Flutter将类添加到由未来构建器构建的窗口小部件

Question

我帮助构建了这个动态扩展文件，现在我正在尝试添加一个传递给onTap的类，以便它可以传递给另一个页面。我已经尝试了几件事并继续犯这个错误。如果我没有向onTap上添加任何内容，那么函数调用全部工作但没有数据可以传递。

任何指导都会很棒。

我收到此错误：

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:http/http.dart' as http;
import 'package:cswauthapp/models.dart';
import 'package:cswauthapp/FacPage.dart';
import 'package:cswauthapp/ReasonPage.dart';

import 'dart:convert';


class SpecPage extends StatefulWidget {
  SpecPage({Key key, this.spec}) : super(key: key);

  final Specialties spec;

  //final Facilities fac;
  //static const String routeName = "/specs/spec";

  @override
  _SpecPageState createState() => new _SpecPageState();
}

class _SpecPageState extends State<SpecPage> {
  Future<http.Response> _responseFuture;

  bool _authenticated = false;
  bool _dataReceived = false;
  SharedPreferences prefs;
  List myReasonlist;
  int listcount = 0;
  int specid;

  @override
  void initState() {
    super.initState();
    _responseFuture = http.get('http://$baseurl:8080/support/dc/${widget.spec.id}');

    _getPrefs();
    //_getSpecialty();
    //_getFacilities();
  }

  _getPrefs() async {
    prefs = await SharedPreferences.getInstance();
    _authenticated = prefs.getBool('authenticated');
    print('AUTH3: ' + _authenticated.toString());
    print('AUTHCODE3: ' + prefs.getString('authcode'));
    prefs.setInt('specid', widget.spec.id);
    print('SPECID: ' + prefs.getInt('specid').toString());
    specid = await prefs.getInt('specid');
    _getReasons();
  }

  var jsonCodec = const JsonCodec();

  _getReasons() async {
    var _url = 'http://$baseurl:8080/support/getreferralreasons/$specid';

    var http = createHttpClient();
    var response = await http.get(_url);

    var reasons = await jsonCodec.decode(response.body);

    myReasonlist = await reasons.toList();
    //_dataReceived = true;

    if (mounted) {
      setState(() {
        _dataReceived = true;
        listcount = myReasonlist.length;
      });
    }
  }

  Future<Null> _onRefresh() {
    Completer<Null> completer = new Completer<Null>();
    Timer timer = new Timer(new Duration(seconds: 3), () {
      completer.complete();
    });
    return completer.future;
  }


  @override
  Widget build(BuildContext context) {
    var _children = <Widget>[

      new Center(
        child: new Container(
          padding: new EdgeInsets.only(
              left: 10.0, right: 10.0, top: 20.0, bottom: 10.0),
          child: new Text('Referral Reasons for '+widget.spec.name,
            style: new TextStyle(fontSize: 30.0),
            textAlign: TextAlign.center,
          ),
        ),
      ),

      new Expanded(
          child: new FutureBuilder(
            future: _responseFuture,
            builder: (BuildContext context, AsyncSnapshot<http.Response> response) {
              if (!response.hasData) {
                return const Center(
                  child: const Text('Loading...'),
                );
              } else if (response.data.statusCode != 200) {
                return const Center(
                  child: const Text('Error loading data'),
                );
              } else {
                List<dynamic> json = JSON.decode(response.data.body);
                return new MyExpansionTileList(json);
              }
            },
          ),

      ),

      /*new Expanded(
        flex: 1,
        child: new RefreshIndicator(
          child: new ListView.builder(
            itemBuilder: _itemBuilder,
            itemCount: listcount,
          ),
          onRefresh: _onRefresh,

        ),
      ),*/

    ];
    return new Scaffold(
      appBar: new AppBar(title: new Text("My Specialty")),
      body: new Column(
        children: _children,
      ),
    );
  }

  /*Widget _itemBuilder(BuildContext context, int index) {
    Reasons reason = getReason(index);
    return new ReasonWidget(reason: reason,);
  }*/

  Reasons getReason(int index) {
    return new Reasons(
        myReasonlist[index]['rid'],
        myReasonlist[index]['reason'],
        myReasonlist[index]['sid'],
        myReasonlist[index]['specname']
    );
    //return new Specialties.fromMap(mylist[index]);

