[英]Flutter:1 positional argument(s) expected, but 0 found
I am working on a flutter project, which separated the body: widget from the main.dart and placed it inside a new statefull widget with the file name todu_list.dart now i am trying to call it back to main.dart file body: SingleChildScrollView(child: Lists()),
並收到此錯誤
1 positional argument(s) expected, but 0 found.
Try adding the missing arguments.
我在 StackOverFlow 上經歷了很多類似的問題,並意識到我應該在括號“()”內添加一個參數,但我不知道我的列表小部件中的哪個 function 我應該在那里調用
下面是“列表”小部件代碼
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import '../models/todus.dart';
import 'package:intl/intl.dart';
import 'package:sqflite/sqflite.dart';
import '../models/database_helper.dart';
class Lists extends StatefulWidget {
final Function addTx;
Lists(this.addTx);
@override
_ListsState createState() => _ListsState();
}
class _ListsState extends State<Lists> {
final dbHelper = DatabaseHelper.instance;
void _addNewTransaction(BuildContextcontext) {
showModalBottomSheet(
backgroundColor: Colors.white,
isScrollControlled: true,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.vertical(top: Radius.circular(25.0))),
context: context,
builder: (_) {
return GestureDetector(
onTap: () {},
// Where i started the code pasting from
child: Padding(
padding: MediaQuery.of(context).viewInsets,
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Card(
elevation: 0.000,
child: Container(
padding: EdgeInsets.all(20),
child: Column(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TextField(
decoration: InputDecoration(labelText: 'Title'),
controller: _titleController,
autofocus: true,
onSubmitted: null,
// onChanged: (val) {
// titleInput = val;
// },
),
TextField(
decoration: InputDecoration(labelText: 'Description'),
controller: _discriptionController,
onSubmitted: null,
// onChanged: (val) => amountInput = val,
),
Container(
height: 70,
child: Row(
children: [
Text(selectedDateAndTime == null
? 'No Date Choosen'
: DateFormat('MM/dd/yyyy HH:mm')
.format(selectedDateAndTime)
// : DateFormat.yMd()
// .format(_selectedDate),
),
FlatButton(
textColor: Theme.of(context).primaryColor,
child: Icon(Icons.calendar_today),
// onPressed: () async {
// var value = await _selectedTime();
// },
onPressed: () => _selectDayAndTimeL(context),
),
],
),
),
RaisedButton(
child: Text('Save Todo'),
color: Theme.of(context).primaryColor,
textColor: Theme.of(context).textTheme.button.color,
onPressed: _submitData,
),
],
),
),
),
),
),
);
},
);
}
final _titleController = TextEditingController();
final _discriptionController = TextEditingController();
var favorite;
// DateTime _selectedDate;
DateTime selectedDateAndTime;
@override
void dispose() {
super.dispose();
_discriptionController.dispose();
_titleController.dispose();
}
Future _selectDayAndTimeL(BuildContext context) async {
DateTime _selectedDay = await showDatePicker(
context: context,
initialDate: DateTime.now(),
firstDate: DateTime(2021),
lastDate: DateTime(2030),
builder: (BuildContext context, Widget child) => child);
TimeOfDay _selectedTime = await showTimePicker(
context: context,
initialTime: TimeOfDay.now(),
);
if (_selectedDay != null && _selectedTime != null) {
//a little check
}
setState(() {
selectedDateAndTime = DateTime(
_selectedDay.year,
_selectedDay.month,
_selectedDay.day,
_selectedTime.hour,
_selectedTime.minute,
);
// _selectedDate = _selectedDay;
});
// print('...');
}
List<ItemLists> items = [
ItemLists(
title: 'Best Music of the Year',
description: 'Davido',
favorite: false,
),
ItemLists(
title: 'Best Album Cover design',
description: 'Brighter Press',
favorite: false,
),
void _submitData() {
// if (_amountController.text.isEmpty) {
// return;
// }
final enteredTitle = _titleController.text;
final enteredDescription = _discriptionController.text;
if (enteredTitle.isEmpty) {
return;
}
widget.addTx(
enteredTitle,
enteredDescription,
selectedDateAndTime,
);
Navigator.of(context).pop();
}
@override
Widget build(BuildContext context) {
return SizedBox(
child: Container(
child: ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemBuilder: (context, index) {
return Dismissible(
key: ObjectKey(items[index]),
background: Container(
color: Colors.red,
),
child: Card(
child: ListTile(
leading: new IconButton(
icon: Icon(
Icons.check,
color:
items[index].favorite ? Colors.green : Colors.grey,
),
tooltip: 'Add to Favorite',
onPressed: () {
setState(() {
items[index].favorite = !items[index].favorite;
});
}),
title: Text('${items[index].title}'),
subtitle: Text('${items[index].description}'),
trailing: IconButton(
icon: Icon(Icons.calendar_today),
onPressed: () => _selectDayAndTimeL(context),
),
)),
onDismissed: (direction) {
final String myTitle = items[index].title;
// Remove the item from the data source.
setState(() {
var deletedItems = items.removeAt(index);
Scaffold.of(context).showSnackBar(
SnackBar(
content: Text('$myTitle Deleted'),
action: SnackBarAction(
label: 'Undo',
onPressed: () => setState(
() => items.insert(index, deletedItems),
)),
),
);
});
});
},
itemCount: items.length,
),
),
);
floatingActionButton:
FloatingActionButton(
child: Icon(Icons.add),
onPressed: () => _addNewTransaction(context),
backgroundColor: Colors.redAccent,
);
}
}
您必須提供 function 作為參數才能構建您的小部件。 這不是您將要調用的小部件的 function,而是您將從列表小部件中調用的 function addTx。
要么刪除參數,要么傳遞一個 function 來解決它。
示例:由於您的 function 預計有 3 個參數:
widget.addTx(
enteredTitle,
enteredDescription,
selectedDateAndTime,
);
您可以創建:
void addTitleDescDate(string title, string description, string date) { // NB you should probably use a Date object or epoch time.
print(title);
print(description);
print(date);
}
你使用這個 function Lists(addTitleDescDate)
作為旁注,我真的不明白將這個 function 作為共享給 Lists 小部件的參數的意義,但是如果您想了解有關 function 作為參數的更多信息,那仍然很有趣。
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