I have a app with a List<Match> as state, which is kept in
class MatchesChangeNotifier extends ChangeNotifier {
List<Match> matches;
refresh() async {
matches = await MatchesFirestore.fetchMatches(); // goes to db
notifyListeners();
}
}
then I have the following widgets (simplified)
class AvailableMatches extends StatelessWidget {
#override
Widget build(BuildContext context) {
var matches = context.watch<MatchesChangeNotifier>().matches;
return Column(children: matches.map(e => MatchInfo(e)).toList());
}
}
class MatchInfo extends StatelessWidget {
Match match;
MatchInfo(this.match);
Widget build(BuildContext context) {
// use match for a bunch of stuff
return InkWell(
child: ...,
onTap: () async {
await Navigator.push(context,
MaterialPageRoute(builder: (context) => MatchDetails(match)));
await context.read<MatchesChangeNotifier>().refresh();
}
}
In MatchDetails I have a bunch of buttons. One of them has this callback
onTap() async => await context.read<MatchesChangeNotifier>().refresh()
When I tap this button I see (debugging) that
AvailableMatches gets rebuilt (since it watches matches)
MatchInfo gets rebuilt (since it's down the tree w.r.t. AvailableMatches)
MatchDetails doesn't get re-built
Why is that? Is it because it is somehow called in the onTap function?
After I press the button I would like to see MatchDetails change when it's on top of the screen (i.e. the user is seeing it). Instead this doesn't happen
If I modify the way I push MatchDetails from MatchInfo with this ugly trick the thing works but I would like to avoid it
await Navigator.push(context,
MaterialPageRoute(builder: (context) =>
MatchDetails(context.watch<MatchesChangeNotifier>().matches.firstWhere((m) => m.id == match.id))));
Related
I am getting this error when I have signed out from my flutter app and trying to log in again:
StateError (Bad state: Stream has already been listened to.)
The code that gives me this error is on my first page:
#override
void initState() {
AwesomeNotifications().actionStream.listen((notification) async {
if (notification.channelKey == 'scheduled_channel') {
var payload = notification.payload['payload'];
var value = await FirebaseFirestore.instance
.collection(widget.user.uid)
.doc(payload)
.get();
navigatorKey.currentState.push(PageRouteBuilder(
pageBuilder: (_, __, ___) => DetailPage(
user: widget.user,
i: 0,
docname: payload,
color: value.data()['color'].toString(),
createdDate: int.parse((value.data()['date'].toString())),
documentId: value.data()['documentId'].toString(),)));
}
});
super.initState();
}
And on another page that contains the sign out code.
await FirebaseAuth.instance.signOut();
if (!mounted) return;
Navigator.pushNamedAndRemoveUntil(context,
"/login", (Route<dynamic> route) => false);
What can I do to solve this? Is it possible to stop listen to actionstream when I log out? Or should I do it in another way?
Streams over all are single use, they replace the callback hell that that ui is, at first a single use streams can seem useless but that may be for a lack of foresight. Over all (at lest for me) flutter provides all the necessary widgets to not get messy with streams, you can find them in the Implementers section of ChangeNotifier and all of those implement others like TextEditingController.
With that, an ideal (again, at least for me) is to treat widgets as clusters where streams just tie them in a use case, for example, the widget StreamBuilder is designed to build on demand so it only needs something that pumps changes to make a "live object" like in a clock, a periodic function adds a new value to the stream and the widget just needs to listen and update.
To fix your problem you can make .actionStream fit the case you are using it or change a bit how are you using it (having a monkey patch is not good but you decide if it is worth it).
This example is not exactly a "this is what is wrong, fix it", it is more to showcase a use of how pushNamedAndRemoveUntil and StreamSubscription can get implemented. I also used a InheritedWidget just because is so useful in this cases. One thing you should check a bit more is that the variable count does not stop incrementing when route_a is not in focus, the stream is independent and it will be alive as long as the widget is, which in your case, rebuilding the listening widget is the error.
