无法通过TextField onChanged方法更新状态

Question

我正在尝试使用状态存储的列表构建 TextField 的列表。我尝试使用 onChanged 方法从状态中更新特定值，但是这样做的方式无效。

以下是代码示例：

class AlarmLimitScreen extends StatefulWidget {   AlarmLimitScreen();

  @override   _AlarmLimitScreenState createState() =>
_AlarmLimitScreenState(); }

class _AlarmLimitScreenState extends State<AlarmLimitScreen> {   var alarmLimitLists = [];

  void initState() {
    super.initState();
    _getAlarmLimitFromDb();   }

  void _getAlarmLimitFromDb() async {
    final alarmLimits = await DBProvider.db.getAlarmLimits();
    // The data structure is similar to the default one below.
    if (alarmLimits.length != 0) {
      setState(() {
        alarmLimitLists = alarmLimits;
      });
    } else {
      //This is the default structure. 
      setState(() {
        alarmLimitLists = [
          {
            "id": 1,
            "name": "Field 1",
            "key": "field1",
            "min": null,
            "max": null,
          },
          {
            "id": 2,
            "name": "Field 2",
            "key": "field2",
            "min": null,
            "max": null,
          },
          {
            "id": 3,
            "name": "Field 3",
            "key": "field3",
            "min": null,
            "max": null,
          },
      });
    }   }

  void _submitAlarmLimit() async {
    // Always print the default state
    print("Saved=========: $alarmLimitLists");   }

  @override   Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Alarm Limits'),
      ),
      body: Container(
        padding: EdgeInsets.symmetric(vertical: 10.0, horizontal: 20.0),
        child: Column(
            crossAxisAlignment: CrossAxisAlignment.end,
            mainAxisAlignment: MainAxisAlignment.start,
            mainAxisSize: MainAxisSize.max,
            children: <Widget>[
              _displayAlarmLimitLists(),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 12.0),
                child: ButtonTheme(
                  minWidth: 170.0,
                  height: 50.0,
                  child: RaisedButton(
                    onPressed: _submitAlarmLimit,
                    child: Text(
                      'Save',
                      style: TextStyle(
                        fontSize: 20.0,
                        fontWeight: FontWeight.w400,
                      ),
                    ),
                    color: Color(0xFFB7282C),
                    textColor: Colors.white,
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(8.0),
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
    );   }

  Widget _displayAlarmLimitLists() {
    return ListView.builder(
      shrinkWrap: true,
      scrollDirection: Axis.vertical,
      itemCount: alarmLimitLists.length,
      itemBuilder: (context, int) {
        return Container(
          padding: EdgeInsets.symmetric(vertical: 6.0),
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            mainAxisSize: MainAxisSize.max,
            children: <Widget>[
              Text(
                alarmLimitLists[int]['name'],
                style: TextStyle(
                  fontSize: 18.0,
                ),
              ),
              Row(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                mainAxisSize: MainAxisSize.max,
                children: <Widget>[
                  Padding(
                    padding: const EdgeInsets.only(right: 4.0),
                    child: SizedBox(
                      width: 80,
                      height: 45,
                      child: TextField(
                        onChanged: (min) {
                        //===================================
                        //I'm changing the value here.
                        //===================================
                          alarmLimitLists[int]['min'] = min.toString();
                          setState(() {
                            alarmLimitLists = alarmLimitLists;
                          });
                        },
                        keyboardType: TextInputType.number,
                        decoration: InputDecoration(
                          border: OutlineInputBorder(),
                          labelText: 'Min',
                        ),
                      ),
                    ),
                  ),
                  Padding(
                    padding: const EdgeInsets.only(left: 4.0),
                    child: SizedBox(
                      width: 80,
                      height: 45,
                      child: TextField(
                        onChanged: (max) {
                          setState(() {
                            alarmLimitLists[int]['max'] = max;
                          });
                        },
                        keyboardType: TextInputType.number,
                        decoration: InputDecoration(
                          border: OutlineInputBorder(),
                          labelText: 'Max',
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ],
          ),
        );
      },
    );   } }

状态没有更新。

但是，如果我将 alarmLimitLists 存储为变量并在 onChanged 上对其进行修改，则它可以正常工作。