Android 颤振-将状态设置为另一个类

我刚开始用flifter编程。我想创建一个应用程序来跟踪食物的过期日期。 我的应用程序由以下部分组成：

• 返回MaterialApp类的main.dart，该类的内部
• 包含AppBar的home.dart、包含ListBuilder（）作为主体的Scaffold和应添加新项的FAB
• list_builder.dart，其中包含有状态小部件ListBuilder，它从items_list.dart获取字符串列表，并创建一个带有一些平铺的ListView
• items_list.dart，包含字符串列表，用于删除、添加和检索列表的函数

到目前为止，我所做的是一个带有拖尾垃圾箱图标按钮的项目列表，该按钮可以从列表中删除单个项目。一切正常。 现在我希望按下FAB键，它会触发ItemsList.addItem（），将一个项目添加到列表中。当然，这是可行的，但是屏幕上的列表（由list_builder.dart创建）不会更新，除非我删除一项

我尝试使用回调函数失败，我肯定我遗漏了一些东西

代码如下：

main.dart

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

本垒打。飞镖

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

列表\u builder.dart

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

导入“包装：颤振/材料.省道”；
导入“项目列表.省道”；
类ListBuilder扩展了StatefulWidget{
常量ListBuilder（{Key}）：超级（Key:Key）；
@凌驾
_ListBuilderState createState（）=>\u ListBuilderState（）；
}
类_ListBuilderState扩展状态{
@凌驾
小部件构建（构建上下文）{
返回ListView.builder(
itemCount:ItemsList.getItems（）.length，
itemBuilder：（上下文，索引）{
返回_buildRow（ItemsList.getItems（）[index]，index）；
},
);
}
小部件构建行（字符串项，int索引）{
返回列表块(
标题：正文(
项目,，
),
尾随：图标按钮(
图标：图标（Icons.delete），
已按下：（）{
设置状态（）{
ItemsList.removeItem（索引）；
});
},
),
);
}
}

项目列表。省道

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

类项目列表{
静态列表_项=[
“巴南”，
“拿铁”，
“卡夫”，
“葡萄酒”，
"寿司",，
“比拉”，
];
//添加项目
静态void addItem（字符串名称）=>ItemsList.\u items.add（名称）；
//删除项目
静态void removietem（inti）=>ItemsList.\u items.removeAt（i）；
//返回项目列表
静态列表getItems（）{
返回项目列表。\u项目；
}
}

我看到您在项目删除中使用了

setState

，添加项目时也应该使用它：

...
floatingActionButton: FloatingActionButton(
  onPressed: () {
    setState(() {
      ItemsList.addItem('ciao');
    });
    
    print('item added!!!');
  },
  child: const Icon(Icons.add),
),
...

---

当然，在此之前将

Home

小部件设置为

StatefulWidget

。

虽然这不是您所寻找的最佳解决方案，但是，这比将

Home

类更改为有状态小部件并重建整个小部件树要好。我修改了您的代码，使其完全按照您希望的方式工作，而无需调用

setState

函数

本垒打。飞镖

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

项目列表。省道

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

类项目列表{
最终清单=[
“巴南”，
“拿铁”，
“卡夫”，
“葡萄酒”，
"寿司",，
“比拉”，
];
StreamController\u项目=
StreamController.broadcast（）；
Stream get items=>\u items.Stream；
//添加项目
void addItem（字符串名称）{
//_重新启动流（）；
_列表。添加（名称）；
_items.sink.add（_列表）；
//_items.close（）；
}
//删除项目
无效删除项（int i）{
//_重新启动流（）；
_list.removeWhere（（element）=>element==\u list[i]）；
_items.sink.add（_列表）；
}
无效关闭（）{
_items.close（）；
}
静态最终项目列表_singleton=ItemsList._internal（）；
静态ItemsList get itemList=>ItemsList（）；
工厂项目列表（）{
返回单件；
}
ItemsList._internal（）；
}

