Get variable data from a Stateful widget in another Stateful widget and they have no relation to one another (They are not children nor parents to each other)
I want to be able to access an array (posts) that is located in another file... You can see the comments in the code for more information
I have this stateful widget
import 'package:flutter/material.dart';
import 'package:saviortv/modules/fetchPosts.dart';
import 'package:saviortv/ui/BuildPost.dart';
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
#override
Widget build(BuildContext context) {
return ListView.builder(
itemCount: posts == null ? 0 : posts.length, // <== here posts is undefined because it doesn't exist as I want to get it from the other file (See below)
itemBuilder: (BuildContext context, int index) {
return buildPost(context, posts, index); //Building the posts list view
},
);
}
}
The other Stateful widget
class FetchPosts extends StatefulWidget {
FetchPosts({Key key, this.pageNumber = 1}) : super(key: key);
final int pageNumber;
#override
_FetchPostsState createState() => _FetchPostsState(pageNumber);
}
class _FetchPostsState extends State<FetchPosts> {
_FetchPostsState(this.pageNumber);
int pageNumber;
List<wp.Post> posts = []; //<== I want this to be useable in the other file;
Future<String> getPosts() async {
var res = await fetchPosts(pageNumber);
print(pageNumber);
setState(() {
posts = res;
});
return "Success!";
}
// Get _ when app loads;
#override
void initState() {
super.initState();
this.getPosts();
}
#override
Widget build(BuildContext context) {
return Container();
}
}
How can I achieve that?
Related
I define a model reactively with GetX and send this model reactively to the view with the help of StateMixin. But this variable I sent changes the main variable as well. How exactly does this happen and how can I fix it? In the example I gave below, when I change the id value, the id automatically changes in the rawMyModel model. But I don't want it to change.
detail_controller.dart
class DetailController extends GetxController with StateMixin<Rx<MyModel>> {
late final MyModel rawMyModel;
#override
void onInit() async {
super.onInit();
rawMyModel = (Get.arguments as MyModel);
change(Rx(rawMyModel), status: RxStatus.success());
}
void reset() {
change(Rx(rawMyModel), status: RxStatus.success());
}
}
detail_page.dart
class DetailPage extends GetView<DetailController> {
const DetailPage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: controller.obx((Rx<MyModel>? myModel) => _buildBody(myModel: myModel!)),
);
}
Widget _buildBody({required Rx<MyModel> myModel}) {
print(myModel.value.toString());
myModel.update((val) => val.id = 5); // change
}
}
I'm starting to learn Flutter and I'm trying to write an application.
The application has a list of players in a ListView of SwitchListTile. This is working at the moment. I'm trying to add a function to delete one of the players from the lists.
class PlayersSwitchListTilesContainer extends StatelessWidget {
PlayersSwitchListTilesContainer({this.players});
final List<PlayerModel> players;
#override
Widget build(BuildContext context) {
return Scaffold(
body: ListView(
children : players.map<Widget>((PlayerModel p){
return PlayerSwtichListTile(singlePlayer: p);
}).toList()
),
);
}
}
class PlayerSwtichListTile extends StatefulWidget {
PlayerSwtichListTile({this.singlePlayer});
final PlayerModel singlePlayer;
void removePlayer()
{
// What goes here ???
print('Delete ' + singlePlayer.playerName);
}
#override
_PlayerSwtichListTileState createState() => new _PlayerSwtichListTileState(player: singlePlayer);
}
At the moment, when I try to delete a player it calls the correct code and prints the player's name. However, I'm struggling to see how to delete the player from the players list.
I'd be grateful for any pointers anyone has
From what I understand, to delete a player from the list of players you can do this but for this method, you need to provide the index number manually:
setState(() {
players.removeAt(index);
});
A better approach would be to use a listView.builder and add a button to the PlayerSwtichListTile which can receive the index from listView.builder so that whenever you click that button then that PlayerSwtichListTile player would get removed:
ListView.builder(
itemCount: players.length ?? 0,
itemBuilder: (context, index) {
return PlayerSwtichListTile(singlePlayer: p, index: index);}
)
class PlayerSwtichListTile extends StatefulWidget {
PlayerSwtichListTile({this.singlePlayer, this.index});
final int index;
final PlayerModel singlePlayer;
#override
_PlayerSwtichListTileState createState() => new _PlayerSwtichListTileState(player: singlePlayer);
}
class _PlayerSwtichListTile extends State<PlayerSwtichListTile > {
var player;
_PlayerSwtichListTile({this.player});
//call this function in ontap of that delete button
void removePlayer()
{
setState(() {
players.removeAt(widget.index);
});
}
#override
Widget build(BuildContext context) {
return Container();
}
}
How to change the widgets in a list item in flutter using bloc pacakage.
