如何将颤动页面（小部件）重置为初始状态（应用程序首次构建时的状态）

Question

假设我的页面上有一些滑块和开关，我更改了它们的状态并修改了它们，我知道我们这样做是setState为了显示小部件树的更改状态并重建它，但我想知道是否有办法撤消所有这些更改并返回到初始状态（应用程序最初构建时的状态）？

Answer 1

如果你想开箱即用

void main() => runApp(MaterialApp(home: DummyWidget()));

class DummyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) => HomePage();
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  bool _enabled = false; // For Switch
  double _value = 0; // For Slider

  // This is the trick!
  void _reset() {
    Navigator.pushReplacement(
      context,
      PageRouteBuilder(
        transitionDuration: Duration.zero,
        pageBuilder: (_, __, ___) => DummyWidget(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Switch(
            value: _enabled,
            onChanged: (newValue) => setState(() => _enabled = newValue),
          ),
          Slider(
            value: _value,
            onChanged: (newValue) => setState(() => _value = newValue),
          ),
          FlatButton(
            onPressed: _reset,
            child: Text('RESET'),
          ),
        ],
      ),
    );
  }
}

更好的方法可能是使用密钥。这是关键方法

Answer 2

一个简单的技巧是使用相同的路线弹出和推送。像这样：

Navigator.popAndPushNamed(context, "same_route");

Answer 3

截屏：

用于key改变状态。

import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(home: HomePage()));

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int _count = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: KeyedSubtree(
        key: ValueKey<int>(_count),
        child: Column(
          children: [
            MainPage(),
            ElevatedButton(
              onPressed: () => setState(() => ++_count),
              child: Text('RESET'),
            )
          ],
        ),
      ),
    );
  }
}

class MainPage extends StatefulWidget {
  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  bool _enabled = false; // For Switch
  double _value = 0; // For Slider.

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Switch(
          value: _enabled,
          onChanged: (newValue) => setState(() => _enabled = newValue),
        ),
        Slider(
          value: _value,
          onChanged: (newValue) => setState(() => _value = newValue),
        ),
      ],
    );
  }
}