Flutter：带自定义地图的下拉菜单

debugcn 发表于 Dev

丹妮

我这里有一张地图清单：

var taxesGroups = [
{
  "name": "Spain",
  "taxes": [
    {"name": "IVA", "percentage": "21"},
    {"name": "IRPF", "percentage": "19"},
  ]
},
{
  "name": "UK",
  "taxes": [
    {"name": "VAT", "percentage": "20"},
  ]
}
];

var dropdownValue = taxesGroups[0]["name"];

到目前为止，我已经尝试过了：

DropdownButton(
                  value: dropdownValue,
                  items: taxesGroups.map((taxGroup) {
                    return DropdownMenuItem<String>(
                      value: taxGroup["name"],
                      child: Text(taxGroup["name"]),
                    );
                  }).toList(),
                  onChanged: (taxGroup) {
                    setState(() {
                      dropdownValue = taxGroup;
                    });
                  },
                ),

我收到此错误：

类型“列表”不是类型“列表<DropdownMenuItem>”的子类型

我想这与我要在下拉菜单（英国，英国）中显示的信息以及选择一个选项后得到的信息有关，但我不知道

尼特什

您不匹配taxGroups地图。

我试图以此重新创建您的用例，并且它可以工作。

            class MyApp2 extends StatefulWidget {
              @override
              _MyAppState createState() => _MyAppState();
            }

            class _MyAppState extends State<MyApp2> {
              @override
              Widget build(BuildContext context) {
                return MaterialApp(
                  home: MyHomePage(),
                );
              }
            }

            class MyHomePage extends StatefulWidget {
              @override
              _MyHomePageState createState() => _MyHomePageState();
            }

            class _MyHomePageState extends State<MyHomePage> {
              var taxesGroups = [
                {
                  "name": "Spain",
                  "taxes": [
                    {"name": "IVA", "percentage": "21"},
                    {"name": "IRPF", "percentage": "19"},
                  ]
                },
                {
                  "name": "UK",
                  "taxes": [
                    {"name": "VAT", "percentage": "20"},
                  ]
                }
              ];

              var dropdownValue;

              @override
              void initState() {
                dropdownValue = taxesGroups[0];
                super.initState();
              }

              @override
              Widget build(BuildContext context) {
                return Scaffold(
                  appBar: AppBar(
                    title: Text("AppBar"),
                  ),
                  body: DropdownButton(
                    value: dropdownValue['name'],
                    items: taxesGroups.map((taxGroup) {
                      return DropdownMenuItem<String>(
                        value: taxGroup["name"],
                        child: Text(taxGroup["name"]),
                      );
                    }).toList(),
                    onChanged: (taxGroup) {
                      print('taxGroup $taxGroup');
                      taxesGroups.map((e) {
                        if (e["name"] == taxGroup)
                          setState(() {
                            dropdownValue = e;
                          });
                      });
                    },
                  ),
                );
              }
            }