我正在尝试通过路线从一个屏幕导航到另一个屏幕。当我点击页面上的按钮以移动到所提供的路线时，我得到了错误

I/flutter ( 8790): Another exception was thrown: There are multiple heroes that share the same tag within a subtree.

这是代码：

路线：

 <String, WidgetBuilder>{
    '/first':(BuildContext context) =>NavigatorOne() ,
    '/second':(BuildContext context) =>NavigatorTwo(),
    '/third':(BuildContext context) =>NavigatorThree(),

  },

Navigator.of(context).pushNamed('/first');
Navigator.of(context).pushNamed('/second');
Navigator.of(context).pushNamed('/third');

class NavigatorOne extends StatefulWidget {
  @override
  _NavigatorOneState createState() =>  _NavigatorOneState();
}

class _NavigatorOneState extends State<NavigatorOne> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(

      appBar: AppBar(),
      body: Container(
      color: Colors.green,
      child: RaisedButton(child: Text(' one 1'),onPressed: (){
        Navigator.of(context).pushNamed('/second');
      },),
    ),
    ); 
  }
}

错误：

══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════ I/flutter (21786): The following assertion was thrown during a scheduler callback: I/flutter (21786): There are multiple heroes that share the same tag within a subtree. I/flutter (21786): Within each subtree for which heroes are to be animated (typically a PageRoute subtree), each Hero I/flutter (21786): must have a unique non-null tag. I/flutter (21786): In this case, multiple heroes had the following tag: <default FloatingActionButton tag>

我该如何解决？