appdev's questions

你好，我正在尝试将 nestedJson 检索到 dart，主要我将使用具有类似数据嵌套 Json 的 API 调用，因此下面是我尝试的示例，看看它是否有效。所以我的主要问题是我没有得到预期的输出。下面提到的是我的代码文件，如果这看起来是错误的或乏味的，请指导我正确的方法。

main.dart
void main() {

var myMap = {
"name": "dastagir",
"age": 34,
"city":"Shangai",
 
 "address": [
   { // Map 1
    "country": "china",
    "city": "Shanghai"
   },
   { // Map 2
     "country": "Bangaldesh",
     "city": "Dhaka"
   },
 ]
};
var obj = Person.fromJson(myMap);
print(obj.name);
print(obj.age);
print(obj.city);
print(obj.address);
print("=======================================");

var myAddress = obj.address;
myAddress!.map((e){
print(e.country);
 }).toList();
}

nested_json.dart
class Person{
  String? name;
  int? age;
  String? city;
  List<Address>? address;
  Person({this.name, this.age, this.city, this.address});

  Person.fromJson(Map<String, dynamic> json){
    name = json['name'];
    age = json['age'];
    city = json['city'];

    if(json['address']!=null){
      address=<Address>[];
    }
    else{
        (json['address'] as List).forEach((e){
          address!.add(Address.fromJson(e));
        });
    }
  }
}

// this is for inner Json List
class Address{
  String? country;
  String? city;
    
  Address({this.country, this.city});

  Address.fromJson(Map<String, dynamic> json){
    country = json['country'];
    city = json['city'];
  }
}`

大家好，我无法在我的 Flutter 页面中导航：

当我在 FLOATINGACTIONBUTTON onPressFunction 上运行此命令时（

onPressed: () {
                Navigator.of(context).pushNamed('/new_note');
              },

我收到以下错误， 这是我用于笔记应用程序的代码结构：Could not find a generator for route RouteSettings("/new_note", null) in the _WidgetsAppState.

main.dart:
import 'package:flutter/material.dart';
import 'package:notes_app/pages/start_page.dart';

void main() {
  runApp(const NoteMain());
}

class NoteMain extends StatelessWidget {
  const NoteMain({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(debugShowCheckedModeBanner: false, home: StartPage());
  }
}

start_page.dart
import 'package:flutter/material.dart';
import '../components/text_widget.dart';
import '../components/title_text_widget.dart';

class StartPage extends StatefulWidget {
  const StartPage({super.key});

  @override
  State<StartPage> createState() => _StartPageState();
}

class _StartPageState extends State<StartPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Color(0xff333333),
      appBar: AppBar(
        // setting default color for our Icons to white
        iconTheme: IconThemeData(color: Colors.white, size: 24),
        backgroundColor: Color(0xff333333),
        // calling TextWidget and initializing it
        title: TitleTextWidget(
          title: "NOTES",
          fontSize: 24.0,
          fontColor: Colors.white,
        ),
        actions: [
          Container(
            margin: EdgeInsets.symmetric(horizontal: 8.0),
            child: IconButton(
              //TODO: MAKE SEARCH for NOTES
              onPressed: () {},
              icon: Icon(Icons.search),
            ),
          ),
        ],
      ),

      // BODY
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Image(image: AssetImage('assets/take_note.png')),

          Divider(
            height: 10.0,
            color: Colors.white,
            indent: 100,
            endIndent: 100,
          ),

          TextWidget(
            title: 'Start Adding Notes',
            fontSize: 18.0,
            fontWeight: FontWeight.normal,
            fontColor: Colors.white,
          ),
        ],
      ),

      floatingActionButton: Builder(
        builder:
            (context) => FloatingActionButton(
              backgroundColor: Colors.white,
              // TODO: ADD FUNUCTIONALITY IN HIVEDB
              onPressed: () {
                Navigator.of(context).pushNamed('/new_note');
              },

              child: Icon(
                Icons.add_circle_sharp,
                color: Color(0xff333333),
                size: 34,
              ),
            ),
      ),
    );
  }
}

new_note.dart
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';

import '../components/title_text_widget.dart';

class NewNote extends StatefulWidget {
  const NewNote({super.key});

  @override
  State<NewNote> createState() => _NewNoteState();
}

class _NewNoteState extends State<NewNote> {
  final _titleController = TextEditingController();
  final _notesController = TextEditingController();

  @override
  void dispose() {
    _titleController.dispose();
    _notesController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Color(0xff333333),
      // Appbar with Actions
      appBar: AppBar(
        // setting default color for our Icons to white
        iconTheme: IconThemeData(color: Colors.white, size: 24),
        backgroundColor: Color(0xff333333),
        // calling TextWidget and initializing it
        title: TitleTextWidget(
          title: "NOTES",
          fontSize: 24.0,
          fontColor: Colors.white,
        ),
        actions: [
          Container(
            margin: EdgeInsets.symmetric(horizontal: 8.0),
            child: IconButton(
              //TODO: Save Note for NOTES
              onPressed: () {},
              icon: Icon(Icons.save),
            ),
          ),
        ],
      ),
      body: Column(
        children: [
          ListTile(
            title: TextField(
              controller: _titleController,
              style: GoogleFonts.pacifico(
                textStyle: TextStyle(
                  fontSize: 36.0,
                  color: Colors.white,
                  letterSpacing: 3,
                ),
              ),
              decoration: InputDecoration(
                hintText: 'Enter Title',
                hintStyle: TextStyle(color: Colors.white),
              ),
            ),
          ),
          ListTile(
            title: TextField(
              controller: _notesController,
              style: GoogleFonts.pacifico(
                textStyle: TextStyle(
                  fontSize: 18.0,
                  color: Colors.white,
                  letterSpacing: 3,
                ),
              ),
              decoration: InputDecoration(
                hintText: 'Enter Title',
                hintStyle: TextStyle(color: Colors.white),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

尝试在 FAB 中添加单独的 Builder，然后尝试路由，仍然出现同样的错误