我有一个CheckBox项目选择屏幕（在浮动按钮中触发Navigator.push时打开）以检查我喜欢的项目，并且我希望这些项目在使用Navigator.pop时显示在屏幕上（当点击浮动按钮时）返回到其原始屏幕。但是我无法做到这一点，我认为list.map将在这里使用，但是我能够正确实现它。任何帮助都非常感谢。
您可以检查整个代码here。
我遇到问题的代码：
// CheckBox Item Selection Screen!
class FavoriteList extends StatefulWidget {
@override
_FavoriteListState createState() => _FavoriteListState();
}
class _FavoriteListState extends State<FavoriteList> {
final Set _saved = Set();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Add to Favorites!'), centerTitle: true, backgroundColor: Colors.red),
// backgroundColor: Colors.indigo,
body: SafeArea(
child: ListView.builder(
itemCount: 53,
itemBuilder: (context, index) {
return CheckboxListTile(
activeColor: Colors.red,
checkColor: Colors.white,
value: _saved.contains(index),
onChanged: (val) {
setState(() {
if(val == true){
_saved.add(index);
} else{
_saved.remove(index);
}
});
},
title: Row(
children: <Widget>[
Image.asset('lib/images/${images[index]}'),
SizedBox(width: 10,),
Text(nameOfSite[index]),
],
),
);
},
),
),
floatingActionButton: FloatingActionButton(foregroundColor: Colors.red,
child: Icon(Icons.check),
onPressed: (){
Navigator.pop(context, _saved); // Navigator.pop
},
),
);
}
}
这里是原始屏幕，我想return到_saved列表（我使用Set来避免重复）
class SecondPage extends StatefulWidget {
@override
_SecondPageState createState() => _SecondPageState();
}
class _SecondPageState extends State<SecondPage> {
@override
Widget build(BuildContext context) {
return
// if the `_saved` list contains something return the "_saved" list from
the CheckBox item selection screen, if not then
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Add Your Favorite Sites Here!❤',
style: TextStyle(color: Colors.white),
),
Container(
child: Icon(Icons.favorite, size: 150, color: Colors.blue[100]),
),
SizedBox(height: 250),
FloatingActionButton(
onPressed: () {
Navigator.push( //Navigator.push is here!
context,
MaterialPageRoute(
builder: (context) => FavoriteList(),
),
);
},
child: Icon(Icons.add),
foregroundColor: Colors.blue,
),
],
);
}
}
答案 0 :(得分：1)
答案 1 :(得分：0)
问题是当您弹出时，上一页的状态未更新。因此，弹出时返回带有选定项目（从复选框）的结果作为将来。弹出后，检查是否有任何结果，然后以新状态重建ui。
答案 2 :(得分：0)
您可以利用push的返回值
// _SecondPageState
FloatingActionButton(
onPressed: () async {
Set saved = await Navigator.push<Set>(
context,
MaterialPageRoute(builder: (context) => FavoriteList()),
);
setState(() {
// do something
});
},
),
答案 3 :(得分：0)
Navigator.push()具有返回值，您可以在调用Navigator.pop(时传递想要的内容
这是您应注意的主要代码：
SecondPage 类中的
：FloatingActionButton(
onPressed: () async {
final Set indices = await Navigator.push(
context,
MaterialPageRoute(
builder: (context) => FavoriteList(indices: _indices), // you may wanna passing in what you have checked.
),
);
if (indices != null) {
// do what you want, like setState()
setState(() {
final List tempIndices = _indices;
tempIndices.addAll(indices);
_indices = tempIndices.toSet().toList();
});
}
},
),
和 FavoriteList 类中的
floatingActionButton: FloatingActionButton(
onPressed: () {
Navigator.pop(context, _saved);
},
),
如果要检查完整的代码：
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Navigator Data',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: SecondPage(),
);
}
}
class SecondPage extends StatefulWidget {
@override
_SecondPageState createState() => _SecondPageState();
}
class _SecondPageState extends State<SecondPage> {
List _indices = [];
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
padding: const EdgeInsets.symmetric(horizontal: 25.0, vertical: 75.0),
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Text(
'Add Your Favorite Sites Here!',
style: TextStyle(
color: Colors.black,
fontSize: 24.0,
),
),
Expanded(
child: ListView.builder(
itemCount: _indices.length,
itemBuilder: (context, index) {
return Center(
child: Text(
'${_indices[index]}',
style: TextStyle(
color: Colors.red,
fontSize: 24.0,
),
),
);
},
),
),
FloatingActionButton(
onPressed: () async {
final Set indices = await Navigator.push(
context,
MaterialPageRoute(
builder: (context) => FavoriteList(indices: _indices),
),
);
if (indices != null) {
setState(() {
final List tempIndices = _indices;
tempIndices.addAll(indices);
_indices = tempIndices.toSet().toList();
});
}
},
child: Icon(
Icons.add,
color: Colors.white,
),
foregroundColor: Colors.blue,
),
],
),
),
);
}
}
class FavoriteList extends StatefulWidget {
FavoriteList({
Key key,
this.indices,
}) : super(key: key);
final List indices;
@override
_FavoriteListState createState() => _FavoriteListState();
}
class _FavoriteListState extends State<FavoriteList> {
final Set _saved = Set();
@override
void initState() {
super.initState();
_saved.addAll(widget.indices);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Add to Favorites!'),
centerTitle: true,
backgroundColor: Colors.red,
),
body: SafeArea(
child: ListView.builder(
itemCount: 53,
itemBuilder: (context, index) {
return CheckboxListTile(
activeColor: Colors.red,
checkColor: Colors.white,
value: _saved.contains(index),
onChanged: (val) {
setState(() {
if (val == true) {
_saved.add(index);
} else {
_saved.remove(index);
}
});
},
title: Row(
children: <Widget>[
Text('$index'),
],
),
);
},
),
),
floatingActionButton: FloatingActionButton(
foregroundColor: Colors.red,
child: Icon(Icons.check),
onPressed: () {
Navigator.pop(context, _saved);
},
),
);
}
}