WARNING: This is a demo app for a library project!

RefreshActionBarItem is an action bar item that implements this common pattern:

* Initially it shows a refresh button.
* If the button is clicked, a background operation begins and the button turns into a progress indicator.
* When the background operation ends, the button is restored to its initial state.

The progress bar shows a magnitude which represents how far the operation has proceeded. The progress bar can also be made indeterminate, just like the built-in ProgressBar.

It is possible to add a small badge to the action item. This tells the user that there is new data available.

The demo sample is a showcase of the functionality of the library.