flutter - 制作新小部件后清除类(class)列表

Question

我试图学习 flutter ，但偶然发现了一个我无法解决的问题。我有一个MyApp / MyAppState类，该类具有在listVeiw.builder中使用的小部件(ovelser)列表。

import './barbutton.dart';

import './ovelser.dart';

void main() {
  runApp(MaterialApp(home: MyApp()));
}

class MyApp extends StatefulWidget {
  // This widget is the root of your application.

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  List<Widget> ovelser = [];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("progresjon"),
        backgroundColor: Colors.blue,
        actions: <Widget>[AddButton(nameOvelse)],
      ),
      body: ListView.builder(
        itemCount: ovelser.length,
        itemBuilder: (context, index) {
          final Widget ovelse = ovelser[index]; // lagrer bare ovelse objektet
          return Dismissible(
            // dismissible gjør det mulig å slette ting i listView
            key: UniqueKey(),
            onDismissed: (direction) {
              //hva som skjer når man skal slette
              setState(() {
                ovelser.removeAt(index);
              });
            },
            background: Container(
              color: Colors.red,
            ),
            //child er hva som skal være objektet som kan slettes
            child: ovelse,
          );
        },
      ),
    );
  }

  void addOvelse(String name) {
    setState(() {
      ovelser.add(Ovelser(name));
    });
    print(ovelser.length);
  }

  nameOvelse(BuildContext context) {
    TextEditingController custumcontroller = TextEditingController();
    return showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text("new activity"),
          content: TextField(
            controller: custumcontroller,
          ),
          actions: <Widget>[
            FlatButton(
              child: Text("create"),
              onPressed: () {
                String activityName = "  " + custumcontroller.text;
                addOvelse(activityName);
                Navigator.of(context).pop();
              },
            )
          ],
        );
      },
    );
  }
}

列表ovelser接受Ovelser对象。这些对象具有一个类，该类具有一个可以输入整数的列表(progresjonsList)，我可以通过AlertDialog添加该列表。
int中带有progresjonList的类的代码:

import './ovleseraddbutton.dart';

class Ovelser extends StatefulWidget {
  final String name;

  Ovelser(this.name);

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

class OvelserState extends State<Ovelser> {
  List<int> progresjonList = [];

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 80,
      width: double.infinity,
      alignment: Alignment.centerLeft,
      decoration: BoxDecoration(
          border: Border(
        top: BorderSide(width: 0.5, color: Colors.grey),
        bottom: BorderSide(width: 0.5, color: Colors.grey),
      )),
      child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: <Widget>[
            Flexible(
                child: Container(
              child: Text(widget.name,
                  overflow: TextOverflow.fade,
                  softWrap: false,
                  maxLines: 1,
                  style: TextStyle(
                      fontStyle: FontStyle.italic,
                      fontSize: 20,
                      fontWeight: FontWeight.bold)),
            )),
            OvelserAddbutton(addvalue)
          ]),
    );
  }

  void insertValue(int value) {
    setState(() {
      this.progresjonList.add(value);
    });
  }

  addvalue(BuildContext context) {
    TextEditingController custumcontroller = TextEditingController();
    return showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text("add new value"),
          content: TextField(
            controller: custumcontroller,
            keyboardType: TextInputType.number,
          ),
          actions: <Widget>[
            FlatButton(
              child: Text("add"),
              onPressed: () {
                String stringnumber = custumcontroller.text;
                int number = int.parse(stringnumber);
                insertValue(number);
                print(number);
                print(progresjonList.length);
                print(this.progresjonList);
                Navigator.of(context).pop();
              },
            )
          ],
        );
      },
    );
  }
}

问题是每次我在ovelser(在ListView中使用的列表)中创建新的小部件时，带有整数(progresjonList)的列表都会清除，因此它们为空，并且不保留以前由AlertDialog添加的值。我不明白如何避免这种情况的发生，因此我不增加整数。谁能帮我？先感谢您:)

还有两个其他的小文件，其中只包含图标小部件，我认为这不是问题所在，但如果您在这里需要它们，它们是:)

class AddButton extends StatelessWidget {
  final Function setInFunction;

  AddButton(this.setInFunction);

  @override
  Widget build(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.add),
      onPressed: () => setInFunction(context),
    );
  }
}

import 'package:flutter/material.dart';

class OvelserAddbutton extends StatelessWidget {
  final Function setInFunction;

  OvelserAddbutton(this.setInFunction);

  @override
  Widget build(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.add),
      onPressed: () => setInFunction(context),
    );
  }
}
```

Answer 1

progessjonList对于Ovelser类是本地的。您需要将overserList传递给Ovelser类。

class Ovelser extends StatefulWidget {
  final String name;
  final List<int> list;

  Ovelser(this.name, this.list);

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

然后，当您想添加到OvelserState中的列表时，只需使用

widget.list.add(/*add int here*/);

我看到的是在您的insertValue函数中

void insertValue(int value) {
  setState(() {
    widget.list.add(value);
  });
}

您传入的列表将引用原始类中的ovelser列表。