使用更改通知程序提供程序的提供程序未在另一个屏幕中显示更新状态

Question

im using provider and change notifier, the problem is when i change the state and notifiy listeners in the same file the user interface is updated, but when i try to access the same data from the model in another screen it still keeps the original or first version and not the updated version, the class in the other file is even using change notifier provider and a consumer just as the file with the modal class inside but is not changing the value, its only keeping the initial value, the second file only has changenotifierprovider and consumer, but it only displays the initial not the updated but the first file with the model class, and change notifier function is displaying the updated version in its widgets

And this is my second screen, which only displays the intial states even after they are updated in the frst screen

import 'package:flutter/material.dart';
import 'package:hotel_search/common/theme.dart';
import 'package:hotel_search/sliding_bottom_sheet_content.dart';
import 'package:hotel_search/home_page.dart';
import 'package:provider/provider.dart';

class BookScreen extends StatefulWidget {
  @override
  _BookScreenState createState() => _BookScreenState();
}

class _BookScreenState extends State<BookScreen> {
  @override
  void initState() {
    super.initState();

    /*Future.delayed(Duration(milliseconds: 1000)).then((v) {
      Navigator.pop(context);
    });*/
  }

  @override
  Widget build(BuildContext context) {
    final themeData = HotelConceptThemeProvider.get();
    return ChangeNotifierProvider<MyModel>(
        create: (context) => MyModel(),
        child: MaterialApp(
            home: Scaffold(
                backgroundColor: Colors.grey[50],
                appBar: AppBar(
                    leading: IconButton(
                      icon: Icon(Icons.arrow_back, color: Colors.black),
                      onPressed: () => Navigator.of(context).pop(),
                    ),
                    elevation: 0,
                    titleSpacing: 0,
                    backgroundColor: Colors.white,
                    title: Text(' ',
                        style: TextStyle(
                          color: Colors.black,
                          fontFamily: 'Montserrat',
                          fontSize: 20,
                        ))),
                body: SingleChildScrollView(
                    child: ConstrainedBox(
                  constraints: BoxConstraints(
                    minHeight: MediaQuery.of(context).size.height,
                  ),
                  child: Column(
                      mainAxisSize: MainAxisSize.min,
                      mainAxisAlignment: MainAxisAlignment.start,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: <Widget>[
                        SizedBox(
                          height: 40,
                        ),
                        Container(
                            width: MediaQuery.of(context).size.width - 100,
                            height: 100,
                            child: Image.asset(
                              "assets/images/brand.png",
                              width: 0,
                              height: 0,
                              fit: BoxFit.cover,
                            )),
                        Divider(
                          height: 25,
                          color: Colors.grey[300],
                        ),
                        Container(
                            padding:
                                EdgeInsets.only(left: 20, top: 20, bottom: 20),
                            width: MediaQuery.of(context).size.width,
                            child: Text('Review \nYour Booking',
                                style: TextStyle(
                                  color: Colors.black,
                                  fontFamily: 'Montserrat',
                                  fontSize: 30,
                                ))),
                        Divider(
                          height: 25,
                          color: Colors.grey[300],
                        ),
                        Container(
                            padding: EdgeInsets.only(left: 20, top: 20),
                            width: MediaQuery.of(context).size.width,
                            child: Text("HOTEL NAME",
                                style: TextStyle(
                                  fontFamily: 'Montserrat',
                                  fontSize: 20,
                                  fontWeight: FontWeight.w700,
                                ))),
                        Row(children: <Widget>[
                          Consumer<MyModel>(
                              builder: (context, myModel, children) {
                            return Container(
                                height: 100,
                                child: Column(
                                    mainAxisAlignment: MainAxisAlignment.start,
                                    children: <Widget>[
                                      Container(
                                          padding:
                                              EdgeInsets.only(left: 20, top: 5),
                                          width: 200,
                                          child: Text(
                                              myModel.datesChosen.toString(),
                                              style: TextStyle(
                                                fontSize: 13,
                                                fontFamily: 'Montserrat',
                                              ))),
                                      Container(
                                        padding:
                                            EdgeInsets.only(left: 20, top: 5),
                                        width: 200,
                                        child: Text(myModel.roomtype.toString(),
                                            style: TextStyle(
                                              fontSize: 13,
                                              fontFamily: 'Montserrat',
                                            )),
                                      ),
                                      Container(
                                          padding:
                                              EdgeInsets.only(left: 20, top: 5),
                                          width: 200,
                                          child: Text("CHECK IN AND OUT TIME",
                                              style: TextStyle(
                                                fontSize: 13,
                                                fontFamily: 'Montserrat',
                                              ))),
                                      Container(
                                          padding:
                                              EdgeInsets.only(left: 20, top: 5),
                                          width: 200,
                                          child: Text("TYPE OF ROOM CHOSEN",
                                              style: TextStyle(
                                                fontSize: 13,
                                                fontFamily: 'Montserrat',
                                              )))
                                    ]));
                          }),
                          Spacer(),
                          Container(
                              margin: EdgeInsets.only(right: 20),
                              width: 150,
                              height: 120,
                              decoration: BoxDecoration(
                                  image: DecorationImage(
                                      image: AssetImage("img/card.jpg"),
                                      fit: BoxFit.cover),
                                  color: Colors.grey[300],
                                  shape: BoxShape.rectangle,
                                  borderRadius: BorderRadius.circular(10),
                                  boxShadow: [
                                    BoxShadow(
                                      color: Colors.grey.withOpacity(0.2),
                                      spreadRadius: 2,
                                      blurRadius: 5,
                                      offset: Offset(
                                          0, 3), // changes position of shadow
                                    )
                                  ]))
                        ]),
                        SizedBox(height: 60),
                        Divider(
                          height: 25,
                          color: Colors.grey[300],
                        ),
                        SizedBox(height: 20),
                        Container(
                          color: Color(0xff008d4b),
                          height: 60,
                          width: MediaQuery.of(context).size.width - 50,
                          child: FlatButton(
                            onPressed: () {
                              /*...*/
                            },
                            child: Text(
                              "Book Now",
                              style: TextStyle(
                                color: Colors.white,
                                fontFamily: 'Montserrat',
                                fontSize: 20,
                              ),
                            ),
                          ),
                        )
                      ]),
                )))));
  }
}

