我正在尝试从数据库中删除我的数据,并在成功后导航到我的主页。
以下是我的代码:
StatelessWidget
包含了一个 deleteFromDatabase
方法,该方法传递了一个 Id
(String) 和一个 context
:
Consumer<SettingsProvider>(
builder: (context, settingsProvider, child) {
final exerciseSettings = settingsProvider.findById(id);
if (exerciseSettings == null) {
return Center(
child: CircularProgressIndicator(),
);
}
return PreviewExerciseItem(
exerciseSettings: exerciseSettings,
id: id,
navigateToEdit: () =>
_navigateToEditPage(exerciseSettings, context),
deleteFromDatabase: () => _deleteFromDatabase(id, context),
navigateToCountDown: () =>
navigateToCountDownPage(exerciseSettings, context),
);
},
),
_deleteFromDatabase方法从StatelessWidget中调用,并显示AlertDialog以确认删除:
void _deleteFromDatabase(String id, context) async {
await showDialog(
context: context,
builder: (context) => new AlertDialog(
title: new Text("Are you sure you want to delete?"),
actions: <Widget>[
new FlatButton(
onPressed: () => Navigator.of(context).pop(false),
child: new Text('No'),
),
new FlatButton(
onPressed: () async {
try {
Navigator.of(context).pop(true);
await Provider.of<SettingsProvider>(context, listen: false)
.deleteFromList(id);
Navigator
.pushNamedAndRemoveUntil(context,HomePage.routeName, (Route route) => route.isFirst);
} catch (e) {
print(e);
}
},
child: new Text('Yes'),
),
],
),
);
}
我的提供程序类中的 deleteFromList 方法:
Future<void> deleteFromList(String id) async{
try{
final _itemIndex = _items.indexWhere((item) => item.id == id);
await _databaseHelper.deleteExercises(id);
_items.removeAt(_itemIndex);
notifyListeners();
}catch(e){
print(e);
}
}
Provider类中的findById:
CustomExercise findById(String id) {
return _items.firstWhere((prod) => prod.id == id);
}
注意:我已经成功从数据库中删除了我的数据,但就在它导航到我的主页之前,一个错误会以红色屏幕的形式出现并在一瞬间消失:Bad State: No Element。
以下是来自我的日志的完整错误消息:
正在构建 Consumer(dirty, dependencies: [_InheritedProviderScope, _InheritedTheme, _LocalizationsScope-[GlobalKey#5ce12]]) 时抛出以下 StateError: 坏状态:没有元素
相关的引起错误的小部件是:
Consumer<SettingsProvider>
当异常被抛出时,这是他的调用栈:
#0 ListMixin.firstWhere (dart:collection/list.dart:150:5)
#1 SettingsProvider.findById (package:workoutapp/providers/settings_provider.dart:12:19)
#2 PreviewExercisePage.build.<anonymous closure>
(package:workoutapp/pages/preview_exercise_page.dart:68:55)
#3 Consumer.buildWithChild (package:provider/src/consumer.dart:175:19)
#4 SingleChildStatelessWidget.build (package:nested/nested.dart:260:41)