页面更改时颤动中消失的数据答案

【问题标题】：disappearing data in flutter on page change页面更改时颤动中消失的数据
【发布时间】：2021-04-05 19:06:22
【问题描述】：

我启动了 Flutter 应用程序来学习 API 功能，但我遇到了这个问题，即当我更改页面并返回上一页时，我正在显示的数据在所有页面上都变为空。我不知道这背后的原因。

下面是它的运行图像-：

下面是我从一页获取数据到主页并显示它的代码。并在页面更改时消失-：


import 'package:education/LogIn_SignUp/Log_In.dart';
import 'package:education/Screens/Profile_Screen.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'About_Scree.dart';
import 'Change_Password.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:async';






class homeView extends StatefulWidget{

  var user_id;
  var user_name;
  var mobile_number;
  var user_address;
  var user_Email;
  var coaching_id;
  var coaching_name;
  var coaching_address;
  var primary_no;
  var altnumber;
  var coaching_email;



  homeView({
    this.user_id,this.user_name,this.mobile_number,this.user_address,this.coaching_id,this.coaching_name,
    this.coaching_address,this.primary_no,this.altnumber,this.coaching_email,this.user_Email
});

  @override
  State<StatefulWidget> createState() => homeViewState();
}



class homeViewState extends State<homeView> {


  TextEditingController editingController = TextEditingController();

  var showItemList = List<String>();
  int count = 10;




  var userid, username, mobilenumber, useraddress, userEmail, coachingid, coachingname, coachingaddress;
  var primaryno, alt_number, coachingemail;

  void setdata(){
    setState(() {
      userid = widget.user_id;
      username = widget.user_name;
      mobilenumber = widget.mobile_number;
      useraddress = widget.user_address;
      userEmail = widget.user_Email;
      coachingid = widget.coaching_id;
      coachingname = widget.coaching_name;
      coachingaddress = widget.coaching_address;
    });
  }



  @override
  void initState(){
    // showItemList.addAll(initList);
    // getData();
    setdata();
    super.initState();
  }


  @override
  void dispose() {
    editingController.dispose();
    super.dispose();
  }

  /// -----------------------------------------------------------------------------------------------------------------------------
  ///                                           Main Build Function for the class.
  /// -----------------------------------------------------------------------------------------------------------------------------


  @override
  Widget build(BuildContext context) {

    return SafeArea(
      child: Scaffold(
        appBar: PreferredSize(
          preferredSize: Size.fromHeight(90.0),
          child: AppBar(
            title: Padding(
              padding: const EdgeInsets.only(top: 20),
              child: Text(
                '$coachingname',//'${widget.coaching_name}',
                style: TextStyle(
                  fontSize: 25.0,
                  letterSpacing: 4.5,
                  fontFamily: 'Sarif',
                  fontWeight: FontWeight.w300,
                  color: Colors.white,
                ),
              ),
            ),
            backgroundColor: Colors.deepPurpleAccent,
            centerTitle: true,
            actions: <Widget>[
              Column(
                children: [
                  InkWell(
                    child: new IconButton(
                        icon: Padding(
                          padding: const EdgeInsets.only(top: 20),
                          child: Icon(Icons.exit_to_app),
                        ),
                        onPressed:(){
                          Navigator.pushReplacement(context, MaterialPageRoute(
                            builder: (context) => LoginPage(),
                          ));
                        }
                    ),
                    onTap: (){
                      Navigator.pushReplacement(context, MaterialPageRoute(
                        builder: (context) => LoginPage()
                      ));
                    },
                  ),
                ],
              ),
            ],
          ),
        ),
        drawer: Drawer(
          child: Container(
            padding: EdgeInsets.all(10),
            child: ListView(
              children: <Widget>[

                Container(
                  height: 180,
                  decoration: BoxDecoration(
                    gradient: LinearGradient(colors: [
                      Colors.purple.shade300,
                      Colors.deepPurpleAccent.shade200,
                    ]),
                  ),
                  child: Column(
                    children: [

                      Padding(
                        padding: const EdgeInsets.only(top: 45.0, bottom: 10),
                        child: Card(
                            shape: RoundedRectangleBorder(
                              borderRadius: BorderRadius.circular(55),
                            ),
                            color: Colors.blue,
                            child: Padding(
                              padding: const EdgeInsets.all(10.0),
                              child: Icon(Icons.perm_identity_outlined, color: Colors.white,size: 30),
                            )
                        ),
                      ),

                      Text(
                        '$username',//'${widget.user_name}',
                        style: TextStyle(
                          color: Colors.white,
                          fontSize: 24,
                          letterSpacing: 2.5,
                        ),
                      ),


                    ],
                  ),
                ),


                ListTile(
                  title: Text('Profile',
                    style: TextStyle(
                    fontSize: 17,
                    fontWeight: FontWeight.w400,
                    letterSpacing: 1.5,
                  ),
                  ),
                  leading: Icon(Icons.person_pin, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){
                    Navigator.pushReplacement(context, MaterialPageRoute(
                      builder: (context) => ProfilePage(
                        user_id: userid, user_name:username, mobile_number:mobilenumber, user_address:useraddress,
                        user_Email: userEmail,
                      )
                    ));
                  },
                ),

                ListTile(
                  title: Text('Change Password',
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w400,
                      letterSpacing: 1.5,
                    ),
                  ),
                  leading: Icon(Icons.security, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){
                    Navigator.pushReplacement(context, MaterialPageRoute(
                      builder: (context) => ChangePassword()
                    ));
                  },
                ),

