import 'package:flutter/material.dart'; Future<void> showErrorAlert(context, errorString, callback) { return showDialog<void>( context: context, builder: (BuildContext context) { return AlertDialog( title: Text('Authorization error'), content: Text(errorString), actions: <Widget>[ FlatButton( child: Text('Open Dashboard'), onPressed: () async { Navigator.of(context).pop(); callback(); }, ), ], ); }, ); }