错误：flutter/lib/ui/ui_dart_state.cc(177)] 未处理的异常：类型“double”不是类型转换中“String”类型的子类型

Question

我收到此错误，但无法弄清楚原因和位置。 我对 Flutter 有点陌生，我正在使用 hive db 和 provider 创建一个资金管理应用程序。这是我的添加交易页面， 未处理的异常：类型“double”不是类型转换中“String”类型的子类型

class _AddTransactionState extends State<AddTransaction> with TickerProviderStateMixin{
  String transTitle;
  double transAmount=0;
  DateTime transDate = DateTime.now();
  Future<void> _selectDate(BuildContext context) async {
    final DateTime pickedDate = await showDatePicker(
        context: context,
        initialDate: transDate,
        firstDate: DateTime(2010),
        lastDate: DateTime(2050));
    if (pickedDate != null && pickedDate != transDate)
      setState(() {
        transDate = pickedDate;
      });
  }
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.black,
      child: Container(
        padding: EdgeInsets.symmetric(vertical: 20, horizontal: 40),
        height: 550,
        decoration: BoxDecoration(
          color: Color(0xffE8816D),
          borderRadius: BorderRadius.only(topRight: Radius.circular(20), topLeft: Radius.circular(20)),
        ),
        child: Column(
          children: <Widget>[
            Text("New TransactionDetails", style: kdropDownTextStyle.copyWith(decoration: TextDecoration.underline),),
            SizedBox(height: 50,),
            TextField(
              onChanged: (value){transTitle = "$value";
              print(transTitle);},
              decoration: kTextFieldDecoration.copyWith(
                  hintText: 'Enter new Transaction',
                  hintStyle: TextStyle(color: Colors.black54),
              ),
            ),
            SizedBox(height: 30),
            TextField(
              onChanged: (value){
                transAmount = double.parse("$value");
                print(transAmount);
              },
              keyboardType: TextInputType.number,
              decoration: kTextFieldDecoration.copyWith(
                hintText: 'Enter Amount',
                hintStyle: TextStyle(color: Colors.black54),
              ),
            ),

            SizedBox(height: 30),
            Text("${transDate.day}-${transDate.month}-${transDate.year}",
              style: GoogleFonts.kaushanScript(textStyle: TextStyle(fontSize: 30)),
            ),
            RaisedButton(
              onPressed: () => _selectDate(context),
              child: Text('Select date'),
            ),
            FlatButton(
                onPressed: (){
                  Provider.of<TransData>(context, listen: false).addToList(
                    Item(
                      transactionType: widget.transactionType,
                      categoryName: widget.categoryName,
                      amount: transAmount,
                      dateTime: transDate,
                      transName: transTitle,
                    ));
                  Navigator.pop(context);
                },
                child: Text("Add Transaction"),
            )
          ],
        ),
      ),
    );
  }
}

这是我的交易.g.dart 文件

class ItemAdapter extends TypeAdapter<Item> {
  @override
  final typeId = 1;
  @override
  Item read(BinaryReader reader) {
    var numOfFields = reader.readByte();
    var fields = <int, dynamic>{
      for (var i = 0; i < numOfFields; i++) reader.readByte(): reader.read(),
    };
    return Item(
      transactionType: fields[0] as String,
      categoryName: fields[1] as String,
      transName: fields[2] as String,
      amount: fields[3] as double,
      dateTime: fields[4] as DateTime,
    );
  }

  @override
  void write(BinaryWriter writer, Item obj) {
    writer
      ..writeByte(5)
      ..writeByte(0)
      ..write(obj.transactionType)
      ..writeByte(1)
      ..write(obj.categoryName)
      ..writeByte(2)
      ..write(obj.transName)
      ..writeByte(3)
      ..write(obj.amount)
      ..writeByte(4)
      ..write(obj.dateTime);
  }
}