Sencha touch 2 segmented control check which button pressed

Sencha touch 2 segmented control check which button pressed

I have checked this out over the sencha touch examples that the items in
the segmented button can be handled programmatically. The issue that i am
facing currently is how to get the button that is pressed.
I need to store the index of the button that is pressed in my stores for
further references so that when i launch the screen again I am able to
select the buttons over the segmented control based on the selection.
I am handling the toggle event of the segmented button which takes three
arguments: - segmentedbutton - button that is pressed - pressed state.
I have access to the button when the event is generated but I am not able
to find out how to get the index of the button.
Can someone provide some light on this ?
Thanks J