refresh indicator flutter

final GlobalKey<RefreshIndicatorState> _refreshIndicatorKey =
      GlobalKey<RefreshIndicatorState>();

body: RefreshIndicator(
        key: _refreshIndicatorKey,
        color: Colors.white,
        backgroundColor: Colors.blue,
        strokeWidth: 4.0,
        onRefresh: () async {
          // Replace this delay with the code to be executed during refresh
          // and return a Future when code finishs execution.
          return Future<void>.delayed(const Duration(seconds: 3));
        },
        // Pull from top to show refresh indicator.
        child: ListView.builder(
          itemCount: 25,
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              title: Text('Item $index'),
            );
          },
        ),
      ),

Navigator.pushAndRemoveUntil(
  context,
  MaterialPageRoute(builder: (context) => MainPage()),
  (Route<dynamic> route) => false,
);