我无法使 DropDownButton 发挥作用...有什么方法可以帮助我

Question

Scaffold(
      appBar: MyAppBar(),
      body: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 32.0),
        child: ListView(
          children: [
            Row(
              children: [
                Text('Total balance'),
                addWidth(3),
                Icon(
                  Icons.info_outline,
                  size: 17,
                ),
                const Spacer(),
                DropdownButton<String>(
                    value: 'View other balances',
                    items: [
                      DropdownMenuItem(
                        value: 'lol',
                        child: Text('lol'),
                      )
                    ],
                    onChanged: (value) {})
              ],
            )
          ],
        ),
      ),
    );

请问下拉按钮可能有什么问题

它给了我错误，我没想到

Answer 1

您很可能想要这样的东西：

class Home extends StatefulWidget {
  const Home({super.key});

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  String? selectedValue;

  final List<DropdownMenuItem<String>> items = const [
    DropdownMenuItem(value: 'lol', child: Text('lol'),),
    DropdownMenuItem(value: 'lol2', child: Text('lol2'),),
    DropdownMenuItem(value: 'lol3', child: Text('lol3'),),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: MyAppBar(),
      body: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 32.0),
        child: ListView(
          children: [
            Row(
              children: [
                Text('Total balance'),
                addWidth(3),
                Icon(Icons.info_outline, size: 17,),
                const Spacer(),
                DropdownButton<String>(
                  value: selectedValue,
                  items: items,
                  onChanged: (value) {
                    setState(() => selectedValue = value);
                  }
                )
              ],
            )
          ],
        ),
      ),
    );
  }
}

与

value

匹配列表中的一项。