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(App());
const String route_a = '/route_a';
const String route_b = '/route_b';
const String route_c = '/route_c';
class App extends StatelessWidget {
Stream<int> gen_nums() async* {
while (true) {
await Future.delayed(Duration(seconds: 1));
yield 1;
}
}
#override
Widget build(BuildContext ctx) {
return ReachableData(
child: MaterialApp(
initialRoute: route_a,
routes: <String, WidgetBuilder>{
route_a: (_) => Something(stream: gen_nums()),
route_b: (_) => FillerRoute(),
route_c: (_) => SetMount(),
},
),
);
}
}
class ReachableData extends InheritedWidget {
final data = ReachableDataState();
ReachableData({super.key, required super.child});
static ReachableData of(BuildContext ctx) {
final result = ctx.dependOnInheritedWidgetOfExactType<ReachableData>();
assert(result != null, 'Context error');
return result!;
}
#override
bool updateShouldNotify(ReachableData old) => false;
}
class ReachableDataState {
String? mount;
}
// route a
class Something extends StatefulWidget {
// If this widget needs to be disposed then use the other
// constructor and this call in the routes:
// Something(subscription: gen_nums().listen(null)),
// final StreamSubscription<int> subscription;
// Something({required this.subscription, super.key});
final Stream<int> stream;
Something({required this.stream, super.key});
#override
State<Something> createState() => _Something();
}
class _Something extends State<Something> {
int count = 0;
void increment_by(int i) => setState(
() => count += i,
);
#override
void initState() {
super.initState();
widget.stream.listen(increment_by);
// To avoid any funny errors you should set the subscription
// on pause or the callback to null on dispose
// widget.subscription.onData(increment_by);
}
#override
Widget build(BuildContext ctx) {
var mount = ReachableData.of(ctx).data.mount ?? 'No mount';
return Scaffold(
body: InkWell(
child: Text('[$count] Push Other / $mount'),
onTap: () {
ReachableData.of(ctx).data.mount = null;
Navigator.of(ctx).pushNamed(route_b);
},
),
);
}
}
// route b
class FillerRoute extends StatelessWidget {
const FillerRoute({super.key});
#override
Widget build(BuildContext ctx) {
return Scaffold(
body: InkWell(
child: Text('Go next'),
// Option 1: go to the next route
// onTap: () => Navigator.of(ctx).pushNamed(route_c),
// Option 2: go to the next route and extend the pop
onTap: () => Navigator.of(ctx)
.pushNamedAndRemoveUntil(route_c, ModalRoute.withName(route_a)),
),
);
}
}
// route c
class SetMount extends StatelessWidget {
const SetMount({super.key});
#override
Widget build(BuildContext ctx) {
return Scaffold(
body: InkWell(
child: Text('Set Mount'),
onTap: () {
ReachableData.of(ctx).data.mount = 'Mounted';
// Option 1: pop untill reaches the correct route
// Navigator.of(ctx).popUntil(ModalRoute.withName(route_a));
// Option 2: a regular pop
Navigator.of(ctx).pop();
},
),
);
}
}
I am trying to use flutter provider in order to carry my state down a widget sub-tree/route, and while it works for the direct child of the widget that provided the change notifier class, it does not for the next one in line.
As far as I understand, the change notifier class should be passed down. To be more specific, I am trying to access it through context.read() in a function being called in its initState function.
Am I doing something wrong?
The code below illustrates my code.
Where it class notifier is provided:
onTap: () {
// Select body area
context.read<Patient>().selectBodyArea(areas[index]);
// Open complaint list
FlowRepresentation flow = context.read<Patient>().getFlow();
Navigator.push(
context,
MaterialPageRoute(builder: (context) =>
ChangeNotifierProvider.value(
value: flow,
child: const ChiefComplaintList()
)
)
);
}
Navigation to the problem widget in ChiefComplaintList:
onTap: () {
// Select complaint
context.read<FlowRepresentation>().selectComplaint(ccs[index]);
// Show factors
Navigator.push(
context,
MaterialPageRoute(builder: (context) => const AttenuationFactors())
);
}
Where I'm having trouble accessing the change notifier class:
void getData() async {
_nrFactors = await context.read<FlowRepresentation>().getAttenuationFactors();
setState(() {}); // rebuild widget with data
}
#override
void initState() {
super.initState();
print("Initiated Attenuation Factors Lists State");
getData();
}
Assume that I'm on page-A now. I navigate to page-B. When I pop the page-B and come back to page-A, currently nothing happens. How can I reload page-A and load the new API data from the init state of page-A? Any Ideas?
first main page
void refreshData() {
id++;
}
FutureOr onGoBack(dynamic value) {
refreshData();
setState(() {});
}
void navigateSecondPage() {
Route route = MaterialPageRoute(builder: (context) => SecondPage());
Navigator.push(context, route).then(onGoBack);
}
second page
RaisedButton(
onPressed: () {
Navigator.pop(context);
},
child: Text('Go Back'),
),
more details check here
From the explanation that you have described, so when you are popping the page.
