Develop Reference

How Can i get only this text? Without " DocumentReference<Map<String, dynamic>> "

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``
#override
Widget build(BuildContext context) {
return GestureDetector(
child: Scaffold(
appBar: AppBar(automaticallyImplyLeading: false),
backgroundColor: Colors.black,
body: StreamBuilder<DocumentSnapshot<Map<String, dynamic>>>(
stream: FirebaseFirestore.instance.collection('History').doc(userId).snapshots(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
final DocumentSnapshot<Map<String, dynamic>>? getDocument = snapshot.data;
final Map<String, dynamic>? map = getDocument?.data();
var setList = map!['userchat'];
return ListView.builder(
itemCount: setList.length,
itemBuilder: (context, index) {
final get = setList[index];
print(get);
return const Text('data');
},
);
}
return const Text('data');
},
),
),
);
}
``

For getting the required text, i.e., the text in index = 3, you can use a conditional check in itemBuilder.
if(index==3){
final get = setList[index];
print(get);
return const Text('data');
}else{
return const SizedBox.shrink();
}
SizedBox.shrink() helps in avoiding to return a null value, but in turn returns a widget which doesn't show up, or simply nothing.
You can use it if you want, or can go with Text('data').

Flutter - FutureBuilder sometimes gives me null distance on list of items

I get a list of items in home of my app.
In each one of this items I show the distance from the user and the item.
But in some item I have the distance and in others get null
This is my partial code:
class ProductHorizontalListItem extends StatelessWidget {
const ProductHorizontalListItem({
Key? key,
required this.product,
required this.coreTagKey,
this.onTap,
}) : super(key: key);
final Product product;
final Function? onTap;
final String coreTagKey;
#override
Widget build(BuildContext context) {
// print('***Tag*** $coreTagKey${PsConst.HERO_TAG__IMAGE}');
final PsValueHolder valueHolder =
Provider.of<PsValueHolder>(context, listen: false);
Future<double> getCurrentLocation() async {
Position position = await Geolocator.getCurrentPosition();
double lat = position.latitude;
double long = position.longitude;
final double distanceInMeters = Geolocator.distanceBetween(
double.parse(position.latitude.toString()),
double.parse(position.longitude.toString()),
double.parse(product.itemLocation!.lat.toString()),
double.parse(product.itemLocation!.lng.toString()),
);
return Future.value(distanceInMeters);
}
return FutureBuilder<double>(
future: getCurrentLocation(),
builder: (BuildContext context, AsyncSnapshot<double> snapshot) {
return InkWell(
onTap: onTap as void Function()?,
child: Container(
margin: const EdgeInsets.only(
left: PsDimens.space4, right: PsDimens.space4,
bottom: PsDimens.space12),
child: Text(
'${snapshot.data}',
textAlign: TextAlign.start,
style: Theme.of(context).textTheme.caption!.copyWith(
color: PsColors.textColor3
)))
);});
}
}
Somebody can tell me why?
Thank you.

In the FutureBuilder you need to handle the different statuses of the future. With your current code you are building the widget on the very first snapshot. The reason of the null values is likely this, in most of the cases (if not every time) the first snapshot will not contain valid value.
Look at the following code about how to handle the different cases in a FutureBuilder:
return FutureBuilder<double>(
future: getCurrentLocation(),
builder: (BuildContext context, AsyncSnapshot<double> snapshot) {
// the future is not completed yet, so show a progress indicator
if (snapshot.connectionState == ConnectionState.waiting) {
return CircularProgressIndicator();
}
// the future is completed, but with an error, you have to handle it
if (snapshot.hasError) {
return...;
}
// the future is completed without error, but still you need
// to check whether it contains data, this is basically a check
// against null
if (snapshot.hasData) {
return...;
}
// if your code arrives here, it means the future is already
// completed, there was no error but the data returned is null
return...;
});

Information from api doesn't show - Flutter

I have a problem with Future builder in Flutter. It gets the info from api successfully but doesn't show it. When I put print and print the info from api, it is ok and it shows the movies name without any problems. here is my code:
class Search extends StatefulWidget {
final String value;
Search({Key key, String this.value}) : super(key: key);
#override
_SearchState createState() => _SearchState();
}
class _SearchState extends State<Search> {
var title;
Future getSearch({index}) async {
http.Response response = await http.get(
'https://api.themoviedb.org/3/search/company?api_key=6d6f3a650f56fd6b3347428018a20a73&query=' +
widget.value);
var results = json.decode(response.body);
setState(() {
this.title = results['results'];
});
return title[index]['name'];
}
getName(index) {
return title[index]['name'];
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: Color(0xff1d1d27),
body: Column(
children: [
Expanded(
child: FutureBuilder(
initialData: [],
future: getSearch(),
builder: (context, snapshot) {
return ListView.builder(itemBuilder: (context, index) {
Padding(
padding:
EdgeInsets.symmetric(horizontal: 30, vertical: 20),
child: Container(
color: Colors.white,
child: Text(getName(index).toString()),
),
);
});
},
))
],
)),
);
}
}

