flutter - 在 Flutter 中解析复杂的 JSON

Question

我作为 HTTP 响应获得的 map 列表

    final List<dynamic> scoresByDay = httpResponse[0]['days']['averageScores'];    
    print(scoresByDay);

看起来像:

   [
     {"date":"27\/08\/2019","score":"30.00"},
     {"date":"28\/08\/2019","score":"67.67"},
     {"date":"29\/08\/2019","score":"73.00"},
     {"date":"30\/08\/2019","score":"59.80"},
     {"date":"31\/08\/2019","score":"57.18"},
     {"date":"01\/09\/2019","score":"50.75"},
     {"date":"02\/09\/2019","score":"50.78"},
     {"date":"03\/09\/2019","score":"50.85"},
     {"date":"04\/09\/2019","score":"48.18"},
     {"date":"05\/09\/2019","score":"58.12"}
    ]

我想从这个 json 数组中获得的是一个列表，我可以将其用于 Flutter 图表库(简单条形图)。为了使用这个简单的条形图，这个数组应该是这样的:

     final data = [
          new OrdinalSales('27', 30),
          new OrdinalSales('28', 68),
          new OrdinalSales('29', 74),
          new OrdinalSales('30', 60),
          new OrdinalSales('31', 57),
          new OrdinalSales('01', 51),
          new OrdinalSales('02', 51),
          new OrdinalSales('03', 51),
          new OrdinalSales('04', 48),
          new OrdinalSales('05', 58),

];

有没有什么方法可以使用现有的 map 列表来创建我需要显示简单条形图的 json 数组？

编辑:

我设法使用简单条形图 (https://google.github.io/charts/flutter/example/bar_charts/simple) 所需的数据创建了一个数组 (simpleBarArrayData)。但是，当我尝试插入该数组而不是在简单条形图中作为示例设置的数组时，会发生错误:

    type 'List<dynamic>' is not a subtype of type List<OrdinalSales>' 

示例数据数组:

    final data = [
      new OrdinalSales('27', 30),
      new OrdinalSales('28', 68),
      new OrdinalSales('29', 74),
      new OrdinalSales('30', 60),
      new OrdinalSales('31', 57),
      new OrdinalSales('01', 51),
      new OrdinalSales('02', 51),
      new OrdinalSales('03', 51),
      new OrdinalSales('04', 48),
      new OrdinalSales('05', 58),
    ];

创建的数组 (simpleBarArrayData) 如下所示:

   print(simpleBarArrayData);

    [
     new OrdinalSales('27',30), 
     new OrdinalSales('28',68), 
     new OrdinalSales('29',73), 
     new OrdinalSales('30',60), 
     new OrdinalSales('31',57), 
     new OrdinalSales('01',51), 
     new OrdinalSales('02',51), 
     new OrdinalSales('03',51), 
     new OrdinalSales('04',48), 
     new OrdinalSales('05',58)
    ]

我尝试用以下代码替换现有数据:

    final data = simpleBarArrayData;

然后出现错误。

Answer 1

假设你的

List json = [YOUR_GIVEN_JSON_IN_LIST];

你可以创建这个方法，这里 dates 将只有你的 dates 而 scores 有分数。

List<String> dates = [];
List<int> scores = [];

void _fetch() {
  for (var item in json) {
    String date = item["date"];
    dates.add(date.split("\/")[0]);

    String score = item["score"];
    int element = int.parse(score.split("\.")[0]);
    scores.add(element);
  }
}

void _merge() {
  // you can merge by iterating it over
  List<OrdinalSales> data = [];
  for (int i = 0; i < dates.length; i++) {
    data.add(OrdinalSales(dates[i], scores[i]));
  }
}