Should i use BlockBuilder or listener on the whole ListView.builder or only the individual items.
It would be nice if u share an example or tutorial.
eg If i have a checkbox i need to change its state on clicking it.
These are my Bloc classes
Bloc
const String SERVER_FAILURE_MESSAGE = 'Server Failure';
const String CACHE_FAILURE_MESSAGE = 'Cache Failure';
class MarkAttendanceBloc extends Bloc<MarkAttendanceEvent, MarkAttendanceState> {
final MarkStudentPresent markStudentPresent;
final MarkStudentAbsent markStudentAbsent;
MarkAttendanceBloc({#required this.markStudentPresent,#required this.markStudentAbsent});
#override
MarkAttendanceState get initialState => MarkedInitial();
#override
Stream<MarkAttendanceState> mapEventToState(MarkAttendanceEvent event) async* {
yield MarkedLoading();
if(event is MarkAbsentEvent){
final remotelyReceived = await markStudentAbsent(MarkStudentParams(classId: event.classId, courseId: event.courseId,studentId: event.studentId));
yield* _eitherLoadedOrErrorState(remotelyReceived);
}
else if(event is MarkPresentEvent){
final remotelyReceived = await markStudentPresent(MarkStudentParams(classId: event.classId, courseId: event.courseId,studentId: event.studentId));
yield* _eitherLoadedOrErrorState(remotelyReceived);
}
}
Stream<MarkAttendanceState> _eitherLoadedOrErrorState(
Either<StudentDetailsFacultyFailure,int> failureOrClasses,
) async* {
yield failureOrClasses.fold(
(failure) => MarkedError(_mapFailureToMessage(failure)),
(studentId) => Marked(studentId),
);
}
String _mapFailureToMessage(StudentDetailsFacultyFailure failure) {
switch (failure.runtimeType) {
case ServerError:
return SERVER_FAILURE_MESSAGE;
default:
return 'No internet';
}
}
}
State
abstract class MarkAttendanceState extends Equatable{
const MarkAttendanceState();
}
class MarkedInitial extends MarkAttendanceState{
const MarkedInitial();
#override
List<Object> get props => [];
}
class MarkedLoading extends MarkAttendanceState{
const MarkedLoading();
#override
List<Object> get props => [];
}
class Marked extends MarkAttendanceState{
final int studentId;
Marked(this.studentId);
#override
List<Object> get props => [studentId];
}
class MarkedError extends MarkAttendanceState{
final String errorMessage;
MarkedError(this.errorMessage);
#override
List<Object> get props => [errorMessage];
}
Event
import 'package:equatable/equatable.dart';
abstract class MarkAttendanceEvent extends Equatable {
const MarkAttendanceEvent();
}
class MarkPresentEvent extends MarkAttendanceEvent {
final int studentId;
final int courseId;
final int classId;
MarkPresentEvent(this.studentId, this.courseId, this.classId);
#override
List<Object> get props =>[studentId,courseId,classId];
}
class MarkAbsentEvent extends MarkAttendanceEvent {
final int studentId;
final int courseId;
final int classId;
MarkAbsentEvent(this.studentId, this.courseId, this.classId);
#override
List<Object> get props =>[studentId,courseId,classId];
}
Maybe by now you have found a solution but this is how i managed to achieve the same functionality using flutter cubits.
