如何将数据从 StatelessWidget 传递到 StatefulWidget

Question

请，我想传递数据（从 ItemList 到 StatefulWidget 中的 FloatingActionButton 的索引和列表）

class _mes_adresseState extends State<mes_adresse> {

  DatabaseHelper databaseHelper = new DatabaseHelper();

  _save(String token) async {
    final prefs = await SharedPreferences.getInstance();
    final key = 'token';
    final value = token;
    prefs.setString(key, value);
  }
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        floatingActionButton: FloatingActionButton.extended(
          backgroundColor: Colors.amber,
          onPressed: () {Navigator.of(context).push(
            new MaterialPageRoute(
                builder: (BuildContext context) => new EditAdress(
                      index: i // from index in list view.builder ,
                      list : list // from list in itemlist,
                )),

class ItemList extends StatelessWidget {
  List list;
  ItemList({this.list});

  @override
  Widget build(BuildContext context) {
    return new ListView.builder(
        itemCount: list[0] == null ? 0 : list[0].length,
        itemBuilder: (context, i) {
          return new Container(
            padding: const EdgeInsets.all(1.0),
            child: new GestureDetector(
              onTap: () => Navigator.of(context).push(
                new MaterialPageRoute(
                    builder: (BuildContext context) => new EditAdress(
                      list: list,
                      index: i,
                    )),
                //      builder: (BuildContext context) => new ShowData(list:list , index:i,) ),
              ),

      );},

floatingActionButton 返回另一个页面，并从页面 mes_adresse 列出和索引

Answer 1

你需要在目标类的构造函数中声明你的变量；

class EditAdress extends StatefulWidget {
  final List list;
  final int index;

  const EditAdress({Key key, this.list, this.index}) : super(key: key);
  @override
  _EditAdressState createState() => _EditAdressState();
}

class _EditAdressState extends State<EditAdress> {
  @override
  Widget build(BuildContext context) {
    // you can access your data through widget
    print(widget.index);    
    return Container(

    );
  }
}