Named route navigation error: type 'MaterialPageRoute<dynamic>' is not a subtype of type 'Route<String>'

Question

I'm trying to navigate to another page using a named route:

... RaisedButton(             child: Text('Get image'),             onPressed: () => Navigator.pushNamed<String>(                 context, '/second'),... 

but get the error

> I/flutter (12439): ══╡ EXCEPTION CAUGHT BY GESTURE > ╞═══════════════════════════════════════════════════════════════════ >     I/flutter (12439): The following assertion was thrown while handling a gesture: >     I/flutter (12439): type 'MaterialPageRoute<dynamic>' is not a subtype of type 'Route<String>' >     I/flutter (12439): Either the assertion indicates an error in the framework itself, or we should provide substantially >     I/flutter (12439): more information in this error message to help you determine and fix the underlying cause. >     I/flutter (12439): In either case, please report this assertion by filing a bug on GitHub: >     I/flutter (12439):   https://github.com/flutter/flutter/issues/new?template=BUG.md >     I/flutter (12439): When the exception was thrown, this was the stack: >     I/flutter (12439): #0      NavigatorState._routeNamed package:flutter/…/widgets/navigator.dart:1426 >     I/flutter (12439): #1      NavigatorState.pushNamed package:flutter/…/widgets/navigator.dart:1473 >     I/flutter (12439): #2      Navigator.pushNamed package:flutter/…/widgets/navigator.dart:740 >     I/flutter (12439): #3      _CompleterState.build.<anonymous closure> package:my_package/completer.dart:205 

The route is defined in the homepage:

class MyApp extends StatelessWidget {   // This widget is the root of your application.   @override   Widget build(BuildContext context) {     return MaterialApp(       title: 'XXXX',       theme: ThemeData(         primarySwatch: Colors.blue,       ),       home: Completer(),       routes: {         '/second': (BuildContext context) => SecondPage(),       },       onUnknownRoute: (RouteSettings settings) {         return MaterialPageRoute(           builder: (BuildContext context) => Completer(),         );       },     );   } } 

I couldn't find anything on this error message, so I seem to have generated an error that no-one else has seen before.

I'm slowly hacking away at the code to simplify it to the bare minimum, to work out what I've done wrong, but any pointers would be appreciated.

Answer 1

Blindingly obvious in hindsight.

I had added the String type-hint in Navigator.pushNamed<String>() as I thought I could receive a typed value back from the call. Removing that and receiving it into a var solved the problem.

Leaving this up for anyone else who gets themselves into the same state.