Question

我有一个带有ListView的小部件，我经常使用Navigator.push()进行导航。我正在尝试使用键（PageStorageKey / UniqueKey / GlobalKey）来保持滚动，而没有任何运气。

https://gist.github.com/JellyO1/dd8b50a5bcf2e5c10d7a4047427943c8

Answer 1

我相信您在弹出堆栈顶部的屏幕时正在尝试保存滚动状态。您可以通过几种方式实现此目的，但是可以通过提供初始偏移量并使用自定义ScrollController将其保存回上下文弹出窗口中来完成。这是您编辑的示例。

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      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> {
  double scrollOffset = 0.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(),
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          scrollOffset = await Navigator.of(context).push(MaterialPageRoute(
              builder: (context) => Scrollable(
                    scrollOffset: scrollOffset,
                  )));
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

class Scrollable extends StatefulWidget {
  final double scrollOffset;
  @override
  State createState() {
    return _ScrollableState();
  }

  Scrollable({this.scrollOffset, Key key}) : super(key: key);
}

class _ScrollableState extends State<Scrollable> {
  ScrollController myScrollController;
  List<Widget> list = List.generate(500, (index) => Text('$index'));

  @override
  void initState() {
    super.initState();
    myScrollController = ScrollController(initialScrollOffset: widget.scrollOffset);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        leading: IconButton(
          icon: Icon(Icons.arrow_back),
          onPressed: () => Navigator.of(context).pop(myScrollController.offset),
        ),
      ),
      body: ListView(
        controller: myScrollController,
        children: list,
      ),
    );
  }
}

但是，我也想知道是否有可能通过使用PageStorageKey使它变得更加简单。

注意：如果需要，请不要忘记使用WillPopScope小部件覆盖Android设备中的后退按钮。

在使用Navigator来回导航时保持状态？

1 个答案: