如何使用按钮将项目添加到动态列表中，或添加到具有列表的另一个屏幕

Question

我对flutter和编码还不太熟悉。我也是新来的，所以我为我在发布quesiton时可能犯的任何错误道歉。此外，如果需要的话，我使用android工作室
为了更具描述性，我想使用sharedPreferences将从第一屏幕的4个文本字段中获取的数据保存为数组，并将它们添加到第二屏幕的列表中。一个还没有任何内容的列表，如果保存了第一个屏幕中的数据，则该列表将显示包含已保存数据的1个项目
这是我混乱的代码：

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/services.dart';
import 'package:provider/provider.dart';
class ListProvider extends ChangeNotifier {
List<String> litems = List<String>();
List<String> get Items =>
this.litems;
set logList(List<String> value) {
litems = value;
notifyListeners();
}
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> with ChangeNotifier {
TextEditingController firstname = TextEditingController();
TextEditingController lastname = TextEditingController();
TextEditingController birthday = TextEditingController();
TextEditingController address = TextEditingController();
//

String data = "";
String data1 = "";
String data2 = "";
String data3 = "";
String firstname1 = "f";
String lastname1 = "l";
String birthday1 = "";
String address1 = "";

Future<bool>saveData() async{
SharedPreferences preferences = await SharedPreferences.getInstance();
return await preferences.setString(firstname1, firstname.text);
}
Future<bool>saveData1() async{
SharedPreferences preferences1 = await SharedPreferences.getInstance();
return await preferences1.setString(lastname1, lastname.text);
}
Future<bool>saveData2() async{
SharedPreferences preferences = await SharedPreferences.getInstance();
return await preferences.setString(birthday1, birthday.text);
}
Future<bool>saveData3() async{
SharedPreferences preferences1 = await SharedPreferences.getInstance();
return await preferences1.setString(address1, address.text);
}
///////////
Future<String> loadData() async{
SharedPreferences preferences = await SharedPreferences.getInstance();
return preferences.getString(firstname1);
}
Future<String> loadData1() async{
SharedPreferences preferences2 = await SharedPreferences.getInstance();
return preferences2.getString(lastname1);
}
Future<String> loadData2() async{
SharedPreferences preferences = await SharedPreferences.getInstance();
return preferences.getString(birthday1);
}
Future<String> loadData3() async{
SharedPreferences preferences2 = await SharedPreferences.getInstance();
return preferences2.getString(address1);
}

setData(){
loadData().then((value){
setState(() {
data = value;
});
});
}
setData1(){
loadData1().then((value){
setState(() {
data1 = value;
});
});
}
setData2(){
loadData2().then((value){
setState(() {
data2 = value;
});
});
}
setData3(){
loadData3().then((value){
setState(() {
data3 = value;
});
});
}
add(screen2){
screen2.litems.add(data);
notifyListeners();
setState(() {
});
}


@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
TextField(
controller: firstname,
decoration: InputDecoration(
hintText: "FIRST NAME"
),
),
TextField(
controller: lastname,
decoration: InputDecoration(
hintText: "LAST NAME"
),
),
TextField(
controller: birthday,
decoration: InputDecoration(
hintText: "BIRTHDAY"
),
),
TextField(
controller: address,
decoration: InputDecoration(
hintText: "ADDRESS"
),
),
RaisedButton(
onPressed: (){
saveData();
saveData1();
saveData2();
saveData3();
setData();
setData1();
setData2();
setData3();
add(screen2());
},
child: Text("ADD"),
),
RaisedButton(
onPressed: (){
Navigator.push(
context,
MaterialPageRoute(builder: (context) => screen2()),
);
},
child: Text("SHOW ALL"),
),
],
),
),
);
}
}

---

这是我需要访问列表的第二个屏幕。代码片段取自此

class screen2 extends StatefulWidget {
@override
State createState() => new DyanmicList();
}
class DyanmicList extends State<screen2> with ChangeNotifier {
List<String> litems = [];


final TextEditingController eCtrl = new TextEditingController();
@override
Widget build (BuildContext ctxt) {
return new Scaffold(
appBar: new AppBar(title: new Text("Screen2"),),
body: new Column(
children: <Widget>[
new TextField(
controller: eCtrl,
onSubmitted: (text) {
litems.add(text);
eCtrl.clear();
setState(() {});
},
),
new Expanded(
child: new ListView.builder
(
itemCount: litems.length,
itemBuilder: (BuildContext ctxt, int Index) {
return new Text(litems[Index]);
}
)
)
],
)
);
}
}

Answer 1

在屏幕1中，当按下提交按钮时，将4个信息添加到列表中并存储到sharedPreferences。

屏幕1

var list = List<Info>();
...
list.add(Info(firstName,lastName,birthday,address));
prefs.storeList(json.encode(list));

信息

class Info {
String firstName;
String lastName;
String birthday;
String address;
Info(this.firstName, this.lastName,this.birthday,this.address);
}

共享首选项

Future storeList(String info) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setString(INFO, info);
}

Future getListFromSharedPreferences() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
return prefs.getString(INFO);
}

屏幕2

在屏幕2小部件构建中，使用FutureBuilder从sharedPreferences获取列表。

FutureBuilder(
future: sharedPreferences.getListFromSharedPreferences(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return ListView.builder(
itemCount: (jsonDecode(snapshot.data)).length,
itemBuilder: (BuildContext ctxt, int index) {
return new Text(jsonDecode(snapshot.data)[index]);
});
} else {
return Text("No data");
}
});

Answer 2

如果您想使用SharedPreferences保存String的List，可以使用setStringList()而不是setString()。您可以通过以下方式实现这一点。

在您的第一个屏幕上，

RaisedButton(
onPressed: (){
List<String> _userData = [];
_userData.add(firstname.text);
_userData.add(lastname.text);
_userData.add(birthday.text);
_userData.add(address.text);

SharedPreferences myPrefs = await SharedPreferences.getInstance();
myPrefs.setStringList("user", _userData);
},
child: Text("ADD"),

然后在第二屏幕

class screen2 extends StatefulWidget {
@override
State createState() => new DyanmicList();
}
class DyanmicList extends State<screen2> {
List<String> litems = [];

@override
void initState() {
super.initState();
getUser();
}
getUser() async{
SharedPreferences myPrefs = await SharedPreferences.getInstance();
var userData=  myPrefs.getStringList("user");
setState((){
litems = userData;
});
}
final TextEditingController eCtrl = new TextEditingController();
@override
Widget build (BuildContext ctxt) {
return new Scaffold(
appBar: new AppBar(title: new Text("Screen2"),),
body: new Column(
children: <Widget>[
new TextField(
controller: eCtrl,
onSubmitted: (text) {
litems.add(text);
eCtrl.clear();
setState(() {});
},
),
new Expanded(
child: new ListView.builder
(
itemCount: litems.length,
itemBuilder: (BuildContext ctxt, int Index) {
return new Text(litems[Index]);
}
)
)
],
)
);
}
}