我正在开发一个关于 flutter 的待办事项列表应用程序，我想按日期对上传的任务进行排序(新任务首先出现)。为此，我认为应该为待办事项列表中的每个上传项目提供一个 key ，并且该 key 应包含一个日期。为了做到这一点，我在一个按日期排序的平面列表中的数据中添加了一个函数，但由于我是新来的，所以我不知道该怎么做。任何想法都有帮助:)
主要.dart
List<String> _toDoItems = []; //this is the array in which the uploaded tasks are stored, btw Im not using any database.
TextEditingController _controller = TextEditingController();
void _addToDoItem(String task) {
if(task.length > 0) {
setState(() {
_toDoItems.add(task);
});
}
}
void _removeTodoItem(int index) {
setState(() => _toDoItems.removeAt(index));
}
Widget _buildToDoItem(String toDoText, int index) {
return SizedBox(
child: Container(
height: 58,
margin: EdgeInsets.only(left: 22.0, right: 22.0, bottom: 12,),
decoration: BoxDecoration(
border: Border.all(width: 1.5, color: Colors.red),
borderRadius: BorderRadius.all(Radius.circular(18)),
),
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children:[
Expanded(
child: ListTile(
title: Text(
toDoText,
style: TextStyle(fontSize: 18),
),
onTap: () => _removeTodoItem(index),
),
),
FlatButton(
child: Text('Delete', style: TextStyle(color: Colors.red, fontSize: 16.5),),
onPressed: () => _removeTodoItem(index),
),
],
),
),
);
}
Widget _buildToDoList() {
return Expanded(
child: ListView.builder(
itemBuilder: (context, index) {
if (index < _toDoItems.length) {
return _buildToDoItem(_toDoItems[index], index);
}
},
),
);
}
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(50),
child: AppBar(
centerTitle: true,
backgroundColor: Colors.red,
title: Text('To Do List', style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold,),),
)
),
backgroundColor: Colors.white,
body: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
height: 60,
margin: EdgeInsets.all(22),
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Expanded(
flex: 10,
child: Container(
height: double.infinity,
child: TextField(
controller: _controller,
autofocus: true,
onSubmitted: (val) {
_addToDoItem(val);
_controller.clear();
},
style: TextStyle(fontSize: 18,),
),
),
),
Expanded(
flex: 4,
child: Container(
height: double.infinity,
margin: EdgeInsets.only(left: 12),
child: RaisedButton(
textColor: Colors.white,
color: Colors.red,
child: Text('ADD', style: TextStyle(fontSize: 18)),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(12)),
),
onPressed: () {
_addToDoItem(_controller.text);
_controller.clear();
FocusScope.of(context).requestFocus(FocusNode());
},
),
),
),
],
),
),
_buildToDoList()
]
),
),
);
}
最佳答案
您需要使用 sort() List 的方法，您还需要能够以某种方式存储创建任务的时间。
我用你发布的代码做了一个例子。使用它，您最后创建的元素将始终是列表的第一个。
import 'package:flutter/material.dart';
class ToDoElement {
final String task;
final DateTime timeOfCreation;
ToDoElement(this.task, this.timeOfCreation);
}
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
@override
createState() => _MyAppState();
}
class _MyAppState extends State {
TextEditingController _controller = TextEditingController();
List<ToDoElement> _toDoItems = [];
void _removeTodoItem(int index) {
setState(() => _toDoItems.removeAt(index));
}
void _addToDoItem(String task) {
if (task.isNotEmpty) {
setState(() => _toDoItems.add(ToDoElement(task, DateTime.now())));
}
}
Widget _buildToDoItem(String toDoText, int index) {
return SizedBox(
child: Container(
height: 58,
margin: EdgeInsets.only(left: 22, right: 22, bottom: 12),
decoration: BoxDecoration(
border: Border.all(width: 1.5, color: Colors.red),
borderRadius: BorderRadius.all(Radius.circular(18)),
),
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Expanded(
child: ListTile(
title: Text(
toDoText,
style: TextStyle(fontSize: 18),
),
onTap: () => _removeTodoItem(index),
),
),
FlatButton(
child: Text(
'Delete',
style: TextStyle(color: Colors.red, fontSize: 16.5),
),
onPressed: () => _removeTodoItem(index),
),
],
),
),
);
}
int compareElement(ToDoElement a, ToDoElement b) =>
a.timeOfCreation.isAfter(b.timeOfCreation) ? -1 : 1;
Widget _buildToDoList() {
_toDoItems.sort(compareElement);
return Expanded(
child: ListView.builder(
itemCount: _toDoItems.length,
itemBuilder: (context, index) {
return _buildToDoItem(_toDoItems[index].task, index);
},
),
);
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(50),
child: AppBar(
centerTitle: true,
backgroundColor: Colors.red,
title: Text(
'To Do List',
style: TextStyle(
fontSize: 24,
fontWeight: FontWeight.bold,
),
),
)),
backgroundColor: Colors.white,
body: Column(crossAxisAlignment: CrossAxisAlignment.center, children: [
Container(
height: 60,
margin: EdgeInsets.all(22),
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Expanded(
flex: 10,
child: Container(
height: double.infinity,
child: TextField(
controller: _controller,
autofocus: true,
onSubmitted: (val) {
_addToDoItem(val);
_controller.clear();
},
style: TextStyle(
fontSize: 18,
),
),
),
),
Expanded(
flex: 4,
child: Container(
height: double.infinity,
margin: EdgeInsets.only(left: 12),
child: RaisedButton(
textColor: Colors.white,
color: Colors.red,
child: Text('ADD', style: TextStyle(fontSize: 18)),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(12)),
),
onPressed: () {
_addToDoItem(_controller.text);
_controller.clear();
FocusScope.of(context).requestFocus(FocusNode());
},
),
),
),
],
),
),
_buildToDoList()
]),
),
);
}
}
关于flutter - 如何在 flutter 中按日期动态排序？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/63380065/