运行时出现问题时更改ListTile窗口小部件

Question

https://pub.dev/packages/table_calendar

我使用链接的软件包创建了日历。尝试在运行时更新ListTile的主要图像。 我试图将数据作为字符串发送，所以每个事件都必须有一个引人注目的字符串。我必须将数据类发送到下一页，它正在工作，但图像变量始终保持为空。希望有人可以解释为什么下面的setState函数不起作用。谢谢。

    class Calender extends StatefulWidget {
  @override
  _CalenderState createState() => _CalenderState();
}

class Data {
  String title, image, subText, subTitle;

  Data({this.image, this.title, this.subTitle, this.subText});
}

class _CalenderState extends State<Calender> with TickerProviderStateMixin {
  Map<DateTime, List> _events;
  List _selectedEvents, names;
  String image = " ";
  AnimationController _animationController;
  CalendarController _calendarController;

  @override
  void initState() {
    print("work");
    super.initState();
    final _selectedDay = DateTime.now();
    _calendarController = CalendarController();
    _events = {
      _selectedDay: [
        'TRY 1',
      ],
      _selectedDay.add(Duration(days: 15)): ['TRY 2'],
      _selectedDay.add(Duration(days: 20)): ['TTRY 3'],
    };

    _selectedEvents = _events[_selectedDay] ?? [];
    _animationController = AnimationController(
        vsync: this, duration: const Duration(milliseconds: 400));
  }

  @override
  void dispose() {
    _animationController.dispose();
    _calendarController.dispose();
    super.dispose();
  }

  void _onDaySelected(DateTime day, List events) {
    print('CALLBACK: _onDaySelected');
    setState(() {
      _selectedEvents = events;

      //working
    });
  }

  void _onVisibleDaysChanged(
      DateTime first, DateTime last, CalendarFormat format) {
    print('CALLBACK: _onVisibleDaysChanged');
  }

  void _onCalendarCreated(
      DateTime first, DateTime last, CalendarFormat format) {
    print('CALLBACK: _onCalendarCreated');
  }

  Data _data;

  Data get data {
    if (_data == null) {
      _data = Data();
    }
    return _data;
  }

  @override
  Widget build(BuildContext context) {
    names = _events.values.toList();
    //trying to  match strings with elements of list  here but not working
    setState(() {
      if (names[0] == 'TRY 1') {
        //image =
        image = 'https://www.w3schools.com/w3images/lights.jpg';
        //  'https://b.zmtcdn.com/data/pictures/5/18869335/85b9f0bc435132ec116846fafc335030.jpg';
        _data.subTitle = "8.01 PM door opening";
      }
      if (names[1] == 'TRY 2') {
        image =
            'https://cdn.pixabay.com/photo/2015/04/23/22/00/tree-736885__340.jpg';
        _data.subTitle = "8.02 PM door opening";
      }
      if (names[2] == 'TRY 3') {
        image =
            'https://previews.123rf.com/images/alexis84/alexis841404/alexis84140400557/27773925-planet-earth-and-blue-human-eye-elements-of-this-image-furnished-by-nasa-.jpg';
        _data.subTitle = "8.01 PM door opening";
      }
    });

    return SafeArea(
      child: Container(
        decoration: BoxDecoration(),
        child: Scaffold(
          body: Column(
              children: [
                _buildTableCalendar(),
                SizedBox(
                  height: 10,
                ),
                Expanded(
                  child: _buildEventList(image, data),
                )
              ],
            ),
          ),
        ),
 }

  Widget _buildTableCalendar() {
    return TableCalendar(
      calendarController: _calendarController,
      events: _events,
      startingDayOfWeek: StartingDayOfWeek.monday,
      calendarStyle: CalendarStyle(
        selectedColor: Colors.deepOrange[400],
        todayColor: Colors.deepOrange[200],
        markersColor: Colors.brown[700],
        outsideDaysVisible: false,
      ),
      headerStyle: HeaderStyle(
        formatButtonTextStyle:
            TextStyle().copyWith(color: Colors.white, fontSize: 15.0),
        formatButtonDecoration: BoxDecoration(
          color: Colors.deepOrange[400],
          borderRadius: BorderRadius.circular(16.0),
        ),
      ),
      onDaySelected: _onDaySelected,
      onVisibleDaysChanged: _onVisibleDaysChanged,
      onCalendarCreated: _onCalendarCreated,
    );
  }

  Widget _buildEventList(String image, Data data) {
    print(data.image);
    return ListView(
      children: _selectedEvents
          .map((event) => Container(
                decoration: BoxDecoration(
                  border: Border.all(width: 0.8),
                  borderRadius: BorderRadius.circular(12.0),
                ),
                margin:
                    const EdgeInsets.symmetric(horizontal: 8.0, vertical: 4.0),
                child: ListTile(
                  subtitle: Text("8 pm"),
                  leading: CircleAvatar(
                    //image comes here null
                    backgroundImage: NetworkImage(image),
                  ),
                  title: Text(event.toString()),
                  onTap: () {
                    setState(() {
                      if (event.toString() == "Beyond Akaretler") {
                        print("check1");
                        setState(() {
                          data.image =
                              "https://b.zmtcdn.com/data/pictures/5/18869335/85b9f0bc435132ec116846fafc335030.jpg";
                          data.title = "TRY1";
                        });
                      }
                      if (event.toString() == "Dorock XL") {
                        setState(() {
                          data.image =
                              "https://www.habervesaire.com/wp-content/uploads/2019/03/dorock-xl.jpg-1547825520-810x456.jpeg";
                          data.title = "TRY2 ";
                        });
                      }
                      if (event.toString() == "The Wall Kadıköy") {
                        setState(() {
                          data.image =
                              "https://b.zmtcdn.com/data/pictures/2/19165732/302d1418f06c81dca13e7c06bcc44ba9.jpg?fit=around|750:500&crop=750:500;*,*";
                          data.title = event.toString();
                        });
                      }
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (context) => EventPage(
                                    data: data,
                                  )));
                    });
                  },
                ),
              ))
          .toList(),
    );
  }
}

class EventPage extends StatelessWidget {
  final Data data;

  const EventPage({Key key, this.data}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Container(
      decoration: BoxDecoration(
          image: DecorationImage(
              image: NetworkImage("${data.image}"), fit: BoxFit.cover)),
      child: Scaffold(
        backgroundColor: Colors.transparent,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Text("${data.title}"),
        ),
      ),
    );
  }
}