- A widget that supports the Material "swipe to refresh" idiom.
- Contains the state for a RefreshIndicator. This class can be used to programmatically show the refresh indicator, see the show method.
- Used to configure how RefreshIndicator can be triggered.
- The signature for a function that's called when the user has dragged a RefreshIndicator far enough to demonstrate that they want the app to refresh. The returned Future must complete when the refresh operation is finished.