An editable listview in Xamarin Forms

I need a list view which is bound to a collection and has an an "Add" button in the footer. When clicked, the button should add a new item to the list which contains an editable textbox. When the user has finished entering text the Listview item should become readonly (i.e. the textbox should be replaced with a label)

An example can be found on the "Budgets" screen of the Fudget application found in the Apple app store.