为什么initState()被调用两次? [英] Why is initState() called twice?
本文介绍了为什么initState()被调用两次?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
initState()被调用了两次.
initState() is called twice on the first Widget I route to.
我删除了所有方法调用，并在initState()方法中完成了工作，以排除它以某种方式自行调用的可能性.它所做的只是调用super.initState().
I have removed all method calls and work being done in the initState() method to exclude any possibility that it somehow calls itself. All it does is calling super.initState().
routes.dart:
routes.dart:
final routes = {
'/login' : (BuildContext context) => new LoginPage(),
'/' : (BuildContext context) => new LoginPage()
};
main.dart:
main.dart:
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Personnel Ledger',
initialRoute: '/login',
routes: routes,
theme: ThemeData(
scaffoldBackgroundColor: Color(0xFF30778B)
),
);
}
}
LoginPage.dart:
LoginPage.dart:
class LoginPage extends StatefulWidget {
@override
LoginPageState createState() => LoginPageState();
}
class LoginPageState extends State<LoginPage> {
TextEditingController emailTextfieldCtrl;
TextEditingController passwordTextfieldCtrl;
AuthHttpService authHttpService;
bool loggaInDisabled;
Widget invalidCredentialsText;
@override
void initState() {
super.initState();
// setInvalidCredentialsTextVisibleWithoutSetState(false);
// authHttpService = new AuthHttpService();
// emailTextfieldCtrl = new TextEditingController();
// passwordTextfieldCtrl = new TextEditingController();
loggaInDisabled = true;
// refreshApplicationAccessToken();
}
@override
Widget build(BuildContext context) {
return Scaffold(
resizeToAvoidBottomPadding: false,
body: SafeArea(
child: Stack(
children: <Widget>[
Container(
decoration: BoxDecoration(
gradient: LinearGradient(
begin: Alignment.topLeft,
end: Alignment.bottomRight,
colors: [Color(0xFF30778B), Color(0xFF2F3648)])),
child: Center(
child: Stack(
children: <Widget>[
Column(
children: <Widget>[
Spacer(
flex: 11,
),
Flexible(
flex: 50,
child: Container(
child: Image.asset("assets/knowe-logo.png"),
),
),
],
),
Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Spacer(
flex: 35,
),
Flexible(
flex: 10,
child: Container(
child: Row(
children: <Widget>[
Spacer(
flex: 1,
),
Flexible(
flex: 7,
child: Theme(
data:
ThemeData(hintColor: Color(0xFF9E9C9C)),
child: TextField(
style:
TextStyle(color: Color(0xFF9E9C9C)),
cursorColor: Color(0xFF9E9C9C),
controller: emailTextfieldCtrl,
onChanged: emailTextfieldChanged,
decoration: InputDecoration(
prefixIcon: Icon(
Icons.person,
size: 30,
color: Color(0xFF9E9C9C),
),
labelText: "Email",
border: new UnderlineInputBorder(
borderSide: BorderSide(
color: Color(0xFF9E9C9C),
style: BorderStyle.solid,
width: 2))),
),
),
),
Spacer(
flex: 1,
)
],
),
),
),
Flexible(
flex: 10,
child: Container(
margin: EdgeInsets.only(top: 5),
child: Row(
children: <Widget>[
Spacer(
flex: 1,
),
Flexible(
flex: 7,
child: Theme(
data:
ThemeData(hintColor: Color(0xFF9E9C9C)),
child: TextField(
obscureText: true,
style:
TextStyle(color: Color(0xFF9E9C9C)),
cursorColor: Color(0xFF9E9C9C),
controller: passwordTextfieldCtrl,
onChanged: passwordTextfieldChanged,
decoration: InputDecoration(
prefixIcon: Icon(
Icons.lock,
size: 26,
color: Color(0xFF9E9C9C),
),
labelText: "Lösenord",
border: new UnderlineInputBorder(
borderSide: BorderSide(
color: Color(0xFF9E9C9C),
style: BorderStyle.solid,
width: 2))),
),
),
),
Spacer(flex: 1)
],
),
),
),
Flexible(
flex: 10,
child: Container(
child: invalidCredentialsText,
)),
Flexible(
flex: 20,
child: Container(
margin: EdgeInsets.only(top: 0),
child: Row(
children: <Widget>[
Spacer(
flex: 1,
),
Expanded(
flex: 7,
child: Container(
height: 50,
child: RaisedButton(
disabledColor: Color(0xff395A52),
child: Text(
"Logga in",
style: TextStyle(
color: loggaInDisabled
? Color(0xff7a7a7a)
: Colors.white),
),
onPressed: loggaInDisabled
? null
: loggaInPressed,
color: Color(0xff10846D),
),
),
),
Spacer(flex: 1)
],
),
),
),
Container(
margin: EdgeInsets.only(top: 7.5),
child: InkWell(
child: Text(
"Glömt lösenord?",
style: TextStyle(color: Color(0xFF9E9C9C)),
),
onTap: glomtLosenordPressed,
),
),
Spacer(
flex: 10,
),
],
)
],
),
),
),
Column(
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Expanded(
child: Column(
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Container(
alignment: Alignment.bottomLeft,
padding: EdgeInsets.only(left: 15, bottom: 10),
color: Colors.transparent,
child: InkWell(
onTap: privacyPolicyTapped,
child: Text("Privacy policy",
style: TextStyle(
color: Color(0xFF9E9C9C),
fontSize: 15,
decoration: TextDecoration.underline)),
),
)
],
),
)
],
)
],
),
),
);
}
setInvalidCredentialsTextVisible(bool show) {
setState(() {
if (show)
invalidCredentialsText = Row(
children: <Widget>[
Spacer(flex: 1),
Flexible(
flex: 7,
child: Column(
children: <Widget>[
Flexible(
flex: 4,
child: Container(
alignment: Alignment.centerLeft,
child: Row(
children: <Widget>[
Flexible(
flex: 1,
child: Icon(
Icons.error,
size: 20,
color: Color(0xFF9E9C9C),
),
),
Flexible(
flex: 5,
child: Container(
padding: EdgeInsets.only(left: 2.5),
child: Text(
"Invalid email or password",
style: TextStyle(color: Color(0xFF9E9C9C)),
),
),
)
],
),
),
),
Spacer(
flex: 2,
)
],
),
),
Spacer(flex: 1)
],
);
else
invalidCredentialsText = Row(
children: <Widget>[
Spacer(flex: 1),
Flexible(
flex: 7,
child: Column(
children: <Widget>[
Flexible(
flex: 3,
child: Container(
alignment: Alignment.centerLeft,
child: Row(
children: <Widget>[
Flexible(
flex: 1,
child: Icon(
Icons.error,
size: 20,
color: Color(0x009E9C9C),
),
),
Flexible(
flex: 5,
child: Container(
padding: EdgeInsets.only(left: 2.5),
child: Text(
"",
style: TextStyle(color: Color(0xFF9E9C9C)),
),
),
)
],
),
),
),
Spacer(
flex: 2,
)
],
),
),
Spacer(flex: 1)
],
);
});
}
setInvalidCredentialsTextVisibleWithoutSetState(bool show) {
if (show)
invalidCredentialsText = Row(
children: <Widget>[
Spacer(flex: 1),
Flexible(
flex: 7,
child: Column(
children: <Widget>[
Flexible(
flex: 4,
child: Container(
alignment: Alignment.centerLeft,
child: Row(
children: <Widget>[
Flexible(
flex: 1,
child: Icon(
Icons.error,
size: 20,
color: Color(0xFF9E9C9C),
),
),
Flexible(
flex: 5,
child: Container(
padding: EdgeInsets.only(left: 2.5),
child: Text(
"Invalid email or password",
style: TextStyle(color: Color(0xFF9E9C9C)),
),
),
)
],
),
),
),
Spacer(
flex: 2,
)
],
),
),
Spacer(flex: 1)
],
);
else
invalidCredentialsText = Row(
children: <Widget>[
Spacer(flex: 1),
Flexible(
flex: 7,
child: Column(
children: <Widget>[
Flexible(
flex: 3,
child: Container(
alignment: Alignment.centerLeft,
child: Row(
children: <Widget>[
Flexible(
flex: 1,
child: Icon(
Icons.error,
size: 20,
color: Color(0x009E9C9C),
),
),
Flexible(
flex: 5,
child: Container(
padding: EdgeInsets.only(left: 2.5),
child: Text(
"",
style: TextStyle(color: Color(0xFF9E9C9C)),
),
),
)
],
),
),
),
Spacer(
flex: 2,
)
],
),
),
Spacer(flex: 1)
],
);
}
privacyPolicyTapped() {
launch("https://www.knowe.se/policy.html");
}
emailTextfieldChanged(String newEmail) {
setState(() {
loggaInDisabled = shouldDisableLoggaIn();
});
}
passwordTextfieldChanged(String newPassword) {
setState(() {
loggaInDisabled = shouldDisableLoggaIn();
});
}
bool shouldDisableLoggaIn() {
var email = emailTextfieldCtrl.text;
var password = passwordTextfieldCtrl.text;
return !(email != null &&
email != "" &&
password != null &&
password != "");
}
loggaInPressed() {
logIn();
}
logIn() {
var email = emailTextfieldCtrl.text;
