Flutter报错_TypeError：int无法转换为double类型的问题排查

DevOps 小满

2026-7-13

问题定位与解决方案

错误根源

报错_TypeError (type 'int' is not a subtype of type 'double' in type cast)的核心原因是List.castFrom(data['c'])的使用方式错误。Finnhub API返回的c（收盘价）数组中可能同时包含整数和浮点数，而List.castFrom不会真正转换元素类型，仅做类型断言。当数组存在int类型值时，直接断言为List<double>会导致后续访问元素时触发类型不匹配。

修复代码

将列表元素逐个转换为目标类型，替代直接的类型断言：

Future<void> _fetchChartData() async {
    final response = await http.get(Uri.parse(
        'https://finnhub.io/api/v1/stock/candle?symbol=${widget.symbol}&resolution=${widget.resolution}&from=${widget.fewDaysAgoTimestamp}&to=${widget.currentTimestamp}&token=$apiKey'));

    if (response.statusCode == 200) {
      final data = json.decode(response.body);
      final List<_ChartData> newChartData = [];

      // 安全转换收盘价为double类型
      final List<double> values = (data['c'] as List)
          .map((e) => double.parse(e.toString()))
          .toList();
      // 安全转换时间戳为int类型
      final List<int> timestamps = (data['t'] as List)
          .map((e) => e as int)
          .toList();

      for (int i = 0; i < values.length; i++) {
        final DateTime date =
            DateTime.fromMillisecondsSinceEpoch(timestamps[i] * 1000);
        var randomValue = values[i];
        newChartData.add(
          _ChartData(date, randomValue),
        );

        if (i == 0) {
          _maxValue = _minValue = randomValue.toInt();
        } else {
          _maxValue = max(_maxValue, randomValue.toInt());
          _minValue = min(_minValue, randomValue.toInt());
        }
      }

      setState(() {
        _chartData = newChartData;
        _isGoingUp = _chartData.first.y <= _chartData.last.y;
      });
    }
  }