This below Code will be on the second page.
Navigator.of(context).pop(true);
so the true parameter can be any thing which ever data that you want to send.
And then when you are pushing from one page to another this will be the code.
this is on the first page.
final result = await Navigator.push(
context,
MaterialPageRoute(builder: (context) => const PageOne()),
);
so if you print the result you will get the bool value that you send from the second page.
And based on bool you can hit the api. if the bool true make an api call.
Let me know if this works.
There are one more solutions for this situtation.
İf you want to trigger initState again
You can use pushAndRemoveUntil method for navigation. ( if you use only push method this is not remove previous page on the stack)
You can use key
You can set any state manegement pattern.( not for only trigger initState again)
There are 2 ways:
Using await
await Navigator.push(context, MaterialPageRoute(builder: (context){
return PageB();
}));
///
/// REFRESH DATA (or) MAKE API CALL HERE
Passing fetchData constructor to pageB and call it on dispose of pageB
class PageA {
void _fetchData() {}
Future<void> goToPageB(BuildContext context) async {
await Navigator.push(context, MaterialPageRoute(builder: (context) {
return PageB(onFetchData: _fetchData);
}));
}
}
class PageB extends StatefulWidget {
const PageB({Key? key, this.onFetchData}) : super(key: key);
final VoidCallback? onFetchData;
#override
State<PageB> createState() => _PageBState();
}
class _PageBState extends State<PageB> {
#override
void dispose() {
widget.onFetchData?.call();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Container();
}
}
I have an InkWell which uses onTap to perform some actions. When the button is tapped, I like an indicator to be shown (in case the action is long-running). However, the setState in the InkWell does not trigger its children to be re-rendered. The code is as follows:
class PrimaryButtonState extends State<PrimaryButton> {
bool _apiCall;
Widget getWidget() {
if(_apiCall) {
return new CircularProgressIndicator();
} else {
return Text(
widget.label,
);
}
}
#override
Widget build(BuildContext context) {
final List<Color> colors = //omitted
return InkWell(
child: Container(
decoration: // omitted
child: getWidget(), // not updated when _apiCall changes !!!!!
),
onTap: () {
setState(() {
_apiCall = true;
});
widget.onTab(context);
setState(() {
_apiCall = false;
});
}
);
}
}
How can I solve this that getWidget returns the correct widget dependent on _apiCall?
EDIT:
The widget.onTap contains the following:
void performLogin(BuildContext context) {
final String userName = _userName.text.trim();
final String password = _password.text.trim();
UserService.get().loginUser(userName, password).then((val) {
Navigator.push(
context, MaterialPageRoute(builder: (context) => MainLayout()));
}).catchError((e) {
// omitted
});
}
it is passed with the widget:
class PrimaryButton extends StatefulWidget {
final bool isPrimary;
final String label;
final Function(BuildContext context) onTab;
PrimaryButton(this.label, this.isPrimary, this.onTab);
#override
State<StatefulWidget> createState() => PrimaryButtonState();
}
My main concern is, that the given onTap method should not know it is "bound" to a UI widget and therefore should not setState. Also, as this is a general button implementation I like it to be interchangeable (therefore, onTap is not hardcoded)
It looks like your problem is because you are calling setState() twice in your onTap() function. Since onTap() is not an async function it will set _apiCall = true in the first setState, then immediately run widget.onTab(context) and then immediately perform the second setState() to set _apiCall = false so you never see the loading widget.
To fix this you will need to make your onTab function an async function and await for a value in your onTap function for your InkWell:
onTap: () async {
setState(() {
_apiCall = true;
});
await widget.onTab(context);
setState(() {
_apiCall = false;
});
}
This will also let you use the results of your onTab function to show errors or other functionality if needed.
If you are unsure how to use async functions and futures here is a good guide on it that goes over this exact kind of use case.
I have a home page which when clicked takes me to another page through navigates, do some operations in then press the back button which takes me back to the home page. but the problem is the home page doesn't get refreshed.
Is there a way to reload the page when i press the back button and refreshes the home page?
