如何在Flutter中添加/求和TextFormField值？

Question

如何在Flutter中添加几个表单字段的值以动态计算总字段？想象一下如果三个文本字段的值分别为1、2、3，则总字段应显示为6。

我可以使用double.parse(value)将值转换为两倍。

代码：

class _GivingPageState extends State<GivingPage> {
  final _formKey = GlobalKey<FormState>();

  double collection1;
  double collection2;
  double collection3;
  double total;

  @override
  void initState() {
    collection1 = 0;
    collection2 = 0;
    collection3 = 0;
    total = 0;

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: GestureDetector(
          onTap: () {
            FocusScope.of(context).unfocus();
          },
          child: Column(
            children: <Widget>[
              Expanded(
                child: buildContent(),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget buildContent() {
    return Container(
        color: Colors.white,
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          child: lightCard(
              child: Container(
            padding: EdgeInsets.only(left: 0.0, right: 10, top: 10, bottom: 10),
            child: Padding(
              padding: const EdgeInsets.only(left: 18.0, bottom: 10),
              child: Container(
                child: Form(
                  key: _formKey,
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: <Widget>[
                      Padding(
                        padding: const EdgeInsets.only(left: 0.0, bottom: 10),
                        child: Text(
                          'Collection Baskets',
                          style: TextStyle(
                              fontSize: 16, fontWeight: FontWeight.bold),
                        ),
                      ),
                      Text('Which collection baskets(s) are you giving to?'),
                      SizedBox(height: 15),
                      _buildBasket(
                        collectionName: 'Amount 1',
                        collection: collection1,
                      ),
                      SizedBox(height: 10),
                      _buildBasket(
                        collectionName: 'Amount 2',
                        collection: collection2,
                      ),
                      SizedBox(height: 10),
                      _buildBasket(
                        collectionName: 'Amount 3',
                        collection: collection3,
                      ),
                      SizedBox(height: 10),
                      _buildTotal()
                    ],
                  ),
                ),
              ),
            ),
          )),
        ));
  }

  void _updateTotal() {
    setState(() {
      total = collection1 + collection2 + collection3;
    });
  }

  Row _buildBasket(
      {@required String collectionName, @required double collection}) {
    return Row(
      children: <Widget>[
        Expanded(
          flex: 1,
          child: Text(
            collectionName,
            style: TextStyle(fontSize: 16),
          ),
        ),
        SizedBox(width: 10),
        Expanded(
          flex: 1,
          child: Row(
            children: <Widget>[
              Text(
                '£',
                style: TextStyle(fontSize: 20),
              ),
              SizedBox(width: 10),
              Expanded(
                child: numberFormField(
                    onChanged: (value) {
                      setState(() {
                        collection = double.parse(value);
                        _updateTotal();
                      });
                    },
                    textFieldKey: null),
              ),
            ],
          ),
        ),
      ],
    );
  }

  Row _buildTotal() {
    return Row(
      children: <Widget>[
        Expanded(
          flex: 1,
          child: Text(
            'Total',
            style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
          ),
        ),
        SizedBox(width: 10),
        Expanded(
          flex: 1,
          child: Row(
            children: <Widget>[
              Text(
                '£',
                style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
              ),
              SizedBox(width: 10),
              Expanded(
                child: Container(
                  height: 50,
                  decoration: BoxDecoration(
                    color: AppColors.secondaryElement,
                    borderRadius: Radii.k25pxRadius,
                  ),
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Text(
                        "${formatNumber(amount: total)}",
                        textAlign: TextAlign.center,
                        style: TextStyle(
                            fontWeight: FontWeight.bold, fontSize: 20),
                      ),
                    ],
                  ),
                ),
              ),
            ],
          ),
        ),
      ],
    );
  }
}

Answer 1

这对您有用吗？

recipe