Flutter 如何从 SQLite 数据库中的数据对列表进行分组？

问题描述

我是新手，我正在使用包 grouped_list 将列表与 SQLite 数据库中的数据分组，grouped_list 可以很好地处理现有列表，就像它的示例一样，但是当我用从 SQLite 数据库中检索到的数据替换它时，它等于列表然后它不起作用，我收到错误：

The following NoSuchMethodError was thrown building GroupedListView<dynamic,String>(dirty,state: _GroupedListViewState<dynamic,String>#c2ba2):
Class 'DrinkDatabase' has no instance method '[]'.
Receiver: Instance of 'DrinkDatabase'
Tried calling: []("drinkGroup")

下面是我的代码。如果您需要更多信息，请告诉我，请帮助，谢谢！

GroupedListView<dynamic,String>(
  shrinkWrap: true,elements: homeController.drinkList,groupBy: (element) => element['drinkGroup'],groupComparator: (value1,value2) => value2.compareTo(value1),itemComparator: (item1,item2) =>
      item1['drinkDateTime'].compareTo(item2['drinkDateTime']),order: GroupedListOrder.DESC,useStickyGroupSeparators: true,groupSeparatorBuilder: (String value) =>
      Container(),itemBuilder: (c,element) {
    return Container();
  },)

这是我声明列表的方式：

List drinkList = List<DrinkDatabase>();

和类 DrinkDatabase：

class DrinkDatabase {
  int drinkId;
  int drinkVolume;
  String drinkGroup;
  String drinkCategory;
  String drinkDateTime;

  DrinkDatabase({
    this.drinkId,this.drinkVolume,this.drinkGroup,this.drinkCategory,this.drinkDateTime,});

  Map<String,dynamic> toMap() {
    return {
      "drinkId": drinkId,"drinkVolume": drinkVolume,"drinkGroup": drinkGroup,"drinkCategory": drinkCategory,"drinkDateTime": drinkDateTime,};
  }

  @override
  String toString() {
    return 'drinkTable('
        '"drinkId": ${this.drinkId},'
        '"drinkVolume": ${this.drinkVolume},'
        '"drinkGroup": ${this.drinkGroup},'
        '"drinkCategory": ${this.drinkCategory},'
        '"drinkDateTime": ${this.drinkDateTime},';
  }
}

解决方法

我做了什么，对我有用

声明列表的方式

List drinkList = [];

然后换行

elements: homeController.drinkList,

与

elements: drinkList,

从数据库查询结果列表构建列表

Future<void> getSampleList() async {
    drinkList.clear();
    List<Map<String,dynamic>> result =
        await DrinkDatabaseHelper.instance.queryAll();
    print('result= $result');
    var map = new Map<String,dynamic>();
    for (int i = 0; i < result.length; i++) {
      map['drinkId'] = result[i]['drinkId'].toString();
      map['drinkVolume'] = result[i]['drinkVolume'].toString();
      map['drinkGroup'] = result[i]['drinkGroup'];
      map['drinkCategory'] = result[i]['drinkCategory'];
      map['drinkDateTime'] = result[i]['drinkDateTime'];
      drinkList.add(Map<dynamic,String>.from(map));
    }

在 DrinkDatabaseHelper 中

Future<List<Map<String,dynamic>>> queryAll() async {
    Database db = await instance.database;
    return await db.query(_tableName);
  }

如果您有更多问题，请告诉我