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();
}
Related
I need to expose a couple of functions of a Stateful Widget. Since these functions depend on the state of the widget, I created a variable to store the state.
However, I am getting a compile time warning:
This class (or a class that this class inherits from) is marked as '#immutable', but one or more of its instance fields aren't final.
My Code:
class ItemWidget extends StatefulWidget {
final Record record;
final Function additem;
final Function removeItem;
var state;
ItemWidget(this.record, this.additem, this.removeItem);
#override
_ItemWidgetState createState() {
return this.state = new _ItemWidgetState();
}
// These are public functions which I need to expose.
bool isValid() => state.validate();
void validate() => state.validate();
}
Is there a better way /correct way of achieving this?
Thanks.
You should write the function on state, and access it via GlobalKey.
import 'package:flutter/material.dart';
class ItemWidget extends StatefulWidget {
final Record record;
final Function additem;
final Function removeItem;
const ItemWidget(
Key? key,
this.record,
this.additem,
this.removeItem,
) : super(key: key);
#override
ItemWidgetState createState() => ItemWidgetState();
}
class ItemWidgetState extends State<ItemWidget> {
bool isValid() {
return true;
}
void validate() {}
#override
Widget build(BuildContext context) {
// TODO: implement build
throw UnimplementedError();
}
}
https://api.flutter.dev/flutter/widgets/GlobalKey-class.html
I have this model class which has a refresh method,
class Model{
...
void refresh(){}
}
I'm calling this method from Parent widget like this,
class Parent extends StatefulWidget {
#override
_Parent State createState() => _Parent State();
}
class _Parent State extends State<Parent >
with SingleTickerProviderStateMixin {
final Model model = Model();
#override
Widget build(BuildContext context) {
return Column(
children:[
Child(model: model),
IconButton(onPressed:model.refresh)
]
);
}
}
this is child widget,
class Child extends StatefulWidget {
final Model model;
const Child({
Key? key,
required this.model,
}) : super(key: key);
#override
_ChildState createState() => _ChildState();
}
class _ChildState extends State<Child>
with SingleTickerProviderStateMixin {}
so what I want is to override that method in here and call that whenever it's called from parent.
In short what I need is a callback from parent to child which need to be inside the Model class. So How can I do this?
ok so I knew I can do it with state management but using another library was not a option and I totally forgot about the change notifier so I implemented like this,
class Model extends ChangeNotifier{
void refresh(){
notifyListeners();
}
}
class Child extends StatefulWidget{
final Model model
Child(this.model);
...
#override
initState(){
model.addListener((){});
}
}
class Parent extends StatelessWidget{
final Model model = Model();
...
Child(model),
SomeWidget(
onTap:(){
model.refresh();
}
),
}
I have a code that is responsible for the data filter: the user make the criteria that are important to him and clicks "Apply". And sees a list based on the selected filters. But then these filters are reset, and if the user wants to make filters based on the previous ones, he has to select everything again. How to make that the state of the filters is saved and the user can continue filtering based on the previous request?
dialog_filter.dart
class FilterDialog extends StatefulWidget {
final void Function(Map<String, List<String>?>) onApplyFilters;
const FilterDialog({Key? key, required this.onApplyFilters}) : super(key: key);
#override
State<FilterDialog> createState() => _FilterDialogState();
}
class _FilterDialogState extends State<FilterDialog> {
Map<String, List<String>?> filters = {};
void _handleCheckFilter(bool checked, String key, String value) {
final currentFilters = filters[key] ?? [];
if(checked) {
currentFilters.add(value);
} else {
currentFilters.remove(value);
}
filters[key] = currentFilters;
}
page_main.dart
class MainPage extends StatefulWidget {
const MainPage({Key? key}) : super(key: key);
#override
State<MainPage> createState() => _MainPageState();
}
class _MainPageState extends State<MainPage> {
List<Phone> filteredPhones = phoneList;
void _filter(Map<String, List<String>?> filters) {
setState(() {
filteredPhones = phoneList;
filters.forEach((key, value) {
if((value ?? []).isNotEmpty) {
filteredPhones = filteredPhones.where((phone) {
switch(key) {}
}).toList();
}
});
});
}
class Filter {
String name;
bool Function(Phone) filterFn;
Filter({required this.name, required this.filterFn});
}
you need to use state management libraries like provider, bloc, mobx , riverpod etc.
