我想在Flutter中使列表成为可重新排序，但是我已经拥有Future Builder和List View。 ReorderableListView 应该是其他ListView的父项还是子项？ 如何为此初始化密钥？
return Scaffold(
body: Container(
child: ListView(
children: <Widget>[
SizedBox(
height: MediaQuery.of(context).size.height * 0.882,
child: FutureBuilder(
future: databaseHelper.getNoteList(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Text('Loading');
} else {
if (snapshot.data.length < 1) {
return Center(
child: Text('No Messages, Create New one'),
);
}
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int i) {
return Column(
children: <Widget>[
ListTile(
title: Text(snapshot.data[i].title),
),
subtitle:
Text(snapshot.data[i].note, maxLines: 4),
onTap: () {},
),
Divider(color: Theme.of(context).accentColor)
],
);
},
);
}
},
),
)
],
),
),
);
我尝试添加ReorderableListView，但是由于子级：[]不可能，我不知道在哪里为“ i”放置for循环
future: databaseHelper.getNoteList(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Text('Loading');
} else {
if (snapshot.data.length < 1) {
return Center(
child: Text('No Messages, Create New one'),
);
}
return ReorderableListView(
children: List.generate(
snapshot.data.length,
(index) {
return ListTile(
key: Key('$index'),
title: Text(
snapshot.data[i].title,
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 20,
),
),
subtitle:
Text(snapshot.data[i].note, maxLines: 4),
trailing: InkWell(
child: Icon(Icons.check, color: Colors.green),
onTap: () {
TextEditingController txt =
TextEditingController();
txt.text = snapshot.data[i].note;
print(txt);
Route route = MaterialPageRoute(
builder: (context) =>
MyHomePage(custMessage: txt));
Navigator.push(context, route);
// addNewMessageDialog(txt);
},
),
isThreeLine: true,
onTap: () {
Route route = MaterialPageRoute(
builder: (context) => AddNote(
note: snapshot.data[i],
));
Navigator.push(context, route);
},
);
},
).toList()
//Divider(color: Theme.of(context).accentColor),
);
}
})```
Right now the error is undefined variable i.
答案 0 :(得分：0)
我有办法解决它。
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基本上，使用List.generate和索引来遍历数据库元素。这样，我可以使用将来的构建器来显示数据库中的元素，而不是普通列表并对该列表重新排序。
```Widget build(BuildContext context) {
databaseHelper.initlizeDatabase();
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.green,
title: Text('Notes'),
),
body: Container(
padding: EdgeInsets.all(8.0),
child: ListView(
children: <Widget>[
SizedBox(
height: MediaQuery.of(context).size.height * 0.882,
child: FutureBuilder(
future: databaseHelper.getNoteList(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Text('Loading');
} else {
if (snapshot.data.length < 1) {
return Center(
child: Text('No Messages, Create New one'),
);
}
return ReorderableListView(
children: List.generate(
snapshot.data.length,
(index) {
return ListTile(
key: Key('$index'),
title: Text(
snapshot.data[index].title,
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 20,
),
),
subtitle: Text(snapshot.data[index].note,
maxLines: 4),
trailing: InkWell(
child: Icon(Icons.check,
color: Colors.green),
onTap: () {
TextEditingController txt =
TextEditingController();
txt.text = snapshot.data[index].note;
print(txt);
Route route = MaterialPageRoute(
builder: (context) =>
MyHomePage(custMessage: txt));
Navigator.push(context, route);
// addNewMessageDialog(txt);
},
),
isThreeLine: true,
onTap: () {
Route route = MaterialPageRoute(
builder: (context) => AddNote(
note: snapshot.data[index],
));
Navigator.push(context, route);
},
);
},
).toList(),
onReorder: (int oldIndex, int newIndex) {
setState(() {
if (newIndex > oldIndex) {
newIndex -= 1;
}
final item = snapshot.data.removeAt(oldIndex);
snapshot.data.insert(newIndex, item);
});
}
//Divider(color: Theme.of(context).accentColor),
);
}
}))
],
)),
floatingActionButton: _buildFAB(context, key: _fabKey),
);
}```