Flutter 应用程序无法跳过老用户的介绍屏幕

Question

我是新来的颤振。我正在制作一个应用程序，它在第一次使用该应用程序时将电话号码作为第一个屏幕中的输入。从下一次开始，我希望应用程序跳过第一个屏幕并直接转到下一个屏幕。但我无法实现此功能。请帮助。谢谢。

import 'package:shared_preferences/shared_preferences.dart';

class PrefShare {
  String mob;
  bool isNew;

  Future<String> spNumberSetter(String no) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setString('phoneNumber', no);
  }

  Future<String> spNumberGetter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    mob = prefs.getString('phoneNumber');
  }

  Future<bool> spAppNew() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setBool('isLoggedIn', true);
  }

  Future<bool> spAppGetter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    isNew = prefs.getBool('isLoggedIn');
  }
}


//main
import 'package:emergency_messaging/button_screen.dart';
import 'package:flutter/material.dart';
import 'prefs.dart';

PrefShare prefShare = PrefShare();

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  prefShare.spAppGetter();
  bool status = prefShare.isNew ?? false;
  prefShare.spAppNew();
  runApp(
    MaterialApp(home: status == true ? ButtonScreen() : Home()),
  );
}

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    String phoneNo;
    return SafeArea(
      child: Scaffold(
        backgroundColor: Color(0xff9ad3bc),
        floatingActionButton: FloatingActionButton(
          backgroundColor: Colors.black,
          child: Icon(
            Icons.arrow_forward,
            color: Color(0xff9ad3bc),
          ),
          onPressed: () {
            showDialog(
              context: context,
              builder: (context) {
                return AlertDialog(
                  title: Text("Confirmation"),
                  content: SingleChildScrollView(
                    child: ListBody(
                      children: <Widget>[
                        Text("The phone number entered is: $phoneNo"),
                      ],
                    ),
                  ),
                  actions: <Widget>[
                    FlatButton(
                      child: Text("Cancel"),
                      onPressed: () {
                        Navigator.pop(context);
                      },
                    ),
                    FlatButton(
                      child: Text("Continue"),
                      onPressed: () {
                        prefShare.spNumberSetter(phoneNo);
                        Navigator.push(
                            context,
                            MaterialPageRoute(
                                builder: (context) => ButtonScreen()));
                      },
                    ),
                  ],
                );
              },
            );
          },
        ),
        body: Padding(
          padding: EdgeInsets.all(8.0),
          child: Column(
            children: [
              SizedBox(
                height: 150.0,
              ),
              TextField(
                  style: TextStyle(color:  Colors.black,),
                  decoration: InputDecoration(

                    hintText: "Your emergency contact number",
                    hintStyle: TextStyle(color:  Colors.black,),
                    enabledBorder: UnderlineInputBorder(
                      borderSide: BorderSide(color:  Colors.black,),
                    ),
                    focusedBorder: UnderlineInputBorder(
                      borderSide: BorderSide(color:  Colors.black,),
                    ),
                  ),
                  keyboardType: TextInputType.phone,
                  autofocus: true,
                  cursorColor: Colors.black,
                  onChanged: (text) {
                    phoneNo = text;
                  },
                ),

            ],
          ),
        ),
      ),
    );
  }
}

Answer 1

我认为你的问题来自这里：prefShare.spAppGetter();

由于 Future<bool> spAppGetter() async {...} 是一个返回未来的异步函数，您应该使用await 调用它，这样您就可以确保在调用bool status = prefShare.isNew ?? false; 之前spAppGetter 已经完成 为此，您也应该将主要功能标记为异步。你的主要功能看起来像这样：

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await prefShare.spAppGetter();
  bool status = prefShare.isNew ?? false;
  prefShare.spAppNew();
  runApp(
    MaterialApp(home: status == true ? ButtonScreen() : Home()),
  );
}

Answer 2

你没有使用getBool("isLoggedIn")的状态

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  prefShare.spAppGetter();// it will actually tell you that you if user logged in or not
  bool status = prefShare.isNew ?? false;
  prefShare.spAppNew(); // this should be where the user once logged in.
  runApp(
    MaterialApp(home: status == true ? ButtonScreen() : Home()),
  );
}

应该是这样的

void main() async{
  WidgetsFlutterBinding.ensureInitialized();
    bool status =await SharedPreferences.getInstance().getBool('isLoggedIn');
    runApp(
    MaterialApp(home: status == true ? ButtonScreen() : Home()),
  );
}

并在此处保存登录状态

  FlatButton(
                          child: Text("Continue"),
                          onPressed: () {
                            prefShare.spNumberSetter(phoneNo);
SharedPreferences.getInstance().setBool('isLoggedIn');
                            Navigator.push(
                                context,
                                MaterialPageRoute(
                                    builder: (context) => ButtonScreen()));
                          },
                        ),

你还应该研究命名约定