So if you still want use stateful widget then you have to maintain a list of selected filters at parent level pass to your dialog and return back when user selects anything. This will be very complex and bug prone to do with only stateful widget.
If don't want use any libraries then you can use ValueNotifier or InheritedWidget. But I would suggest state management library is more easier. Start with provider it's easiest.
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;
}
I'm still a beginner with streams and bloc pattern.
I would like to do following:
Trigger an event.
Based on the event get back a state with an object
Store this object as JSON in a database.
All examples are showing, how an object can be displayed in a widget with BlocBuilder. But I don't need to display the value, only get it and store it. I can't figure out how to get the value into a variable.
How can I do that? In the View class I'm dispatching the event, but now I need to know how to get the object in the state back without using BlocBuilder.
Here are the details:
Bloc
class SchoolBloc extends Bloc<SchoolEvent, SchoolState> {
final SchoolRepository _schoolRepository;
StreamSubscription _schoolSubscription;
SchoolBloc({#required SchoolRepository schoolRepository})
: assert(schoolRepository != null),
_schoolRepository = schoolRepository;
#override
SchoolState get initialState => SchoolsLoading();
#override
Stream<SchoolState> mapEventToState(SchoolEvent event) async* {
if (event is LoadSchool) {
yield* _mapLoadSchoolToState();
Stream<SchoolState> _mapLoadSchoolToState(LoadSchool event) async* {
_schoolSubscription?.cancel();
_schoolSubscription = _schoolRepository.school(event.id).listen(
(school) {
SchoolLoaded(school);
}
);
}
Event
#immutable
abstract class SchoolEvent extends Equatable {
SchoolEvent([List props = const []]) : super(props);
}
class LoadSchool extends SchoolEvent {
final String id;
LoadSchool(this.id) : super([id]);
#override
String toString() => 'LoadSchool';
}
State
#immutable
abstract class SchoolState extends Equatable {
SchoolState([List props = const []]) : super(props);
}
class SchoolLoaded extends SchoolState {
final School school;
SchoolLoaded([this.school]) : super([school]);
#override
String toString() => 'SchoolLoaded { school: $school}';
}
View
class CourseView extends StatefulWidget {
#override
State<StatefulWidget> createState() => _CourseViewState();
}
class _CourseViewState extends State<CourseView> {
#override
initState() {
super.initState();
print("this is my init text");
final _schoolBloc = BlocProvider.of<SchoolBloc>(context);
_schoolBloc.dispatch(LoadSchool("3kRHuyk20UggHwm4wrUI"));
// Here I want to get back the school object and save it to a db
}
Test that fails
For testing purposes I have done following:
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:teach_mob/core/blocs/school/school.dart';
class CourseView extends StatefulWidget {
#override
State<StatefulWidget> createState() => _CourseViewState();
}
class _CourseViewState extends State<CourseView> {
#override
void initState() {
super.initState();
BlocProvider.of<SchoolBloc>(context)
.dispatch(LoadSchool("3kRHuyk20UggHwm4wrUI"));
}
#override
Widget build(BuildContext context) {
return BlocListener<SchoolBloc, SchoolState>(
listener: (context, state) {
print("BlocListener is triggered");
},
child: Text("This is a test")
);
}
}
The LoadSchool event is triggered. The text in the child attribute of BlocListener is displayed, but the listener function that should print "BlocListener is triggered" is not executed.
Use BlocListener. It is meant to be used for those cases you mention.