this is the part of my first where i created my changenotifier, theres more but it was long so i just added this part, but all widgets here display the updated state

class MyModel with ChangeNotifier{



   String datesChosen = "Click here";
   String checkin;
   String checkout;
   String email;
   String name;
   String roomtype = "Click here";
   String phonenumber;
   String hotelname;



   void updateData1 (data){



           datesChosen = data;
           print(datesChosen);

           notifyListeners();





   }

    void updateData2 (data){



           roomtype = data;
           print(roomtype);

           notifyListeners();





   }

Answer 1

in your second screen you're using

ChangeNotifierProvider<MyModel>(
   create: (context) => MyModel(),
   ....
)

which means you're actually creating a new Model, not reusing the one of your first page (They're unrelated and changing one won't change the other), I don't know how you call the second screen so this is more speculative but you doul pass the model from the previous screen to the second and then use ChangeNotifierProvider<MyModel>.value() , that will register the same model and notify both pages when a change occurs

in the first screen

onTap: Navigator.of(context).push(
    MaterialPageRoute(
      builder: BookScreen(Provider.of<MyModel>(context, listen: false))
    )
);

now in the second screen

class BookScreen extends StatefulWidget {
  final MyModel model;

  BookScreen(this.model);


  @override
  _BookScreenState createState() => _BookScreenState();
}

class _BookScreenState extends State<BookScreen> {
  @override
  void initState() {
    super.initState();

    /*Future.delayed(Duration(milliseconds: 1000)).then((v) {
      Navigator.pop(context);
    });*/
  }

  @override
  Widget build(BuildContext context) {
    final themeData = HotelConceptThemeProvider.get();
    return ChangeNotifierProvider<MyModel>.value(
        value: widget.model,
        ....
    )

Obviously if you created the provider MyModel at the beginning of your app (above your first MaterialApp) you don't need all this logic and could simply use it everywhere