问题描述
更改设备方向时出现以下错误：
E/Flutter (31741): [ERROR:Flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: setState() called after dispose(): _StreamBuilderBaseState<List<ScheduledActivity>,AsyncSnapshot<List<ScheduledActivity>>>#afadb(lifecycle state: defunct,not mounted)
E/Flutter (31741): This error happens if you call setState() on a State object for a widget that no longer appears in the widget tree (e.g.,whose parent widget no longer includes the widget in its build). This error can occur when code calls setState() from a timer or an animation callback.
E/Flutter (31741): The preferred solution is to cancel the timer or stop listening to the animation in the dispose() callback. Another solution is to check the "mounted" property of this object before calling setState() to ensure the object is still in the tree.
E/Flutter (31741): This error might indicate a memory leak if setState() is being called because another object is retaining a reference to this State object after it has been removed from the tree. To avoid memory leaks,consider breaking the reference to this object during dispose().
E/Flutter (31741): #0 State.setState.<anonymous closure> (package:Flutter/src/widgets/framework.dart:1204:9)
E/Flutter (31741): #1 State.setState (package:Flutter/src/widgets/framework.dart:1239:6)
E/Flutter (31741): #2 _StreamBuilderBaseState._subscribe.<anonymous closure> (package:Flutter/src/widgets/async.dart:140:9)
E/Flutter (31741): #3 _StartWithValueStream.listen.<anonymous closure> (package:moor/src/utils/start_with_value_transformer.dart:49:17)
E/Flutter (31741): #4 _rootRun (dart:async/zone.dart:1182:47)
E/Flutter (31741): #5 _CustomZone.run (dart:async/zone.dart:1093:19)
E/Flutter (31741): #6 _CustomZone.runGuarded (dart:async/zone.dart:997:7)
E/Flutter (31741): #7 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1037:23)
E/Flutter (31741): #8 _rootRun (dart:async/zone.dart:1190:13)
E/Flutter (31741): #9 _CustomZone.run (dart:async/zone.dart:1093:19)
E/Flutter (31741): #10 _CustomZone.runGuarded (dart:async/zone.dart:997:7)
E/Flutter (31741): #11 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1037:23)
E/Flutter (31741): #12 _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
E/Flutter (31741): #13 _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
E/Flutter (31741):
现在，我知道了about the if (mounted) setState fix-事情是，我没有在应用中使用setState，因为我正在使用bloclibrary。
此外，查看错误，我可以看到StreamBuilder<List<ScheduledActivity>>，这是导致以下问题的以下代码片段的唯一线索：
...
@override
Widget build(BuildContext context) {
return StreamBuilder<List<ScheduledActivity>>(
stream: RepositoryProvider.of<AppDatabase>(context)
.scheduledActivitiesDao
.watchActivitiesByPlant(widget.plantId),builder: (context,snapshot) {
if (snapshot.hasError) print('>>>> DB error - ${snapshot.error}');
if (!snapshot.hasData) return ProgressIndicatorWidget();
return Text('items = ${snapshot.data.length}');
},);
}
...
上述代码的两个注释：
解决方法
问题似乎与事实有关，我每次调用Stream方法时都在创建build。
如何重构代码：
- 添加
Stream<List<ScheduledActivity>> _stream; - 在此处设置其值：
@override
void didChangeDependencies() {
super.didChangeDependencies();
_stream = RepositoryProvider.of<AppDatabase>(context)
.scheduledActivitiesDao
.watchActivitiesByPlant(widget.plantId);
}
- 替换
RepositoryProvider.of<AppDatabase>context).scheduledActivitiesDao.watchActivitiesByPlant( widget.plantId),
与
stream: _stream,