                ListTile(
                  title: Text('About',
                    style: TextStyle(
                    fontSize: 17,
                    fontWeight: FontWeight.w400,
                    letterSpacing: 1.5,
                  ),
                ),
                  leading: Icon(Icons.info_outline, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){
                    Navigator.pushReplacement(context, MaterialPageRoute(
                      builder: (context) => AboutScreen(
                        coaching_id:coachingid, coaching_name:coachingname, coaching_address:coachingaddress,
                        primary_no:primaryno, altnumber:alt_number, coaching_email:coachingemail
                      )//coaching details
                    ));
                  },
                ),

                ListTile(
                  title: Text(
                    'Rate',
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w400,
                      letterSpacing: 1.5,
                    ),
                  ),
                  leading: Icon(Icons.star_border_outlined, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){

                  },
                ),


                Divider(
                  color: Colors.red,
                  thickness: 1,
                ),


                SizedBox(height: 10,),

                Text(
                  'Contact Us',
                  style: TextStyle(
                    fontSize: 20,
                    color: Colors.grey[800],
                    letterSpacing: 1.5,
                    fontWeight: FontWeight.w500,
                  ),
                ),

                SizedBox(height: 10,),

                ListTile(
                  title: Text('Share',
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w400,
                      letterSpacing: 1.5,
                    ),
                  ),
                  leading: Icon(Icons.share, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){

                  },
                ),

                ListTile(
                  title: Text('Privacy Policy',
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w400,
                      letterSpacing: 1.5,
                    ),
                  ),
                  leading: Icon(Icons.privacy_tip, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){

                  },
                ),

                ListTile(
                  title: Text(
                    'LogOut',
                    style: TextStyle(
                      fontSize: 17,
                      fontWeight: FontWeight.w400,
                      letterSpacing: 1.5,
                    ),
                  ),
                  leading: Icon(Icons.logout, color: Colors.blue,),
                  selectedTileColor: Colors.blue,
                  onTap: (){
                    Navigator.pushReplacement(context, MaterialPageRoute(
                      builder: (context) => LoginPage()
                    ));

                  },
                ),



              ],
            ),
          ),
        ),
        body: Container(),
      ),
    );
  }
}

我传递给这个页面的数据如下 -:

I/flutter ( 4512): {address: jaipur, jaipur, alt_number: 9865358577, coach_address: Gautam Budha nagar, noida, coach_id: 2, coach_name: SSG Coaching, coaching_email: SSG@gmail.com, mobile_number: 9999999999, primary_no: 9898557898, res: success, user_id: 3, user_mail: s@gmail.com, user_name: sagar, user_pass: sagar123}

请帮忙，因为我无法追踪错误或找到任何解决方案。

【问题讨论】：

表示您想假设您从 MainPage 转到 homeView 页面然后显示数据，但是当您从 homeView 转到另一个页面并返回到另一个页面时，数据显示不正确？
是的，每当我更改页面时，数据就会消失
是的，因为您通过构造函数仅从一页发送数据。所以这个数据消失了

标签： api flutter flutter-layout

【解决方案1】：

这是因为您使用的是 Navigator.pushReplacement 而不是 Navigator.push。当您使用 pushReplacement 时，当前路由会被新路由覆盖。

所以用这个：

Navigator.push(context, MaterialPageRoute(
                      builder: (context) => ProfilePage(
                        user_id: userid, user_name:username, mobile_number:mobilenumber, user_address:useraddress,
                        user_Email: userEmail,
                      )
                    ));

在 ProfilePage 中，使用

Navigator.pop(context);

返回主视图

【讨论】：

【解决方案2】：

这很正常，因为您的数据没有存储在持久性存储中，如 SQL lite、共享首选项等。而且您不应该将任何不重要的东西保存到持久性本地存储中，因为这对于您的应用程序大小来说太贵了。还有更多的东西是状态管理和状态管理，您不需要将数据存储在持久存储中，而不是将数据存储在临时的所谓“半持久”状态中。如果您想了解更多有关管理数据的信息，而无需疯狂地进行异步活动，您可以按照以下步骤操作。

首先是使用 vanilla Navigator push 和类构造函数传递数据（取决于您的路由类型“命名或非 ClassNamed 类型的路由”）就像提到的@dshukertjr 一样

Navigator.push(context, MaterialPageRoute(
  builder: (context) => ProfilePage(user_id: userid, user_name:username, mobile_number:mobilenumber, user_address:useraddress,user_Email: userEmail,)
));

或者改用命名路由

Navigator.pushNamed(context, PackageWeight.routeName, arguments: Your data here);

在这里了解命名路线： https://flutter.dev/docs/cookbook/navigation/named-routes

优点：这很简单，
缺点：您不能仅将数据传递给整个应用程序，因为这不足以管理许多小部件的状态。

二是使用提供者/状态管理将当前数据保存在本地了解状态管理。提示：可以使用provider包，很简单，加个map类解析数据 https://flutter.dev/docs/development/data-and-backend/state-mgmt/simple

优点：这对于管理许多小部件的状态非常好。
缺点：有时使用提供者和消费者来执行简单的任务（例如保存按钮保存等）有点过头了
个人建议：学习这个，你不会后悔的，因为你几乎可以在任何地方和任何情况下使用它来管理状态和数据（半持久化）。

【讨论】：

非常感谢您提供的信息，我会阅读的