flutter - 如何在Flutter中存储列表？

Question

我试图在Flutter中使用Hive存储和获取列表，但是出现范围错误。

    int steps = 0;
    List<int> stepCountList = List(7);
    var time = DateTime.now();

   // This is my method for a listener that updates when it detects a change,
    void _onData(int newValue) async {
    fetchSteps();
    steps = stepCountList[time.weekday] ?? 0;
    stepDivider += newValue;
    stepCountList.insert(time.weekday - 1, steps);
     moneyLottoBox.put('stepCountList', stepCountList);
  }

 void fetchSteps() {
    stepCountList = moneyLottoBox.get('stepCountList');
    if (stepCountList == null) {
      moneyLottoBox.put('stepCountList', <int>[7]);
      stepCountList = moneyLottoBox.get('stepCountList');
    }
  }
// I create my MoneyLotto box here,
var moneyLottoBox = Hive.box('moneyLottoBox');
Future<void> main async {
 moneyLottoBox = await Hive.openBox('box');
}

今天对我来说是星期六，对我来说 time.weekday的值为6，但是当我尝试 print(stepCountList[6])时，它向我显示错误

RangeError (index): Invalid value: Only valid value is 0: 6

Answer 1

您不能在固定长度List上使用insert()方法，按固定长度，我的意思是当您以这种方式声明List<int> stepCountList = List(7);时
编辑了代码，现在应该可以了

void _onData(int newValue) async {
    fetchSteps();
    steps = stepCountList[time.weekday] ?? 0;
    stepDivider += newValue;
    //stepCountList.insert(time.weekday - 1, steps);this is not correct
    stepCountList[time.weekday -1] = steps; // this should be the approach
     moneyLottoBox.put('stepCountList', stepCountList);
  }


void fetchSteps() {
    stepCountList = moneyLottoBox.get('stepCountList');
    if (stepCountList == null) {
     /* moneyLottoBox.put('stepCountList', <int>[7]); this statement is the 
reason for your error because your are storing a growable list instead of fixed list in the hive */

moneyLottoBox.put('stepCountList', List<int>(7));// try this instead 
// or u can use this moneyLottoBox.put('stepCountList', stepCountList);
      stepCountList = moneyLottoBox.get('stepCountList');
    }
  }