creating new UI fragement
formatting
add interface that MainActivity can implement to listen for new items being added
adding a variable to store a reference to the parent activity that will implement the interface
moving the code that adds a new todo list item into a fragment
adding fragment that will contain the list of todo items
removing reference to text box now that it is contained on fragment
update activity so that it uses the new fragments we just created
in the activity, use fragment manager to get access to fragments we just created
changing the name of the startup activity
implement the listener by implementing an onNewItemAdded handler