutAtTop = True
   Dim rs As ResumableSub = Dialog.ShowCustom(p, "OK", "", "CANCEL")
   txtFirstName.TextField.RequestFocus
   IsDialogValid(txtFirstName.Text, txtLastName.Text)
   Wait For (rs) Complete (Result As Int)
   Dialog.PutAtTop = False
   If Result = xui.DialogResponse_Positive Then
       Dialog.Show($"Hello ${txtFirstName.Text} ${txtLastName.Text}"$, "OK", "", "")
   End If
End Sub

Private Sub IsDialogValid (FirstName As String, LastName As String)
   Dim ok As B4XView = Dialog.GetButton(xui.DialogResponse_Positive)
   If FirstName.Length > 0 And LastName.Length > 0 Then
       ok.Enabled = True
   Else
       ok.Enabled = False
   End If
End Sub

Sub txtFirstName_TextChanged (Old As String, New As String)
   IsDialogValid(New, txtLastName.Text)
End Sub

Sub txtLastName_TextChanged (Old As String, New As String)
   IsDialogValid(txtFirstName.Text, New)
End Sub