【发布时间】：2020-12-03 20:06:51
【问题描述】：
我一直在尝试向我的待办事项列表添加一个编辑功能，用户可以在其中选择用户想要编辑的项目，然后应该会弹出一个对话框，其中有一个文本字段来输入所选的新值项目和保存更改的按钮。目前我有一个函数调用存储任务的数组，然后它应该使用索引触发所选项目，以便最后在 onPressed 时可以为所选值赋予一个新值，将此编辑功能视为 instagrams 之一，除了它编辑文本。
在对话框的编辑按钮中调用该函数时出现问题，因为我正在这样做 onPressed: () => _editToDoItem(_controller.text, index) 并且因为我必须在那里传递 2 个参数，所以我得到的错误是 Undefined name 'index'。如何解决此问题以使此编辑功能起作用？顺便说一句，由于这个错误，我还没有尝试编辑功能，所以如果功能或代码的任何部分不正确，请纠正我。
与下面的编辑功能有关。
List<ToDoElement> _toDoItems = [];
TextEditingController _controller = TextEditingController();
// this function adds a task to the list
void _addToDoItem(String task) {
if(task.isNotEmpty) {
setState(() {
_toDoItems.add(ToDoElement(task, DateTime.now()));
});
}
}
// this is the function that is supposed to edit the selected index from the _toDoItems array
void _editToDoItem(String newText, int index) {
setState(() {
_toDoItems[index].task = newText;
});
}
_editDialog(BuildContext context) {
return showDialog(context: context, builder: (context) {
return Dialog(
child: Container(
height: 180,
width: 100,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Container(
height: 60,
child: TextField(
controller: _controller,
autofocus: true,
style: TextStyle(fontSize: 18,),
)
),
Container(
height: 65,
width: double.infinity,
margin: EdgeInsets.only(top: 5,),
child: RaisedButton(
textColor: Colors.white,
color: Colors.red,
child: Text('EDIT'),
onPressed: () {
_editToDoItem(_controller.text, index); // error on index, Undefined name 'index'
FocusScope.of(context).requestFocus(FocusNode());
},
),
),
],
),
),
);
});
}
完整的 main.dart 文件
class ToDoElement {
String task;
final DateTime timeOfCreation;
ToDoElement(this.task, this.timeOfCreation);
}
void main() => runApp(MaterialApp(home: MyApp()));
class MyApp extends StatefulWidget {
@override
createState() => MyAppState();
}
class MyAppState extends State<MyApp> {
List<ToDoElement> _toDoItems = [];
TextEditingController _controller = TextEditingController();
void _addToDoItem(String task) {
if(task.isNotEmpty) {
setState(() {
_toDoItems.add(ToDoElement(task, DateTime.now()));
});
}
}
void _editToDoItem(String newText, int index) {
setState(() {
_toDoItems[index].task = newText;
});
}
void _removeTodoItem(int index) {
setState(() => _toDoItems.removeAt(index));
}
_editDialog(BuildContext context) {
return showDialog(context: context, builder: (context) {
return Dialog(
backgroundColor: Colors.transparent,
child: Container(
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.all(Radius.circular(20.0)),
),
padding: EdgeInsets.all(20),
height: 180,
width: 100,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Container(
height: 60,
child: TextField(
controller: _controller,
autofocus: true,
/*onSubmitted: (val) {
_addToDoItem(val);
_controller.clear();
},*/
style: TextStyle(fontSize: 18,),
decoration: InputDecoration(
hintText: 'Add a task here...',
enabledBorder: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(12.0)),
borderSide: BorderSide(color: Colors.red, width: 2),
),
focusedBorder: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(12.0)),
borderSide: BorderSide(color: Colors.red, width: 2),
),
),
)
),
Container(
height: 65,
width: double.infinity,
margin: EdgeInsets.only(top: 5,),
child: RaisedButton(
textColor: Colors.white,
color: Colors.red,
child: Text('EDIT', style: TextStyle(fontSize: 18)),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(12)),
),
onPressed: () {
_editToDoItem(_controller.text, index);
FocusScope.of(context).requestFocus(FocusNode());
},
),
),
],
),
),
);
});
}
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: () => null,
),
),
FlatButton(
child: Text('Edit', style: TextStyle(color: Colors.red, fontSize: 16.5),),
onPressed: () => _editDialog(context),
),
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) {
if (index < _toDoItems.length) {
return _buildToDoItem(_toDoItems[index].task, index);
}
},
),
);
}
@override
Widget build(BuildContext context) {
return 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: GestureDetector(
onTap: () {
FocusScope.of(context).requestFocus(FocusNode());
},
child: 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,),
decoration: InputDecoration(
hintText: 'Add a task here...',
enabledBorder: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(12.0)),
borderSide: BorderSide(color: Colors.red, width: 2),
),
focusedBorder: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(12.0)),
borderSide: BorderSide(color: Colors.red, width: 2),
),
),
),
),
),
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()
]
),
),
);
}
}
如果您有任何问题，请在 cmets 中告诉我；）
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标签： flutter dart flutter-layout