列表\u builder.dart

import 'package:flutter/material.dart';

import 'home.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Quando Scade?',
      home: Home(),
      theme: ThemeData(
        primarySwatch: Colors.lightGreen,
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:quando_scade/items_list.dart';

import 'list_builder.dart';

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

import 'package:flutter/material.dart';

import 'items_list.dart';

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: ItemsList.getItems().length,
      itemBuilder: (context, index) {
        return _buildRow(ItemsList.getItems()[index], index);
      },
    );
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.removeItem(index);
          });
        },
      ),
    );
  }
}

class ItemsList {
  static List<String> _items = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  // to add items
  static void addItem(String name) => ItemsList._items.add(name);

  // to remove item
  static void removeItem(int i) => ItemsList._items.removeAt(i);

  // returns the list of items
  static List<String> getItems() {
    return ItemsList._items;
  }
}

class Home extends StatelessWidget {
  const Home({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Quando Scade?'),
        backgroundColor: Theme.of(context).colorScheme.primary,
      ),
      body: ListBuilder(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ItemsList.itemList.addItem('ciao');
          print('item added!!!');
        },
        child: const Icon(Icons.add),
      ),
    );
  }
}

class ItemsList {
  final _list = [
    'banane',
    'latte',
    'caffè',
    'vino',
    'sushi',
    'birra',
  ];

  StreamController<List<String>> _items =
      StreamController<List<String>>.broadcast();

  Stream<List<String>> get items => _items.stream;

  // to add items
  void addItem(String name) {
    //_reOpenStream();
    _list.add(name);
    _items.sink.add(_list);
    // _items.close();
  }

  // to remove item
  void removeItem(int i) {
    //_reOpenStream();
    _list.removeWhere((element) => element == _list[i]);
    _items.sink.add(_list);
  }

  void close() {
    _items.close();
  }

  static final ItemsList _singleton = ItemsList._internal();

  static ItemsList get itemList => ItemsList();

  factory ItemsList() {
    return _singleton;
  }

  ItemsList._internal();
}

class ListBuilder extends StatefulWidget {
  const ListBuilder({Key key}) : super(key: key);

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

class _ListBuilderState extends State<ListBuilder> {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<List<String>>(builder: (_, snapshot) {
      int itemCount = snapshot.data.length;
      return ListView.builder(
        itemCount: itemCount,
        itemBuilder: (context, index) {
          //Handle the empty list by replacing the container widget with your logic
          return itemCount <=0 ? Container(): _buildRow(snapshot.data[index], index);
        },
      );
    }, initialData: [],);
  }

  Widget _buildRow(String item, int index) {
    return ListTile(
      title: Text(
        item,
      ),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        onPressed: () {
          setState(() {
            ItemsList.itemList.removeItem(index);
          });
        },
      ),
    );
  }
}

类ListBuilder扩展StatefulWidget{
常量ListBuilder（{Key}）：超级（Key:Key）；
@凌驾
_ListBuilderState createState（）=>\u ListBuilderState（）；
}
类_ListBuilderState扩展状态{
@凌驾
小部件构建（构建上下文）{
返回StreamBuilder（生成器：（\ux，快照）{
int itemCount=snapshot.data.length；
返回ListView.builder(
itemCount:itemCount，
itemBuilder：（上下文，索引）{
//通过用逻辑替换容器小部件来处理空列表
return itemCount虽然这可能有效，但总是重建整个小部件树来更新列表并不是一个好主意。好吧，如果const构造函数将用于
ListBuilder
小部件，这不会是一个很大的问题。一般来说，同意，状态管理用于OP试图做的事情，我不是说这是一个好主意解决方法，但对于这种特定情况，
setState
将起作用。“\u list.removeWhere（（element）=>element==\u list[i]）”…您害怕“removeAt”吗？Lol…不，我不怕使用
removeAt
函数。我试图提供一种解决方案，不需要OP更改他的大部分代码。@OGx09好吧，因为这是一个只有几行代码的新项目，我很高兴听到您关于如何改进代码的任何建议。