【Flutter】孫Widgetに渡したVoidCallback実行時にNoSuchMethodErrorが発生

Question

#実現したいこと
親ウィジェットから関数を渡していって子WidgetのRaisedButtonのonPressed部分で呼び出したいです。

#環境
Flutter 1.17.4
Dart 2.8.6
VSCode 1.46.1
macOS Catalina 10.15.5

#エラー内容

ビルド、実行はできますが、RaisedButtonを押した時にDEBUG CONSOLE内で以下のエラーが表示され、本来呼び出したい関数が呼び出されない。

═══════ Exception caught by gesture ═══════════════════════════════════════════
The following NoSuchMethodError was thrown while handling a gesture:
The method 'call' was called on null.
Receiver: null
Tried calling: call()

When the exception was thrown, this was the stack
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:53:5)
#1      _MemberPageState.build.<anonymous closure> 
package:day_log/main.dart:74
#2      HomeView.build.<anonymous closure> 
package:day_log/home.dart:42
#3      _InkResponseState._handleTap 
package:flutter/…/material/ink_well.dart:779
#4      _InkResponseState.build.<anonymous closure> 
package:flutter/…/material/ink_well.dart:862
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#c42bd
    debugOwner: GestureDetector
    state: possible
    won arena
    finalPosition: Offset(207.0, 456.0)
    finalLocalPosition: Offset(45.5, 17.5)
    button: 1
    sent tap down
════════════════════════════════════════════════════════════════════════════════

#コード
main関数はこちらです。

import 'package:flutter/material.dart';
import 'home.dart';
import 'Login.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example',
      theme: ThemeData.dark(),
      home: MemberPage(),
    );
  }
}

enum AuthStatus {
  nonSignedIn,
  signedIn,
}

class RootPage extends StatefulWidget {
  @override
  _RootPageState createState() => _RootPageState();
}

class _RootPageState extends State<RootPage> {
  AuthStatus authStatus = AuthStatus.nonSignedIn;

  void _signedIn() {
    setState(() {
      authStatus = AuthStatus.signedIn;
    });
  }

  void _signedOut() {　　　　　　//呼び出したい関数はこれです
    print(authStatus);
    setState(() {
      authStatus = AuthStatus.nonSignedIn;
    });
    print('authStatus is :');
    print(authStatus);
  }

  @override
  Widget build(BuildContext context) {
    switch (authStatus) {
      case AuthStatus.nonSignedIn:
        return LoginPage(onSignIn: _signedIn);
      case AuthStatus.signedIn:
        return MemberPage(signedOut: _signedOut);   //ここでMemberPage widgetに渡しています
      default:
        return null;
    }
  }
}

class MemberPage extends StatefulWidget {
  MemberPage({this.signedOut});
  final VoidCallback signedOut;
  @override
  _MemberPageState createState() => _MemberPageState();
}

class _MemberPageState extends State<MemberPage> {
  int _selectedPage = 0;

  @override
  Widget build(BuildContext context) {
    final _pageOptions = [
      HomeView(signedOut: widget.signedOut),   //ここでさらにHomeView widgetに渡しています
      Center(child: Text('Search')),
      Center(child: Text('Featured')),
      Center(child: Text('Setting')),
    ];
    return Scaffold(
      body: _pageOptions[_selectedPage],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _selectedPage,
        onTap: (int index) {
          setState(() {
            _selectedPage = index;
          });
        },
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            title: Text('Home'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            title: Text('Search'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.featured_play_list),
            title: Text('Featured'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.settings),
            title: Text('Setting'),
          ),
        ]
      ),
    );
  }
}

HomeViewwidgetのRaisedButtonから_signedOut関数を呼び出したいです。
HomeViewwidgetはこちらです。

import 'package:flutter/material.dart';

class HomeView extends StatelessWidget {
  HomeView({this.signedOut});
  final VoidCallback signedOut;

  @override
  Widget build(BuildContext context) {
    final width = MediaQuery.of(context).size.width;
    return Center(　　　　　　　　　　　　　　　　　　　　//↓でVoidCallbackを実行
      child: RaisedButton(child: Text('Sign Out'), onPressed: () => signedOut()), 
    );
  }
}

もしよろしければお力添えをお願い致します。

Answer 1

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example',
      theme: ThemeData.dark(),
      home: MemberPage(),
    );
  }
}

上記で home: MemberPage() としていますが、home: RootPage() ではないでしょうか。

Comments

[toshi_ki]

た、確かに…
直したら上手く行きました、単純なミスでお恥ずかしいです。。

ありがとうございました！