颤振流生成器不会更新 Widget

Question

我正在使用TableCalender和Cloud Firestore创建一个日历屏幕。

我想在设置selectedEvent的位置为selectedEvent分配值后设置_buildEventList()，但是由于首先调用_buildEventList()，因此它将为空。 但是，在我设置了值之后，我调用了setState(){}.为什么屏幕不会更新？

final _firestore = Firestore.instance;
FirebaseUser loggedInUser;
// Example holidays
final Map<DateTime, List> _holidays = {
DateTime(2019, 1, 1): ['New Year's Day'],
DateTime(2019, 1, 6): ['Epiphany'],
DateTime(2019, 2, 14): ['Valentine's Day'],
DateTime(2019, 4, 21): ['Easter Sunday'],
DateTime(2019, 4, 22): ['Easter Monday'],
};
class CalenderScreen extends StatefulWidget {
@override
_CalenderScreenState createState() => _CalenderScreenState();
}
class _CalenderScreenState extends State<CalenderScreen>
with TickerProviderStateMixin {
DateTime _selectedDay;
Map<DateTime, List> _events = {};
Map<DateTime, List> _visibleEvents;
Map<DateTime, List> _visibleHolidays;
List _selectedEvents;
AnimationController _controller;
final _auth = FirebaseAuth.instance;
Widget streamBuilder;
Widget buildEvents;
@override
void initState() {
print("calender");
super.initState();
getCurrentUser();
_selectedDay = DateTime.now();
_selectedEvents = _events[_selectedDay] ?? [];
_visibleEvents = _events;
_visibleHolidays = _holidays;
_controller = AnimationController(
vsync: this,
duration: const Duration(milliseconds: 400),
);
_controller.forward();
}
void getCurrentUser() async {
try {
final user = await _auth.currentUser();
if (user != null) {
loggedInUser = user;
setStreamBuilder();
}
} catch (e) {
print(e);
}
}
void setStreamBuilder() {
setState(() {
streamBuilder = StreamBuilder<QuerySnapshot>(
stream: _firestore
.collection('users')
.document(loggedInUser.uid)
.collection('history')
.snapshots(),
builder: (context, snapshot) {
if (snapshot.data == null)
return Center(child: CircularProgressIndicator());
final historys = snapshot.data.documents;
_events = {};
for (var history in historys) {
DateTime timeStamp = history.data['date'].toDate();
DateTime currentDate =
DateTime(timeStamp.year, timeStamp.month, timeStamp.day);
if (_events.containsKey(currentDate)) {
_events[currentDate].add(history);
} else {
_events[currentDate] = [history];
}
}
print(_events);
DateTime now = DateTime.now();
_selectedDay = DateTime(now.year, now.month, now.day);
　　　　　　//here i set the _selectedEvents
_selectedEvents = _events[_selectedDay] ?? [];
_visibleEvents = _events;
return _buildTableCalendar();
},
);
});
}
void _onDaySelected(DateTime day, List events) {
setState(() {
_selectedDay = day;
_selectedEvents = events;
});
}
void _onVisibleDaysChanged(
DateTime first, DateTime last, CalendarFormat format) {
setState(() {
_visibleEvents = Map.fromEntries(
_events.entries.where(
(entry) =>
entry.key.isAfter(first.subtract(const Duration(days: 1))) &&
entry.key.isBefore(last.add(const Duration(days: 1))),
),
);
_visibleHolidays = Map.fromEntries(
_holidays.entries.where(
(entry) =>
entry.key.isAfter(first.subtract(const Duration(days: 1))) &&
entry.key.isBefore(last.add(const Duration(days: 1))),
),
);
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Color(0xFF232D3D),
body: Column(
mainAxisSize: MainAxisSize.max,
children: <Widget>[
streamBuilder != null
? streamBuilder
: Center(
child: CircularProgressIndicator(),
),
const SizedBox(height: 8.0),
_buildEventList()
],
),
floatingActionButton: FloatingPenButton(),
);
}
Widget _buildTableCalendar() {
return TableCalendar(
~~
);
}
Widget _buildEventList() {
print("bulid event");
return Expanded(
child: ListView(
children: _selectedEvents
.map(
(event) => HistoryCard(
history: HistoryData(
~~
),
)
.toList(),
),
);
}
}

Answer 1

这已经被看得足够多了，以至于我们都在经历/搜索同样的事情。 基本上，初始加载不会在流生成器首次加载时更新状态。 如果您单击并选择一天，那么它似乎加载正常并填充事件。 如果有人能建议为什么在默认情况下填充流时它不重建小部件，那将不胜感激。