This code is hand written and not tested but it should guide you to achieve your goal
1 Declare the class objects
class ClassItem{
int? price;
bool isChecked;
ClassItem({
this.price,
this.isChecked=false,
});
}
class ClassOverall{
List<ClassItem> items;
double? total;
ClassOverall(this.items,this.total);
}
Declare the cubit class
class OverallCubit extends Cubit<ClassOverall> {
OverallCubit(ClassOverallinitialState) : super(initialState);
void checkUncheckCart(int index) {
if (!state.items
.elementAt(index).isChecked) {
state.items
.elementAt(index).isChecked =
!state.items
.elementAt(index).isChecked;
var t_total = double.tryParse(state.items
.elementAt(index).price!)! * 1;
emit(OverallCubit (state.items,state.total));
} else {
state.items.elementAt(index).isChecked =
!state.items
.elementAt(index).isChecked;
emit(OverallCubit (state.items,state.total));
}
calculateTotal();
}
void calculateTotal() {
var tot = 0.0;
for (var tick in state.items) {
if (tick.isChecked) {
tot = (tick.t_total! + tot);
}
}
emit(OverallCubit (state.items,tot));
}
}
Declare the top class widget to hold the state
class TopState extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BlocProvider(
create: (_) => OverallCubit(ClassOverall(items,0)),//fetch items from your source
child: Home(),
);
}
}
Declare the stateful widget and add a bloc builder
class Home extends StatefulWidget {
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<Home> {
#override
Widget build(BuildContext context) {
return BlocBuilder<OverallCubit, ClassOverall>(
builder: (ctx, state) {
return Column(children:[
ListView.builder(
padding: EdgeInsets.all(0.0),
shrinkWrap: true,
itemCount: state.items.length,
itemBuilder: (context, index) {
return ListTile(
onTap: () {
ctx
.read<OverallCubit>()
.checkUncheckCart(index);
},
tileColor: state.elementAt(index).isChecked ? Colors.red : Colors.white
title: Text(state.items.elementAt(index).price!),
);
}),
Text(state.total.toString),
]);
});
}
}
I'm trying to access the information I've passed over from a previous class before the build method begins. But it's saying only static members can be accessed in initializers. I don't really want to use the static property, partially because I wouldn't know how to use it, but also because I think it seems unnecessary. In previous pages I've been able to access the data but only after the build method, does anyone know how I can access it before? Thanks all
class FirstPage extends StatefulWidget {
#override
_FirstPageState createState() => _FirstPageState();
}
class _FirstPageState extends State<FirstPage> {
List<MyProvider> myList;
#override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
itemCount: myList.length,
itemBuilder: (context, index) {
String imgPath = myList[index].image;
String myTextPath = myList[index].name;
String locationNamePath = myList[index].location;
double distancePath = myList[index].distance;
String myName = '${myTextPath} ''${locationNamePath}';
return MyCard(
locationText: locationNamePath,
myText: myTextPath,
assetImage: Image.network(imgPath),
function: (){
Provider.of<Data>(context, listen: false).addLogo(Image.network(imgPath));
Navigator.push(context, MaterialPageRoute(builder: (context) => SecondPage(myName: myName,)));
},
);
}),
);
}
}
My next page accesses the data using a key but it seems not to be able to use it before the build method, and that's what I need to get around!
class SecondPage extends StatefulWidget {
final String myName;
const SecondPage({Key key, this.myName})
: super(key: key);
#override
_SecondPageState createState() => _SecondPageState();
}
class _SecondPageState extends State<SecondPage> with TickerProviderStateMixin {
final CollectionReference myItemsReference = Firestore.instance.collection('${widget.myName}');
// This is where the error is
#override
Widget build(BuildContext context) {
return Scaffold();
}
}
Use the initState method for anything related to initialization of State. See this for more on initState.
Example:
CollectionReference myItemsReference;
#override
void initState() {
myItemsReference = Firestore.instance.collection('${widget.myName}');
}
I have 2 screens in my Flutter app: a list of records and a screen for creating and editing records.
If I pass an object to the second screen that means I am going to edit this and if I pass null it means that I am creating a new item. The editing screen is a Stateful widget and I am not sure how to use this approach https://flutter.io/cookbook/navigation/passing-data/ for my case.
class RecordPage extends StatefulWidget {
final Record recordObject;
RecordPage({Key key, #required this.recordObject}) : super(key: key);
#override
_RecordPageState createState() => new _RecordPageState();
}
class _RecordPageState extends State<RecordPage> {
#override
Widget build(BuildContext context) {
//.....
}
}
How can I access recordObject inside _RecordPageState?
To use recordObject in _RecordPageState, you have to just write widget.objectname like below
class _RecordPageState extends State<RecordPage> {
#override
Widget build(BuildContext context) {
.....
widget.recordObject
.....