var password = passwordTextfieldCtrl.text;
var appId = "4d45d54d45d45dd45d45d54d54d54d54";
var response = authHttpService.logIn(email, password, appId);
onLoading();
response
.then((response) async {
Navigator.pop(context);
if (response.statusCode == 200) {
setInvalidCredentialsTextVisible(false);
var tokensModel = TokensModel.fromJson(json.decode(response.body));
final prefs = await SharedPreferences.getInstance();
prefs.setString("RefreshToken", tokensModel.refreshToken);
prefs.setString(
"ApplicationAccessToken", tokensModel.appAccessToken);
navigateToMainMenuPage();
} else
setInvalidCredentialsTextVisible(true);
})
.timeout(Duration(seconds: 10))
.catchError((error) {
Navigator.pop(context);
showMessageDialog(
"Fel vid inloggning", "Kunde inte få kontakt med servern.");
});
}
configureFCM() {
// var fcmHelper = new FCMHelper();
// fcmHelper.configureFCM(context);
// fcmHelper.registerFCMToken(userModel);
}
glomtLosenordPressed() {
navigateToResetPasswordPage();
}
refreshApplicationAccessToken() async {
var prefs = await SharedPreferences.getInstance();
var refreshToken = prefs.getString("RefreshToken");
if (refreshToken != null && refreshToken != "") {
var response =
authHttpService.refreshApplicationAccessToken(refreshToken);
onLoading();
response
.then((response) async {
Navigator.pop(context);
if (response.statusCode == 200) {
var tokensModel =
TokensModel.fromJson(json.decode(response.body));
var applicationAccessToken = tokensModel.appAccessToken;
var prefs = await SharedPreferences.getInstance();
prefs.setString("ApplicationAccessToken", applicationAccessToken);
navigateToMainMenuPage();
} else
showMessageDialog("Inloggningssessionen utgången",
"Logga in igen med dina uppgifter.");
})
.timeout(Duration(seconds: 10))
.catchError((error) {
Navigator.pop(context);
showMessageDialog(
"Fel vid inloggning", "Kunde inte få kontakt med servern.");
});
}
}
navigateToMainMenuPage() {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => MainMenuPage()),
);
}
navigateToResetPasswordPage() {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => ResetPasswordPage()),
);
}
void onLoading() {
showDialog(
context: context,
barrierDismissible: false,
builder: (_) => Scaffold(
backgroundColor: Color.fromRGBO(0, 0, 0, 0.25),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Container(
width: 40,
height: 40,
child: CircularProgressIndicator(strokeWidth: 5)),
Container(
margin: EdgeInsets.only(top: 15),
child: Text(
"Loggar in...",
style: TextStyle(color: Colors.white, fontSize: 20),
),
)
],
),
)),
);
}
void showMessageDialog(String title, String body) {
try {
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: new Text(title),
content: new Text(body),
);
});
} catch (e) {
print(e.toString());
}
}
}
实际结果: LoginPage中的initState()方法被调用两次.
Actual result: initState() method in LoginPage is called twice.
预期结果和目标: initState()仅应调用一次.
Expected result and goal: initState() should only be called once.
推荐答案
这是两个事实的组合:
- 每条路线都是完全独立的.
/不与/login共享状态，因此从/到/login将触发/login上LoginPage上的initState. -
initialRoute: '/login'并不意味着该应用程序直接在/login上启动 .
- each route is entirely independent.
/do not share state with/login, therefore going from/to/loginwill trigger aninitStateon theLoginPagefrom/login. initialRoute: '/login'does not mean that the app starts directly on/login.
将initialRoute参数设置为/foo/bar，该应用将以以下路线历史记录开头:
With the initialRoute argument to /foo/bar, the app will start with the following route history:
-
/ -
/foo -
/foo/bar
//foo/foo/bar
这样，即使您具有initialRoute属性，也仍会推送/.
As such, even though you have an initialRoute property, / is still pushed.
这篇关于为什么initState()被调用两次?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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