如何在 Flutter DropDown 按钮中搜索

Question

我在本地 json 中有一个国家名称列表。我可以加载我的本地 json 并分配给DropDown button。json 文件中有 193 个国家/地区，例如。如下所示。如果我想选择美国，用户必须一直向下滚动。如何输入国家名称，例如；如果我用户输入 U 或 u，下拉菜单可以进行快速过滤并列出所有以 U 开头的国家/地区，例如美国。如何在 Flutter DropDownbutton 项目中搜索？

{
    "country": [
            {
                "countryCode": "AD",
                "countryName": "Andorra",
                "currencyCode": "EUR",
                "isoNumeric": "020"
            },
            {
                "countryCode": "AE",
                "countryName": "United Arab Emirates",
                "currencyCode": "AED",
                "isoNumeric": "784"
            },
            {
                "countryCode": "AF",
                "countryName": "Afghanistan",
                "currencyCode": "AFN",
                "isoNumeric": "004"
            },

Answer 1

You can use searchable_dropdown package instead: https://pub.dev/packages/searchable_dropdown

And here is my example code searchable_dropdown dont work with class list

Make sure that you put the following if you use a class list like my example

  @override
  String toString() {
    return this.key;
  }

Answer 2

一种方法是使用 aTextEditingController来过滤您的内容，ListView如下所示：

class YourPage extends StatefulWidget {
  @override
  State createState() => YourPageState();
}

class YourPageState extends State<YourPage> {
  List<Country> countries = new List<Country>();
  TextEditingController controller = new TextEditingController();
  String filter;

  @override
  void initState() {
    super.initState();
    //fill countries with objects
    controller.addListener(() {
      setState(() {
        filter = controller.text;
      });
    });
  }

  @override
  void dispose() {
    super.dispose();
    controller.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Material(
        color: Colors.transparent,
        child: new Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: <Widget>[
            new Padding(
                padding: new EdgeInsets.only(top: 8.0, left: 16.0, right: 16.0),
                child: new TextField(
                  style: new TextStyle(fontSize: 18.0, color: Colors.black),
                  decoration: InputDecoration(
                    prefixIcon: new Icon(Icons.search),
                    suffixIcon: new IconButton(
                      icon: new Icon(Icons.close),
                      onPressed: () {
                        controller.clear();
                        FocusScope.of(context).requestFocus(new FocusNode());
                      },
                    ),
                    hintText: "Search...",
                  ),
                  controller: controller,
                )),
            new Expanded(
              child: new Padding(
                  padding: new EdgeInsets.only(top: 8.0),
                  child: _buildListView()),
            )
          ],
        ));
  }

  Widget _buildListView() {
    return ListView.builder(
        itemCount: countries.length,
        itemBuilder: (BuildContext context, int index) {
          if (filter == null || filter == "") {
            return _buildRow(countries[index]);
          } else {
            if (countries[index].countryName
                .toLowerCase()
                .contains(filter.toLowerCase())) {
              return _buildRow(countries[index]);
            } else {
              return new Container();
            }
          }
        });
  }

  Widget _buildRow(Country c) {
    return new ListTile(
        title: new Text(
          c.countryName,
        ),
        subtitle: new Text(
          c.countryCode,
        ));
  }
}