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[英]Flutter: type 'Future<dynamic>' is not a subtype of type 'Widget'
[英]A dismissed Dismissible widget is still part of the tree in flutter
我有一个 todo 应用程序,它使用provider
进行 state 管理和sqlite
数据库。
在应用程序中,我尝试添加Dismissible
小部件以删除项目。
但问题是当我尝试删除项目时它确实从database
中删除但我在屏幕上出现错误。我是 flutter 的新手。
控制台中的错误。
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following assertion was thrown building Dismissible-[<'howll'>](dirty, dependencies: [Directionality], state: _DismissibleState#98163(tickers: tracking 2 tickers)):
A dismissed Dismissible widget is still part of the tree.
Make sure to implement the onDismissed handler and to immediately remove the Dismissible
widget from the application once that handler has fired.
User-created ancestor of the error-causing widget was:
TaskListTile file:///C:/Users/adity/Desktop/flutter-app/todoye/lib/widgets/task_list_view.dart:14:22
When the exception was thrown, this was the stack:
#0 _DismissibleState.build.<anonymous closure> (package:flutter/src/widgets/dismissible.dart:526:11)
#1 _DismissibleState.build (package:flutter/src/widgets/dismissible.dart:533:8)
#2 StatefulElement.build (package:flutter/src/widgets/framework.dart:4047:27)
#3 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3941:15)
#4 Element.rebuild (package:flutter/src/widgets/framework.dart:3738:5)
...
这是我的代码。
task_list_tile.dart
Dismissible(
key: Key(taskTitle),
onDismissed: (direction) {
deleteCallback();
Scaffold.of(context)
.showSnackBar(SnackBar(content: Text("$taskTitle removed.")));
},
child: ListTile(
title: Text(
'$taskTitle',
),
task_data.dart
void deleteTask(int id) {
taskDatabaseManager.deleteTask(id);
notifyListeners();
}
数据库连接.dart
Future<void> deleteTask(int id) async {
await openDb();
await _database.delete(
'tasks',
where: 'id = ?',
whereArgs: [id],
);
}
task_list_view.dart
class TaskListView extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Consumer<TaskData>(
builder: (context, taskData, child) {
return ListView.builder(
itemCount: taskData.taskCount,
itemBuilder: (context, index) {
return TaskListTile(
taskTitle: taskData.tasks[index].name,
isChecked: taskData.tasks[index].isDone,
checkboxCallback: (checkboxState) {
taskData.updateTask(taskData.tasks[index]);
},
deleteCallback: () {
taskData.deleteTask(taskData.tasks[index].id);
},
);
});
},
);
}
}
如果您确定您的可关闭小部件已被删除。 尝试修复key
。 密钥应该是唯一的。 如果任务的 id 是唯一的,
key: Key(taskData.tasks[index].id)
如果您没有任何其他恒定且唯一的数据,您可以尝试
key: UniqueKey()
当您关闭Dismissible
时,您应该将其从小部件树中删除。 在您的情况下,您为Dismissible
的每个项目显示taskData
,因此如果您关闭项目的Dismissible
,则应从列表中删除该项目。
因此,在deleteCallback
中,在执行deleteTask()
之后,您应该在setState()
中执行taskData.removeAt(index)
)。
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