Question

我在抽屉中有一个ListView，希望它只能被构建一次。我知道它正在被处置，因为每次我关闭并重新打开抽屉时滚动位置都会重置，例如，打开抽屉，滚动到列表底部，关闭抽屉，重新打开它，您会明白我的意思。如何使它记住状态？

这是一个最小的工作示例：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final europeanCountries = [
    'Albania',
    'Andorra',
    'Armenia',
    'Austria',
    'Azerbaijan',
    'Belarus',
    'Belgium',
    'Bosnia and Herzegovina',
    'Bulgaria',
    'Croatia',
    'Cyprus',
    'Czech Republic',
    'Denmark',
    'Estonia',
    'Finland',
    'France',
    'Georgia',
    'Germany',
    'Greece',
    'Hungary',
    'Iceland',
    'Ireland',
    'Italy',
    'Kazakhstan',
    'Kosovo',
    'Latvia',
    'Liechtenstein',
    'Lithuania',
    'Luxembourg',
    'Macedonia',
    'Malta',
    'Moldova',
    'Monaco',
    'Montenegro',
    'Netherlands',
    'Norway',
    'Poland',
    'Portugal',
    'Romania',
    'Russia',
    'San Marino',
    'Serbia',
    'Slovakia',
    'Slovenia',
    'Spain',
    'Sweden',
    'Switzerland',
    'Turkey',
    'Ukraine',
    'United Kingdom',
    'Vatican City'
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawer: ListView.builder(
        itemCount: europeanCountries.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(europeanCountries[index]),
          );
        },
      ),
    );
  }
}

Answer 1

您需要做的就是像这样使用PageStorageKey：

ListView.builder(
  key: PageStorageKey("my_key"),
  // ...
)

如何防止抽屉丢弃？

1 个答案: