Flutter:参数中传递的值第一次在第二页为null

Question

Flutter：参数中传递的值第一次在第二页为null。如果我进行热重新加载，则该值不为空。

也许是因为TabBar，但在使用TabBar时，第一次如何获得真正的价值？

请帮我找到问题的解决方案

第一页。这里的idBou不为空

class BoutiquePage extends StatefulWidget {
int idboutique;
BoutiquePage({this.idboutique});
@override
_BoutiquePageState createState() => _BoutiquePageState();
}
class _BoutiquePageState extends State<BoutiquePage> {
SharedPreferences sharedPreferences;


final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
String idBou ;
String nomAbon ;
String prenomAbon ;
String telAbon ;
String addAbon;
String nomBou;
String ville;
String pays;
String lien_photo_bout;

bool _isLoading = false;

String _errorText;
get article_afficher333 => article_afficher333;
@override
void initState() { 
setState((){ 
getShaerInstance();
}); 
super.initState();
}
getShaerInstance() async {
sharedPreferences = await SharedPreferences.getInstance(); 
}

Future<Map<String, dynamic>> getAllStoreInfoData2(int idboutique) async {
final response = await http.get(http://xxxxxx.com+"boutique/home?id_bout="+idboutique.toString()); 
if (response.statusCode == 200) {
final jsonResponse = json.decode(response.body);
BoutiqueData myData = new BoutiqueData.fromJson(jsonResponse);

Map<String, dynamic> boutiqueinfodata = Map();
boutiqueinfodata["boutiqueType"] = myData.v_boutique.typeBoutique; 
return boutiqueinfodata;
} else {
throw Exception("Failed to load Data");
}
}

//SharedPreferences
@override
Widget build(BuildContext context) {
Widget myboutiqueinfodata = FutureBuilder(
future: getAllStoreInfoData2(widget.idboutique),
builder: (context, snapshot) {
if (snapshot.hasData) {
Map<String, dynamic> alldata = snapshot.data;          
typeBoutique = alldata["boutiqueType"];        
List<ListeInfoBoutique> boutiqueInfoData = alldata["boutiqueInfoData"];   

for (var i = 0; i < boutiqueInfoData.length; i++) {
idBou = boutiqueInfoData[i].idBou;
nomAbon = boutiqueInfoData[i].nomAbon;
prenomAbon = boutiqueInfoData[i].prenomAbon;
telAbon = boutiqueInfoData[i].telAbon;
addAbon = boutiqueInfoData[i].addAbon; 
}
return   Scaffold(
body: ListView(
children: <Widget>[

],
),
);

}else if (snapshot.hasError) {
return Container(
child: Center(
child: Text(AppLocalizations.of(context)
.translate('_MSG_ER_CONNEXION_CHARGE_DATA'), 
style: TextStyle(
fontSize: 18,
fontFamily: 'Questrial'
),),
),
);
}
return new Center(
child: CircularProgressIndicator(),
);
});
return DefaultTabController(
length: 5,
child: Scaffold(
key: _scaffoldKey,
appBar: AppBar(
title: Text(AppLocalizations.of(context)
.translate('_MY_STORE'), style: TextStyle(color: Colors.white, fontFamily: "Questrial"),),
iconTheme: new IconThemeData(color: Color(0xFFFFFFFF)),
actions: <Widget>[
//
],
bottom: TabBar(
isScrollable: true,
indicatorColor: Colors.white,
indicatorWeight: 5.0,
//onTap: (){},
tabs: <Widget>[
Tab(
child: Container(
child: Text(AppLocalizations.of(context)
.translate('_STORE_INFO'), style: TextStyle(color: Colors.white, fontSize: 18.0, fontFamily: 'Questrial'),),
),
),
Tab(
child: Container(
child: Text(AppLocalizations.of(context)
.translate('_MY_ARTICLES'), style: TextStyle(color: Colors.white, fontSize: 18.0, fontFamily: 'Questrial'),),
),
),
],
),
),
body: TabBarView(
children: <Widget>[
myboutiqueinfodata, 
MesArticles(idboutique: idBou),
],
),
),
);
}
}

第二页，第一次打印为空并且在热重新加载后变为非空

class MesArticles extends StatefulWidget {
final String idboutique;
const MesArticles({Key key, this.idboutique}) : super(key: key);
@override
_MesArticleState createState() => _MesArticleState();
}
class _MesArticleState extends State<MesArticles> {
@override
Widget build(BuildContext context) {
print(widget.idboutique.toString()); // it print null for fist time. After hot reload it become not null
return Scaffold(
body: Text(widget.idboutique.toString()), //<== it print null for fist time.
);
}
}

Answer 1

试试这个代码。我认为Future builder是它抛出null的原因。

class BoutiquePage extends StatefulWidget {
int idboutique;
BoutiquePage({this.idboutique});
@override
_BoutiquePageState createState() => _BoutiquePageState();
}
class _BoutiquePageState extends State<BoutiquePage> {
SharedPreferences sharedPreferences;


final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
String idBou ;
String nomAbon ;
String prenomAbon ;
String telAbon ;
String addAbon;
String nomBou;
String ville;
String pays;
String lien_photo_bout;

bool _isLoading = false;
bool _isLoaded = false;
bool _isError = false;

String _errorText;
get article_afficher333 => article_afficher333;
@override
void initState() { 
setState((){ 
getShaerInstance();
}); 
super.initState();
}
getShaerInstance() async {
sharedPreferences = await SharedPreferences.getInstance(); 
}

Future<Map<String, dynamic>> getAllStoreInfoData2(int idboutique) async {
final response = await http.get("http://xxxxxx.com/" + "boutique/home?id_bout="+idboutique.toString()); 
if (response.statusCode == 200) {
final jsonResponse = json.decode(response.body);
BoutiqueData myData = new BoutiqueData.fromJson(jsonResponse);

Map<String, dynamic> boutiqueinfodata = Map();
boutiqueinfodata["boutiqueType"] = myData.v_boutique.typeBoutique; 
return boutiqueinfodata;
} else {
throw Exception("Failed to load Data");
}
}

//SharedPreferences
initDataFromServer(idboutique) async {
try {

var alldata = await  getAllStoreInfoData2(idboutique);         
var typeBoutique = alldata["boutiqueType"];        
List<ListeInfoBoutique> boutiqueInfoData = alldata["boutiqueInfoData"];   

for (var i = 0; i < boutiqueInfoData.length; i++) {
idBou = boutiqueInfoData[i].idBou;
nomAbon = boutiqueInfoData[i].nomAbon;
prenomAbon = boutiqueInfoData[i].prenomAbon;
telAbon = boutiqueInfoData[i].telAbon;
addAbon = boutiqueInfoData[i].addAbon; 
}
setState(() {
_isLoaded = true;
_isLoading = false;
_isError = false;
});
} catch (e) {
print(e);
setState(() {
_isLoaded = true;
_isLoading = true;
_isError = true;
});
}

}
@override
Widget build(BuildContext context) {
if (_isLoaded == false && _isLoading == false) {
_isLoading = true;
initDataFromServer(widget.idboutique);
}
return DefaultTabController(
length: 5,
child: Scaffold(
key: _scaffoldKey,
appBar: AppBar(
title: Text(AppLocalizations.of(context)
.translate('_MY_STORE'), style: TextStyle(color: Colors.white, fontFamily: "Questrial"),),
iconTheme: new IconThemeData(color: Color(0xFFFFFFFF)),
actions: <Widget>[
//
],
bottom: TabBar(
isScrollable: true,
indicatorColor: Colors.white,
indicatorWeight: 5.0,
//onTap: (){},
tabs: <Widget>[
Tab(
child: Container(
child: Text(AppLocalizations.of(context)
.translate('_STORE_INFO'), style: TextStyle(color: Colors.white, fontSize: 18.0, fontFamily: 'Questrial'),),
),
),
Tab(
child: Container(
child: Text(AppLocalizations.of(context)
.translate('_MY_ARTICLES'), style: TextStyle(color: Colors.white, fontSize: 18.0, fontFamily: 'Questrial'),),
),
),
],
),
),
body: TabBarView(
children: <Widget>[
_isLoaded == false ? Center(
child: CircularProgressIndicator(),
): (_isError == false ? Text("Your data Loaded") : Text("Error")),

_isLoaded == false ? Center(
child: CircularProgressIndicator(),
): (_isError == false ? MesArticles(idboutique: idboutique) : Text("Error")), 

],
),
),
);
}
}

class MesArticles extends StatefulWidget {
final String idboutique;
const MesArticles({Key key, this.idboutique}) : super(key: key);
@override
_MesArticleState createState() => _MesArticleState(idboutique: idboutique);
}
class _MesArticleState extends State<MesArticles> {
final String idboutique;
_MesArticleState({this.idboutique});
@override
Widget build(BuildContext context) {
print(widget.idboutique.toString()); // it print null for fist time. After hot reload it become not null
return Scaffold(
body: Text(widget.idboutique.toString()),
);
}
}