B4J Question treeview, get checked nodes

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("Layout1")
    MainForm.Show
    TreeView1.SetCheckBoxesMode
    For i = 1 To 10
        Dim tn As CheckboxTreeItem
        tn.Initialize("", i)
        TreeView1.Root.Children.Add(tn)
    Next
End Sub


Private Sub Button1_Click
    For Each tn As CheckboxTreeItem In TreeView1.Root.Children
        If tn.Checked Then
            Log(tn.Text)    
        End If
    Next
End Sub