Note that this tutorial was not updated yet with the changes regarding the Control keyword.
As of v6.90 it is recommended to not use it and instead use the new set of keywords that match the control type.
For example:
B4X:
Sub App_Start
AddForm("form1", "")
Form1.Color = cGray
Form1.Show
For i = 1 To 5
AddTextBox("form1", "t" & i, 20, 45 * i, 90, 40, "")
TextBox("t" & i).Text = "I'm Textbox t" & i 'instead of Control("t" & i, TextBox).Text = ...
Next
End Sub