Please Use this code, It works fine to fetch the names and show them on the list,
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
class Search extends StatefulWidget {
final String value;
Search({Key key, String this.value}) : super(key: key);
#override
_SearchState createState() => _SearchState();
}
class _SearchState extends State<Search> {
var title;
var results;
getSearch() async {
http.Response response = await http.get(
'https://api.themoviedb.org/3/search/company?api_key=6d6f3a650f56fd6b3347428018a20a73&query=' +
widget.value);
results = json.decode(
response.body); //make it global variable to fetch it everywhere we need
return results['results'][0]['name'];
}
getName(index) {
return results['results'][index]['name'];
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: Color(0xff1d1d27),
body: Column(
children: [
Expanded(
child: FutureBuilder(
// initialData: [],
future: getSearch(),
builder: (context, snapshot) {
String name =
snapshot.data; // to get the data from the getSearch
print(name);
if (snapshot.hasData) {
// if there is data then show the list
return ListView.builder(
itemCount: results['results']
?.length, // to get the list length of results
itemBuilder: (context, index) {
return Padding(
padding: EdgeInsets.symmetric(
horizontal: 30, vertical: 20),
child: Container(
color: Colors.white,
child: Text(getName(index)
.toString()), // pass the index in the getName to get the name
),
);
});
} else {
// if there is no data or data is not loaded then show the text loading...
return new Text("Loading...",
style: TextStyle(fontSize: 42, color: Colors.white));
}
},
))
],
)),
);
}
}
P.S
To Learn the basics of Futurebuilder You can see this article For more learning
I have commented the code to explain more to you.

Flutter : Provider do not update data in the previous screen

In my Flutter application I am using Provider version 4.0.4 to manage the state of my app. In basic terms, my app will list down the nearby companies with their rating. users can select a organisation, open it and add their rating as well, so the final rating will be updated. I am using the Consumer concept in Provider to handle the tasks.
In NearByPlacesPage class I am listing down the companies around me with rating information. User can click on a company and they will be taken to OrganizationPage page.
In OrganizationPage class, the rating is displayed again. user can add their rating to the system. Then the rating information in both OrganizationPage page and NearByPlacesPage (back page) need to be updated.
The issue is, when the user update the rating, the rating in OrganizationPage get updated but not NearByPlacesPage in back stack. When we go back to NearByPlacesPage, we can clearly see the old rating values. The page need to be reloaded to get updated values.
Below are the important sections in my code
NearByPlacesPage
class NearByPlacesPage extends StatelessWidget {
int orgTypeID;
String orgTypeName;
NearByPlacesPage(this.orgTypeID, this.orgTypeName);
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
body: MultiProvider(
providers: [
ChangeNotifierProvider(create: (context) => RatingService()),
],
child: SingleChildScrollView(
child: _NearByPlacesPageUI(orgTypeID, orgTypeName),
),
),
appBar: AppBar(
title: Text(orgTypeName),
),
);
}
}
class _NearByPlacesPageUI extends StatefulWidget {
int orgTypeID;
String orgTypename;
_NearByPlacesPageUI(this.orgTypeID, this.orgTypename);
#override
State<StatefulWidget> createState() {
return _NearByPlacesPageState();
}
}
class _NearByPlacesPageState extends State<_NearByPlacesPageUI> {
#override
Widget build(BuildContext context) {
Consumer<RatingService>(builder: (context, data, child){
return Flexible(
child: ListView.builder(
itemCount: orgList.length,
itemBuilder:(BuildContext context, int index) {
Organization organization = orgList[index];
if (organization.isDisabled != true) {
RatingValue ratingValue = data.getData();
return Container(
margin: EdgeInsets.only(
top: 5, left: 5, right: 5),
child: _buildPlace(organization, ratingValue));
} else {
return Container();
}
},),
);
},);
}
}
OrganizationPage
class OrganizationPage extends StatelessWidget {
Organization organization;
String orgTypeName;
OrganizationPage(this.organization, this.orgTypeName);
#override
Widget build(BuildContext context) {
return Scaffold(
body: SingleChildScrollView(
child: _OrganizationPageUI(organization, orgTypeName),
),
backgroundColor: Colors.white,
appBar: AppBar(
title: Text(organization.name),
),
);
}
}
class _OrganizationPageUI extends StatefulWidget {
Organization organization;
String orgTypeName;
_OrganizationPageUI(this.organization, this.orgTypeName);
#override
State<StatefulWidget> createState() {
return _OrganizationPageState();
}
}
class _OrganizationPageState extends State<_OrganizationPageUI> {
#override
Widget build(BuildContext context) {
Consumer<RatingService>(
builder: (context, data, child) {
Consumer<RatingService>(
return Row(
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 10, left: 10),
child: Text(daa.getData()
style: Theme.of(context).textTheme.bodyText2.apply(color: Colors.grey),
),
),
],
);
),
}
}
}
In OrganizationPage there is a AlerDialog, which allows the user to rate and save. When saved, it will call another method which will reload the data.
Widget _ratingDialog(double _rating) {
RatingService _ratingService =
Provider.of<RatingService>(context, listen: false);
Rating _rating = _ratingService.returnRating();
double _ratingValue = _ratingService.returnRating().rating;
return AlertDialog(
title: const Text("Your Rating"),
actions: [
new FlatButton(
child: const Text("Save"),
//onPressed: () => Navigator.pop(context),
onPressed: () async {
Rating rating = Rating(
idrating:
_rating.idrating != null ? _rating.idrating : null,
user: _user,
organization: widget.organization,
rating: _ratingValue,
dateCreated: DateTime.now().millisecondsSinceEpoch,
lastUpdated: DateTime.now().millisecondsSinceEpoch);
await _ratingService.saveOrUpdateRating(rating, authToken);
_loadRatingByUserAndOrganization(authToken);
_loadRatingValueByOrganization(authToken);
Navigator.pop(context);
},
),
],
);
}
Future _loadRatingByUserAndOrganization(String authToken) {
RatingService _ratingService =Provider.of<RatingService>(context, listen: false);
return _ratingService.getRatingByUserAndOrganization(
_authService.getDatabaseUser().user.iduser,
widget.organization.idorganization,
authToken);
}
RatingService
This is the class which is responsible for calling notifyListeners(). It will be triggered by the above AlertDialog and the expected behaviour is to reload data in both OrganizationPage and NearByPlacesPage
class RatingService with ChangeNotifier {
List<RatingValue> _ratingValueList ;
List<RatingValue> getData()
{
return _ratingValueList;
}
//Load rating by user and Organization
Future<void> getRatingByUserAndOrganization(int idUser, int organizationID, String authToken) async {
try {
var data = await http.get(
_navLinks.getRatingByUserAndOrganization(idUser, organizationID),
headers: {HttpHeaders.authorizationHeader: "Bearer $authToken"},
);
print(data.body);
_rating = Rating.fromJson(convert.json.decode(data.body));
notifyListeners();
} catch (error) {
print(error);
throw error;
}
}
}
What I have I done wrong?