  }
}

class MyExpansionTileList extends StatelessWidget {
  final List<dynamic> elementList;

  MyExpansionTileList(this.elementList);

  List<Widget> _getChildren() {
    List<Widget> children = [];
    elementList.forEach((element) {
      children.add(
        new MyExpansionTile(element['did'], element['dname']),
      );
    });
    return children;
  }

  @override
  Widget build(BuildContext context) {
    return new ListView(
      children: _getChildren(),
    );
  }
}

class MyExpansionTile extends StatefulWidget {
  final int did;
  final String name;

  MyExpansionTile(this.did, this.name);
  @override
  State createState() => new MyExpansionTileState();
}

class MyExpansionTileState extends State<MyExpansionTile> {
  PageStorageKey _key;
  Future<http.Response> _responseFuture;
  List<Widget> reasonList;
  List reasList;
  //Reasons reason;

  @override
  void initState() {
    super.initState();
    _responseFuture =
        http.get('http://$baseurl:8080/support/dcreasons/${widget.did}');
  }

  @override
  Widget build(BuildContext context) {
    _key = new PageStorageKey('${widget.did}');
    return new ExpansionTile(
      key: _key,
      title: new Text(widget.name,
        style: new TextStyle(fontWeight: FontWeight.bold),
      ),
      children: <Widget>[
        new FutureBuilder(
          future: _responseFuture,
          builder:
              (BuildContext context, AsyncSnapshot<http.Response> response) {
            if (!response.hasData) {
              return const Center(
                child: const Text('Loading...'),
              );
            } else if (response.data.statusCode != 200) {
              return const Center(
                child: const Text('Error loading data'),
              );
            } else {
              List<dynamic> json = JSON.decode(response.data.body);
              reasonList = [];
              json.forEach((element) {

                reasonList.add(new ListTile(
                  dense: true,
                  title: new Text(element['reason']),
                  onTap: _onTap(new Reasons(element['rid'], element['reason'], element['sid'], element['specname'])),
                ));
              });
              //reasList = json.toList();
              return new Column(children: reasonList);
            }

          },

        )
      ],
    );
  }

  _onTap(Reasons reason) {
    Route route = new MaterialPageRoute(
      settings: new RouteSettings(name: "/reasons/reason"),
      builder: (BuildContext context) => new ReasonPage(reason: reason),
    );
    Navigator.of(context).push(route);
  }
}

我试图在循环json的过程中在ExpansionTile小部件下运行此代码，我将元素添加到_onTap函数，并尝试构建类并将类添加到_onTap并继续错误。没有它，它工作正常，但我需要在另一页上的数据。任何想法都会很棒，我确信我会因为我刚接触其他语言而感到愚蠢。

@OnDelete

Answer 1

我想出来了，不知道为什么，但我做了内联方法并且它有效。

@override
  Widget build(BuildContext context) {
    _key = new PageStorageKey('${widget.did}');
    return new ExpansionTile(
      key: _key,
      title: new Text(widget.name,
        style: new TextStyle(fontWeight: FontWeight.bold),
      ),
      children: <Widget>[
        new FutureBuilder(
          future: _responseFuture,
          builder:
              (BuildContext context, AsyncSnapshot<http.Response> response) {
            if (!response.hasData) {
              return const Center(
                child: const Text('Loading...'),
              );
            } else if (response.data.statusCode != 200) {
              return const Center(
                child: const Text('Error loading data'),
              );
            } else {
              List<dynamic> json = JSON.decode(response.data.body);
              reasonList = [];
              json.forEach((element) {

                reasonList.add(new ListTile(
                  dense: true,
                  leading: new Text(' - '),
                  title: new Text(element['reason']),
                  //HERE IS WHERE I FIXED IT.
                  onTap: () {
                    Route route = new MaterialPageRoute(
                      settings: new RouteSettings(name: "/reasons/reason"),
                      builder: (BuildContext context) => new ReasonPage(id: element['rid'], reason: element['reason'], sid: element['sid']),
                    );
                    Navigator.of(context).push(route);
                  },
                ));
              });
              //reasList = json.toList();
              return new Column(children: reasonList);
            }

          },

        )
      ],
    );
  }