The Accordion container (added in B4J v5.0) is a container similar to TabPane. It holds TitledPanes. These are panes with titles.
Using the accordion is quite simple. Add the Accordion node with the designer and create a layout file for each of the TitledPanes.
B4X:
Sub AppStart (Form1 As Form, Args() As String)
MainForm = Form1
MainForm.RootPane.LoadLayout("Main")
Accordion1.LoadLayout("Pane1", "Pane 1")
Accordion1.LoadLayout("Pane2", "Pane 2")
Accordion1.LoadLayout("Pane3", "Pane 3")
MainForm.Show
End Sub
It is recommended to use anchors in the layouts so the layout will be resized automatically based on the available size.