如何根据打开应用程序时收到的数据从一个页面转到另一个页面答案

【问题标题】：How to go from one page to another depending on the data they receive when opening the app如何根据打开应用程序时收到的数据从一个页面转到另一个页面
【发布时间】：2022-01-09 05:55:02
【问题描述】：

我正在尝试制作一个具有三种类型用户的应用程序：学生、教师和家长，我所做的是在登录时使用 shared_preferences 保存用户令牌的 ID，我希望它在输入时搜索数据库应用程序，根据用户类型，转到相应页面

目前我正在尝试这个

import 'package:app_plantel/padres_page.dart';
import 'package:app_plantel/profesores_page.dart';
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {

  Widget build(BuildContext context) {
    isLogged(context);
    return new Scaffold(
      body: Center(
        child: Icon(
          Icons.beach_access,
        ),
      ),
    );
  }
}

Future<String> _returnValue() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  final token = await prefs.getString("token");
  return token;
}

Future isLogged(context) async {

  await FirebaseFirestore.instance
    .collection('Padres')
    .doc(_returnValue().toString())
    .get()
    .then((DocumentSnapshot documentSnapshot) async {
      if (documentSnapshot.exists) {
        Navigator.of(context).push(MaterialPageRoute(builder: (context)=> PadresPage()));
      } else {
        await FirebaseFirestore.instance
        .collection('Alumnos')
        .doc(_returnValue().toString())
        .get()
        .then((DocumentSnapshot documentSnapshot) async {
          if (documentSnapshot.exists) {
            Navigator.of(context).push(MaterialPageRoute(builder: (context)=>  AlumnosPage()));
          } else {
            await FirebaseFirestore.instance
            .collection('Profesores')
            .doc(_returnValue().toString())
            .get()
            .then((DocumentSnapshot documentSnapshot) async {
              if (documentSnapshot.exists) {
                Navigator.of(context).push(MaterialPageRoute(builder: (context)=> ProfesoresPage()));
              } else {
                Navigator.of(context).push(MaterialPageRoute(builder: (context)=> LoginPage()));
              }
            });
          }
        });
      }
    });
}

但它给我带来了很多错误：

E/flutter (13461): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Navigator operation requested with a context that does not include a Navigator.
E/flutter (13461): The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.
E/flutter (13461): #0      Navigator.of.<anonymous closure> (package:flutter/src/widgets/navigator.dart:2553:9)
E/flutter (13461): #1      Navigator.of (package:flutter/src/widgets/navigator.dart:2560:6)
E/flutter (13461): #2      isLogged.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:app_plantel/main.dart:53:27)
E/flutter (13461): #3      isLogged.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:app_plantel/main.dart:49:19)
E/flutter (13461): #4      _rootRunUnary (dart:async/zone.dart:1436:47)
E/flutter (13461): #5      _CustomZone.runUnary (dart:async/zone.dart:1335:19)
E/flutter (13461): <asynchronous suspension>
E/flutter (13461): #6      isLogged.<anonymous closure>.<anonymous closure> (package:app_plantel/main.dart:45:13)
E/flutter (13461): <asynchronous suspension>
E/flutter (13461): #7      isLogged.<anonymous closure> (package:app_plantel/main.dart:37:9)
E/flutter (13461): <asynchronous suspension>
E/flutter (13461): #8      isLogged (package:app_plantel/main.dart:29:3)
E/flutter (13461): <asynchronous suspension>
E/flutter (13461):

我想知道如何解决它或他们建议能够做到的其他方法

【问题讨论】：

标签： firebase flutter

【解决方案1】：

抛出异常是因为您的Scaffold 上方没有MaterialApp 或CupertinoApp 小部件，并且导航需要它。像这样的：

return const MaterialApp(
  home: Scaffold(
    body: Center(
      child: Icon(
        Icons.beach_access,
      ),
    ),
  )
);

此外，您的isLogged 函数是async，但您不能在build 方法中等待它。考虑使用FutureBuilder 等待数据库响应，然后再开始构建主小部件。

【讨论】：

【解决方案2】：

你传入 isLogged 方法的上下文没有被导航器包裹。可以设置一个全局变量final _navKey = GlobalKey<NavigatorState>(); 然后用 Material 应用包裹你的 UI 并设置 Material 应用导航键

const MaterialApp(
  home: Scaffold(
    body: Center(
      child: Icon(
        Icons.beach_access,
      ),
    ),
  ),
navigatorKey: _navKey
);

最后使用key检索导航器上下文并在调用导航器时使用_navKey.currentState?.context

【讨论】：