Question

当我尝试使用“文本”窗口小部件呈现item时，我收到一条错误消息，说class AddCashForm extends StatefulWidget { @override _AddCashFormState createState() => _AddCashFormState(); } class _AddCashFormState extends State<AddCashForm> { DateTime selectedDate = DateTime.now(); List<String> chipList = [ "one", "two", "three", "four", ]; void dispose() { oneController.dispose(); twoController.dispose(); super.dispose(); } @override Widget build(BuildContext context) { return Scaffold( body: Column( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Row( children: <Widget>[ ChoiceChipWidget(chipList, (item) { print('Item selected: $item'); return (item); }), ], ), RaisedButton( child: Text("Submit"), onPressed: () { }, ), // Text(item), data should appear here ], ), ); } }未定义。

如何在按下按钮时检索值并将其放在小部件中？

PYTHON_CONFIGURE_OPTS="--enable-framework" pyenv install 3.7.4

Answer 1

如果您希望该项目自动更新，而无需单击提交，请使用以下方法：

class _AddCashFormState extends State<AddCashForm> {
  final selectedDate = DateTime.now();
  final chipList = <String>[
    'one',
    'two',
    'three',
    'four',
  ];

  String item;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Row(
            children: chipList
                .map<Widget>((s) => ChoiceChip(
                      label: Text(s),
                      selected: s == item,
                      onSelected: (bool selected) {
                        setState(() {
                          item = selected ? s : null;
                        });
                      },
                    ))
                .toList(),
          ),
          Text(item ?? ''),
        ],
      ),
    );
  }
}

Answer 2

您可以创建一个字段 selectedItem ，该字段在选择项目时会更新。用 onPressed 方法更新状态。像这样：

class AddCashForm extends StatefulWidget {
  @override
  _AddCashFormState createState() => _AddCashFormState();
}

class _AddCashFormState extends State<AddCashForm> {
  DateTime selectedDate = DateTime.now();
  String selectedItem;
  List<String> chipList = [
    "one",
    "two",
    "three",
    "four",
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Row(
            children: <Widget>[
              ChoiceChipWidget(chipList, (item) {
                print('Item selected: $item');
                selectedItem = item;
                return (item);
              })
            ],
          ),
          RaisedButton(
            child: Text("Submit"),
            onPressed: () {
              setState(() {});
            },
          ),
          // Text(item), data should appear here
        ],
      ),
    );
  }
}

使用onPress检索数据

2 个答案: