I'm having trouble accessing the variable user on _MenuScreenState:
class MenuScreen extends StatefulWidget {
final User user;
MenuScreen(this.user);
#override
_MenuScreenState createState() => _MenuScreenState();
}
class _MenuScreenState extends State<MenuScreen> {
final User userInMenu = widget.user;
}
The problem displayed is "The instance member 'widget' can't be accessed in an initializer.
Try replacing the reference to the instance member with a different expression".
You have to do it inside initState like the following:
class MenuScreen extends StatefulWidget {
final User user;
MenuScreen(this.user);
#override
_MenuScreenState createState() => _MenuScreenState();
}
class _MenuScreenState extends State<MenuScreen> {
User userInMenu = widget.user;
#override
void initState() {
super.initState();
userInMenu = widget.user;
}
Related
I have a problem with classes. I keep the user data in user_info_screen with Google auth. How can I pull this user data in a class that has this data on another page?
class UserInfoScreen extends StatefulWidget {
UserInfoScreen({Key key, User user})
: _user = user,
super(key: key);
final User _user;
#override
_UserInfoScreenState createState() => _UserInfoScreenState();
}
class _UserInfoScreenState extends State<UserInfoScreen> {
User _user;
The page I want to use (user) by pulling this data
class HomeView extends StatefulWidget {
#override
_HomeViewState createState() => _HomeViewState();
}
class _HomeViewState extends State<HomeView> {
}
Thank you.
A good way to handle it, espacially if you will use the user data on other pages, is to implement a store concept : https://pub.dev/packages/get
UserInfoScreen.dart
GetStorage box = GetStorage();
box.write('userData', _user);
HomeView.dart
GetStorage box = GetStorage();
User _user = box.read('userData');
Or pass it as an argument
UserInfoScreen.dart
Get.to(() => HomeView(), arguments: [
{"userData": _user}
]);
HomeView.dart
dynamic argumentData = Get.arguments;
#override
void onInit() {
print(argumentData[0]['userData']);
super.onInit();
}
I have a simple code snippet:
class CreateNewViewPage extends StatefulWidget {
final ComponentConfiguration currentComponentConfiguration = ComponentConfiguration(1, 1);
final Components components = Components(currentComponentConfiguration);
#override
State<StatefulWidget> createState() => _CreateNewViewPage();
}
Unfortunately, when I want to send currentComponentConfiguration to the Components class construct, I get the following information: The instance member 'currentComponentConfiguration' can't be accessed in an initializer.
How can I fix this problem?
You can't use a non-static variable for initialzing another non-static variable. Either make currentComponentConfiguration a static member or do components object creation in State class (_CreateNewViewPageState).
Using Static
class CreateNewViewPage extends StatefulWidget {
static final ComponentConfiguration currentComponentConfiguration = ComponentConfiguration(1, 1);
final Components components = Components(currentComponentConfiguration);
#override
_CreateNewViewPageState createState() => _CreateNewViewPageState();
}
Using State class
class CreateNewViewPage extends StatefulWidget {
final ComponentConfiguration currentComponentConfiguration = ComponentConfiguration(1, 1);
#override
_CreateNewViewPageState createState() => _CreateNewViewPageState();
}
class _CreateNewViewPageState extends State<CreateNewViewPage> {
Components components;
#override
void initState() {
super.initState();
components = Components(widget.currentComponentConfiguration);
}
#override
Widget build(BuildContext context) {
return Text('Hello, World!', style: Theme.of(context).textTheme.headline4);
}
}
In my project, I pass data from one widget to another using this code:
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
TranslatorSignUpStep2(transModel: this._translatorModel),
),
);
Then I retrive it in the other widget by the code below:
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State();
}
The problem is, in the TranslatorSignUpStep2 class I want to assign the passed-in transModel to another variable so I write this code
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
TranslatorModel _translatorModel = widget.transModel;
}
But it seems like the widget can't be used outside the build method so I get error saying
The instance member 'widget' can't be accessed in an initializer.. Anyone know how to get over this ?
you can access widget in initState function like this.
