如何在 Hive (Flutter) 中存储列表？答案

【问题标题】：How to store a List in Hive (Flutter)?如何在 Hive (Flutter) 中存储列表？
【发布时间】：2020-10-17 21:34:57
【问题描述】：

我尝试在 Flutter 中使用 Hive 存储和获取列表，但出现范围错误。

    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，time.weekday 的值对我来说是 6，但是当我尝试 print(stepCountList[6]) 时它显示错误

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

【问题讨论】：

如何打印List？只是问，考虑到 0 到 6，List length 不应该是 7 吗？
当我打印 stepCountList[6] 时它会打印这个错误
好的，print 它的长度优先。 print(stepCountList.length).
将长度打印为 1
stepCountList = moneyLottoBox.get('stepCountList', defaultValue: <int>[6]); 这是覆盖最初的List

标签： flutter dart flutter-hive

【解决方案1】：

您不能在固定长度列表上使用insert() 方法，固定长度是指当您以这种方式声明时List<int> stepCountList = List(7); 编辑了代码，现在应该可以工作了

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');
    }
  }

【讨论】：