颤振开关自行关闭

Question

我创建了一个 Flutter 入门工具包，允许我在应用内切换主题。

现在效果很好，但有一个小问题。

我已将切换按钮放在设置屏幕中， 但是当我转到另一个屏幕然后返回设置屏幕时 - 开关按钮似乎会自行进入关闭模式。

我附上一张图片和my code on github，以便你们明白我的意思。

class ThemeSwitchState extends State {
  bool switchControl = false;

  Future<bool> darkMode() async {
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    return sharedPreferences.getBool("isDark");
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<bool>(
      future: darkMode(),
      builder: (context, _snapshot) {
        return Transform.scale(
          scale: 1.5,
          child: Switch(
            value: _snapshot.data ?? false,
            onChanged: (value) {
              save(value);
              setState(() {

              });
            },
            activeColor: CustomColors().duskBlue,
            activeTrackColor: CustomColors().noroGrey,
            inactiveThumbColor: CustomColors().lureGrey,
            inactiveTrackColor: CustomColors().noroGrey,
          ),
        );
      },
    );
  }

  void save(bool value) async{
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    await sharedPreferences.setBool("isDark", value);
  }

  void toggleSwitch(bool value) {
    ThemeChanger _themeChanger =
        Provider.of<ThemeChanger>(context, listen: false);

    if (switchControl == false) {
      setState(() {
        switchControl = true;
      });
      print('Theme is Dark');

      _themeChanger.setTheme(CustomThemes.darkTheme.copyWith(
          textTheme:
              CustomThemes.darkTextTheme(CustomThemes.darkTheme.textTheme)));
    } else {
      setState(() {
        switchControl = false;
      });
      print('Theme is Light');

      _themeChanger.setTheme(CustomThemes.lightTheme.copyWith(
          textTheme:
              CustomThemes.lightTextTheme(CustomThemes.lightTheme.textTheme)));
    }
  }
}

Answer 1

您可以使用https://pub.dev/packages/shared_preferences中的SharedPreferences 保存 CheckBox

的最后一个值

我写了一个例子

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

class Settings extends StatefulWidget {
  @override
  _SettingsState createState() => _SettingsState();
}

class _SettingsState extends State<Settings> {

  Future<bool> darkMode() async{
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    return sharedPreferences.getBool("isNight");
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          children: <Widget>[
            Text("Night Mode"),
            FutureBuilder<bool>(
              future: darkMode(),
              builder: (context, _snapshot){
                return Checkbox(
                  value: _snapshot.data ?? false,
                  onChanged: (value){
                    save(value);
                    setState(() {
                       toggleSwitch(value);
                    });
                  },
                );
              },
            )
          ],
        ),
      ),
    );
  }


  void save(bool value) async{
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    await sharedPreferences.setBool("isNight", value);
  }
}

编辑：带开关

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

class Settings extends StatefulWidget {
  @override
  _SettingsState createState() => _SettingsState();
}

class _SettingsState extends State<Settings> {

  Future<bool> darkMode() async{
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    return sharedPreferences.getBool("isNight");
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          children: <Widget>[
            Text("Night Mode"),
            FutureBuilder<bool>(
              future: darkMode(),
              builder: (context, _snapshot){
                return Switch(
                  value: _snapshot.data ?? false,
                  onChanged: (value){
                    save(value);
                    setState(() {

                    });
                  },
                );
              },
            )
          ],
        ),
      ),
    );
  }


  void save(bool value) async{
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    await sharedPreferences.setBool("isNight", value);
  }
}

UPDATE 使用 value 代替 switchControl

  void toggleSwitch(bool value) {
    ThemeChanger _themeChanger =
        Provider.of<ThemeChanger>(context, listen: false);

    if (value) {
      setState(() {
        switchControl = true;
      });
      print('Theme is Dark');

      _themeChanger.setTheme(CustomThemes.darkTheme.copyWith(
          textTheme:
              CustomThemes.darkTextTheme(CustomThemes.darkTheme.textTheme)));
    } else {
      setState(() {
        switchControl = false;
      });
      print('Theme is Light');

      _themeChanger.setTheme(CustomThemes.lightTheme.copyWith(
          textTheme:
              CustomThemes.lightTextTheme(CustomThemes.lightTheme.textTheme)));
    }
  }
}