flutter - 颤振 | 图表馅饼 | 来自数据库的信息

Question

我想从数据库创建一个数据图表。但是当我运行它时返回错误null。在此处输入图像描述

List<charts.Series<Transactions, String>> _series(BuildContext context) {

    final myTransaction = Provider.of<Transaction>(context).myTransaction;

    List<Transactions> data = List<Transactions>();
    data.add(Transactions(category: myTransaction.category, amount: myTransaction.amount, color: myTransaction.color));

    return [
      charts.Series<Transactions, String>(
          id: 'Transactions',
          domainFn: (Transactions transactions, _) => transactions.category,
          measureFn: (Transactions transactions, _) => transactions.amount,
          labelAccessorFn: (Transactions transactions, _) => '\$${transactions.amount}',
          colorFn: (Transactions transactions, _) =>
              charts.ColorUtil.fromDartColor(
                  HexColor.fromHex(transactions.color)),
          data: data
      )
    ];
  }

标签： flutterflutter-provider

Answer 1

您需要myTransaction在Transaction课堂上进行初始化。

 Transactions myTransaction = Transaction() ;