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
TranslatorModel _translatorModel ;
#override
void initState() {
_translatorModel = widget.transModel;
}
}
Just add the keyword late while initializing:
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State();
}
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
late TranslatorModel _translatorModel = widget.transModel;
}
try this code :
TranslatorSignUpStep2 :
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State(this.transModel);
}
TranslatorSignUpStep2 class :
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
_TranslatorSignUpStep2State(TranslatorModel _tempModel ){
this._translatorModel =_tempModel;
};
TranslatorModel _translatorModel ;
}
Add static keyword when innitializing
class OrderDetails extends StatefulWidget {
int selectedDays;
OrderDetails({
this.range,)};
#override
_OrderDetailsState createState() => _OrderDetailsState();
}
class _OrderDetailsState extends State<OrderDetails> {
String getRange;
#override
void initState() {
super.initState();
getRange = widget.range;
}
I got a Visual Studio warning on my class (below) saying "This class (or a class which this class inherits from) is marked as '#immutable', but one or more of its instance fields are not final: UserSignIn._email", but I cannot mark this argument as final because I initialise it in the constructor
Without final :
class UserSignIn extends StatefulWidget {
TextEditingController _email;
UserSignIn({String emailInput}) {
this._email = TextEditingController(text: (emailInput ?? ""));
}
#override
_UserSignInState createState() => _UserSignInState();
}
class _UserSignInState extends State<UserSignIn> {
#override
Widget build(BuildContext context) {
...
}
}
How to do this ?
Thank you
You should put the TextEditingController in the state class and initialise it in the initState method, like this.
And keep in mind that the StatefulWidget can be different every time when the widget tree is changed, so don't put anything in there that is not immutable.
Keep everything dynamic in the State class
class UserSignIn extends StatefulWidget {
final String emailInput;
const UserSignIn({Key key, this.emailInput}) : super(key: key);
#override
_UserSignInState createState() => _UserSignInState();
}
class _UserSignInState extends State<UserSignIn> {
TextEditingController _controller;
#override
void initState() {
_controller = TextEditingController(text: widget.emailInput);
super.initState();
}
...
}
I am trying to call a function(addGeoPoint) from Map class in another function named onDragEnd of the class SwipeButton both of which is are stateful.
class Map extends StatefulWidget {
//Some Code
_MapState createState() => _MapState();
}
class _MapState extends State<Map> {
//Some Functions
void addGeoPoint() async{
}
File 2
class SwipeButton extends StatefulWidget {
// Some Code
#override
SwipeButtonState createState() => SwipeButtonState();
}
class SwipeButtonState extends State<SwipeButton>
with SingleTickerProviderStateMixin {
// Some functions
void _onDragEnd(DragEndDetails details) {
// I want to call the addGeoPoint() function here
}
}
To do so, I tried creating an instance of the class Map as Map mapScreen = new Map and then access the function using mapScreen.addGeoPoint() but, I achieved no success. Any help to solve this problem would be appreciated.
You can use VoidCallBacks to communicate between Widgets:
Map:
class Map extends StatefulWidget {
//Some Code
_MapState createState() => _MapState();
}
class _MapState extends State<Map> {
//Some Functions
void addGeoPoint() async{
//do things
}
Widget buildSwipeButton() {
...
...
return SwipeButton(
onAddGeoPoint: addGeoPoint,
);
}
SwipeButton:
class SwipeButton extends StatefulWidget {
final VoidCallback onAddGeopoint;
SwipeButton({this.onAddGeoPoint});
// Some Code
#override
SwipeButtonState createState() => SwipeButtonState();
}
class SwipeButtonState extends State<SwipeButton>
with SingleTickerProviderStateMixin {
// Some functions
void _onDragEnd(DragEndDetails details) {
// I want to call the addGeoPoint() function here
widget.onAddGeoPoint();
}
}
You can declare your widget like this
class YourWidget extends StatefulWidget {
final Function callback;
YourWidget({#required this.textButton});
#override
YourWidgetState createState() => YourWidgetState();
}
then you can pass de function like this in your stateful parent
YourWidget(
callback: (){}
)
ant then you can use in YourWidget like this in other widget or other function
widget.callback()