}
}
Full Example
You don't need to pass parameters to State using it's constructor.
You can easily access these using widget.myField.
class MyRecord extends StatefulWidget {
final String recordName;
const MyRecord(this.recordName);
#override
MyRecordState createState() => MyRecordState();
}
class MyRecordState extends State<MyRecord> {
#override
Widget build(BuildContext context) {
return Text(widget.recordName); // Here you direct access using widget
}
}
Pass your data when you Navigate screen :
Navigator.of(context).push(MaterialPageRoute(builder: (context) => MyRecord("WonderWorld")));
class RecordPage extends StatefulWidget {
final Record recordObject;
RecordPage({Key key, #required this.recordObject}) : super(key: key);
#override
_RecordPageState createState() => new _RecordPageState(recordObject);
}
class _RecordPageState extends State<RecordPage> {
Record recordObject
_RecordPageState(this. recordObject); //constructor
#override
Widget build(BuildContext context) {. //closure has access
//.....
}
}
example as below:
class nhaphangle extends StatefulWidget {
final String username;
final List<String> dshangle;// = ["1","2"];
const nhaphangle({ Key key, #required this.username,#required this.dshangle }) : super(key: key);
#override
_nhaphangleState createState() => _nhaphangleState();
}
class _nhaphangleState extends State<nhaphangle> {
TextEditingController mspController = TextEditingController();
TextEditingController soluongController = TextEditingController();
final scrollDirection = Axis.vertical;
DateTime Ngaysx = DateTime.now();
ScrollController _scrollController = new ScrollController();
ApiService _apiService;
List<String> titles = [];
#override
void initState() {
super.initState();
_apiService = ApiService();
titles = widget.dshangle; //here var is call and set to
}
I have to Navigate back to any one of the screens in the list pages but when I did that my onTap function stops working and navigation stops.
class MyBar extends StatefulWidget {
MyBar({this.pageNumber});
final pageNumber;
static const String id = 'mybar_screen';
#override
_MyBarState createState() => _MyBarState();
}
class _MyBarState extends State<MyBar> {
final List pages = [
NotificationScreen(),
AppointmentScreen(),
RequestBloodScreen(),
ProfileScreen(),
];
#override
Widget build(BuildContext context) {
var _selectedItemIndex = widget.pageNumber;
return Scaffold(
bottomNavigationBar: BottomNavigationBar(
elevation: 0,
backgroundColor: Colors.white,
unselectedItemColor: Colors.grey.shade700,
selectedItemColor: Color(kAppColor),
selectedIconTheme: IconThemeData(color: Color(kAppColor)),
currentIndex: _selectedItemIndex,
type: BottomNavigationBarType.fixed,
onTap: (int index) {
setState(() {
_selectedItemIndex = index;
});
},
You should use a Pub/Sub mechanism.
I prefer to use Rx in many situations and languages. For Dart/Flutter this is the package: https://pub.dev/packages/rxdart
For example, you can use a BehaviorSubject to emit data from widget A, pass the stream to widget B which listens for changes and applies them inside the setState.
Widget A:
// initialize subject and put it into the Widget B
BehaviorSubject<LiveOutput> subject = BehaviorSubject();
late WidgetB widgetB = WidgetB(deviceOutput: subject);
// when you have to emit new data
subject.add(deviceOutput);
Widget B:
// add stream at class level
class WidgetB extends StatefulWidget {
final ValueStream<LiveOutput> deviceOutput;
const WidgetB({Key? key, required this.deviceOutput}) : super(key: key);
#override
State<WidgetB> createState() => _WidgetBState();
}
// listen for changes
#override
void initState() {
super.initState();
widget.deviceOutput.listen((event) {
print("new live output");
setState(() {
// do whatever you want
});
});
}
In my app, often instead of using stateful widgets, I use mainly ChangeNotifierProvider<T> in main.dart, some model class
class FooModel extends ChangeNotifier {
var _foo = false;
void changeFooState() {
_foo = true;
notifyListeners();
}
bool getFoo () => _foo;
}
and
var foo = context.read<FooModel>();
# or
var foo = context.watch<FooModel>();
in my stateless widgets. IMO this gives me more precise control over the rebuilding upon runtime state change, compared to stateful widgets.
The recipe can be found in the official docs, the concept is called "lifting state up".