我在 flutter 中使用滑块尝试保存首选项中的值，但它没有在 ui 中更新

Question

这是我的课程，它包含带有音量 + 和 - 按钮的滑块 使用需要保存在首选项中的按钮点击滑块后，当我返回到此屏幕时，它需要显示首选项保存的值。

class AppSettings extends StatefulWidget {
      const AppSettings({super.key});
    
      @override
      State<AppSettings> createState() => _AppSettingsState();
    }
    
    class _AppSettingsState extends State<AppSettings> {
      double _volume = 0;
    
      double sliderValue = 0;
      double? sliderSavedValue;
      final double _minValue = 0.0;
      final double _maxValue = 100.0;
      bool isSelected = false;
      final GlobalKey _sliderKey = GlobalKey();
    
      void toggleSwitch(bool value){
        setState(() {
          isSelected=!isSelected;
        });
      }
    
      @override
      void initState() {
        super.initState();
        SharedPreferencesService().getDouble("slider_value").then((value) {
          setState(() {
            sliderValue = value;
            debugPrint("Print slider value : $sliderValue");
    
            SharedPreferencesService().setDouble("slider_value", sliderValue);
          });
        });
        FlutterVolumeController.updateShowSystemUI(false);
        FlutterVolumeController.addListener((volume) {
          setState(() {
            sliderValue = volume;
            SharedPreferencesService().setDouble("slider_value", sliderValue);
          });
        });
      }
    
      void _incrementSlider() {
        setState(() {
          if (sliderValue < _maxValue) {
            sliderValue = (sliderValue + 10).clamp(_minValue, _maxValue);
            FlutterVolumeController.setVolume(sliderValue);
            SharedPreferencesService().setDouble("slider_value", sliderValue);
          }
        });
      }
    
      void _decrementSlider() {
        setState(() {
          if (sliderValue > _minValue) {
            sliderValue = (sliderValue - 10).clamp(_minValue, _maxValue);
            FlutterVolumeController.setVolume(sliderValue);
    
            SharedPreferencesService().setDouble("slider_value", sliderValue);
          }
        });
      }
      @override
      Widget build(BuildContext context) {
        debugPrint("Print slider value inside: $sliderValue");
        debugPrint("Print slider value inside sliderSavedValue: $sliderSavedValue");
        return Scaffold(
          resizeToAvoidBottomInset: false,
          appBar: AppBar(
            elevation: 0.5,
            shadowColor: Colors.white,
            title: const Row(
              children: [
                SizedBox(width: 10.0),
                Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      "App Settings",
                      style:
                          TextStyle(fontSize: 22.0, fontWeight: FontWeight.bold),
                    )
                  ],
                )
              ],
            ),
          ),
          body: SafeArea(
            child: Padding(
              padding: const EdgeInsets.only(left: 20.0, right: 12.0, top: 12.0),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  const Padding(
                    padding: EdgeInsets.only(bottom: 8.0),
                    child: Text("Volume", style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),),
                  ),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.start,
                    children: [
                      InkWell(
                        onTap: () {
                          _decrementSlider();
                        },
                        child: Container(
                          width: 36,
                          height: 36,
                          decoration: BoxDecoration(
                              borderRadius: BorderRadius.circular(6),
                              color: Colors.white,
                            border: Border.all(color: Colors.black, width: 2)
                          ),
                          child: const Icon(Icons.remove),
                        ),
                      ),
                      Expanded(
                        child: Slider(
                          key: _sliderKey,
                          value: sliderValue,
                          min: _minValue,
                          max: _maxValue,
                          thumbColor: Colors.black,
                          activeColor: Colors.black,
                          inactiveColor: AppColors.colorDarkGrey,
    
                          onChanged: (newValue) {
                            setState(() {
                              sliderValue = newValue;
                              FlutterVolumeController.setVolume(newValue);
                              SharedPreferencesService().setDouble("slider_value", sliderValue);
                            });
                          },
                        ),
                      ),
                      InkWell(
                        onTap: _incrementSlider,
                        child: Container(
                          width: 36,
                          height: 36,
                          decoration: BoxDecoration(
                              borderRadius: BorderRadius.circular(6),
                              color: Colors.black,
                              border: Border.all(color: Colors.black, width: 2)
                          ),
                          child: const Icon(Icons.add, color: Colors.white,),
                        ),
                      ),
                    ],
                  ),
                  const Padding(
                    padding: EdgeInsets.only(top: 14.0, bottom: 18),
                    child: Text("", style: TextStyle(fontSize: 18),),
                  ),
                  Row(
                    children: [
                      const Text("", style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),),
                      const Spacer(),
                      Switch(
                        value: isSelected ,
                        onChanged: toggleSwitch,
                        activeColor: Colors.white,
                        inactiveThumbColor: Colors.black,
                        activeTrackColor: Colors.black,
                      )
                    ],
                  )
                ],
              ),
            ),
          ),
        );
      }
    }

我正在尝试保存首选项中的值并获取该值 但滑块 ui 中的值始终显示为 1.0 在初始化状态下它打印正确 如何解决这个问题？

Answer 1

你必须创建一个 SharedPreferencesService() 实例，因为每次它生成一个新实例时，你都会面临这个问题