You can trigger the API call when you navigate back to the first page like this pseudo-code
class PageOne extends StatefulWidget {
#override
_PageOneState createState() => new _PageOneState();
}
class _PageOneState extends State<PageOne> {
_getRequests()async{
}
#override
Widget build(BuildContext context) {
return new Scaffold(
body: new Center(
child: new RaisedButton(onPressed: ()=>
Navigator.of(context).push(new MaterialPageRoute(builder: (_)=>new PageTwo()),)
.then((val)=>val?_getRequests():null),
),
));
}
}
class PageTwo extends StatelessWidget {
#override
Widget build(BuildContext context) {
//somewhere
Navigator.pop(context,true);
}
}
Or you can just use a stream if the API is frequently updated, the new data will be automatically updated inside your ListView
For example with firebase we can do this
stream: FirebaseDatabase.instance.reference().child(
"profiles").onValue
And anytime you change something in the database (from edit profile page for example), it will reflect on your profile page. In this case, this is only possible because I am using onValue which will keep listening for any changes and do the update on your behalf.
(In your 1st page): Use this code to navigate to the 2nd page.
Navigator.pushNamed(context, '/page2').then((_) {
// This block runs when you have returned back to the 1st Page from 2nd.
setState(() {
// Call setState to refresh the page.
});
});
(In your 2nd page): Use this code to return back to the 1st page.
Navigator.pop(context);
use result when you navigate back from nextScreen as follow :
Navigator.of(context).pop('result');
or if you are using Getx
Get.back(result: 'hello');
and to reload previous page use this function :
void _navigateAndRefresh(BuildContext context) async {
final result = await Get.to(()=>NextScreen());//or use default navigation
if(result != null){
model.getEMR(''); // call your own function here to refresh screen
}
}
call this function instead of direct navigation to nextScreen
The solution which I found is simply navigating to the previous page:
In getx:
return WillPopScope(
onWillPop: () {
Get.off(() => const PreviousPage());
return Future.value(true);
},
child: YourChildWidget(),
or if you want to use simple navigation then:
Navigator.pushReplacement(context, MaterialPageRoute(builder: (context) =>PreviousPage() ,));
Simply i use this:
onPressed: () {
Navigator.pop(context,
MaterialPageRoute(builder: (context) => SecondPage()));
},
this to close current page:
Navigator.pop
to navigate previous page:
MaterialPageRoute(builder: (context) => SecondPage())
In FirtsPage, me adding this for refresh on startUpPage:
#override
void initState() {
//refresh the page here
super.initState();
}
For a more fine-grained, page-agnostic solution I came up with this Android Single LiveEvent mimicked behaviour.
I create such field inside Provider class, like:
SingleLiveEvent<int> currentYearConsumable = SingleLiveEvent<int>();
It has a public setter to set value. Public consume lets you read value only once if present (request UI refresh). Call consume where you need (like in build method).
You don't need Provider for it, you can use another solution to pass it.
Implementation:
/// Useful for page to page communication
/// Mimics Android SingleLiveEvent behaviour
/// https://stackoverflow.com/questions/51781176/is-singleliveevent-actually-part-of-the-android-architecture-components-library
class SingleLiveEvent<T> {
late T _value;
bool _consumed = true;
set(T val) {
_value = val;
_consumed = false;
}
T? consume() {
if (_consumed) {
return null;
} else {
_consumed = true;
return _value;
}
}
}
await the navigation and then call the api function.
await Navigator.of(context).pop();
await api call
You can do this with a simple callBack that is invoked when you pop the route. In the below code sample, it is called when you pop the route.
class HomePage extends StatefulWidget {
#override
_HomePageState createState() => new _HomePageState();
}
class _HomePageState extends State<HomePage> {
_someFunction()async{
Navigator.of(context).push(MaterialPageRoute(builder: (_)=> PageTwo(
onClose():(){
// Call setState here to rebuild this widget
// or some function to refresh data on this page.
}
)));
}
#override
Widget build(BuildContext context) {
return SomeWidget();
}
...
} // end of widget
class PageTwo extends StatelessWidget {
final VoidCallback? onClose;
PageTwo({Key? key, this.onClose}) : super(key: key);
#override
Widget build(BuildContext context) {
return SomeWidget(
onEvent():{
Navigate.of(context).pop();
onClose(); // call this wherever you are popping the route
);
}
}