Manage state of one page from another class

I'm building an app for training in Flutter and I'm actually stuck in the filter functionality.
I have a ListView where I fetch data from TheMovieDB API and a ModalBottomSheet with three FilterChips for selecting the filter criteria (popular, top rated and latest movies).
And here's where I'm stuck. I want to call the "_loadNextPage()" method when the user presses the "Done" button in the ModalBottomSheet through "performUpdate()" but I can't do it because they're not in the same class.
I'll post the code down below for better understanding.
class _HomePageState extends State<HomePage> {
RequestProvider _requestProvider = new RequestProvider();
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("FluttieDB"),
actions: <Widget>[
IconButton(
icon: Icon(Icons.filter_list),
onPressed: () => buildFilterBottomSheet(),
)
],
),
body: MovieList(_requestProvider, _currentFilter),
);
}
void buildFilterBottomSheet() {
showModalBottomSheet(
context: context,
builder: (builder) {
return Container(
height: 150.0,
decoration: BoxDecoration(color: Colors.white),
child: Column(
children: <Widget>[
buildFilterTitle(context),
Expanded(
child: _FilterChipRow(),
),
],
),
);
});
}
Widget buildFilterTitle(BuildContext context) {
return Container(
padding: const EdgeInsets.symmetric(horizontal: 12.0, vertical: 6.0),
alignment: Alignment.centerLeft,
height: 46.0,
decoration: BoxDecoration(color: Colors.blue),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Text(
"Filter by",
style: TextStyle(color: Colors.white, fontSize: 20.0),
),
OutlineButton(
onPressed: () => performUpdate(context),
padding: const EdgeInsets.all(0.0),
shape: const StadiumBorder(),
child: Text(
"Done",
style: TextStyle(color: Colors.white),
),
),
],
),
);
}
void performUpdate(BuildContext context) {
MovieList _movieList = new MovieList(_requestProvider, _currentFilter);
_movieList.createState()._loadNextPage();
Navigator.pop(context);
}
}
class MovieList extends StatefulWidget {
MovieList(this.provider, this.currentFilter, {Key key}) : super(key: key);
final RequestProvider provider;
final String currentFilter;
#override
_MovieListState createState() => new _MovieListState();
}
class _MovieListState extends State<MovieList> {
List<Movie> _movies = List();
int _pageNumber = 1;
LoadingState _loadingState = LoadingState.LOADING;
bool _isLoading = false;
_loadNextPage() async {
_isLoading = true;
try {
var nextMovies = await widget.provider
.provideMedia(widget.currentFilter, page: _pageNumber);
setState(() {
_loadingState = LoadingState.DONE;
_movies.addAll(nextMovies);
_isLoading = false;
_pageNumber++;
});
} catch (e) {
_isLoading = false;
if (_loadingState == LoadingState.LOADING) {
setState(() => _loadingState = LoadingState.ERROR);
}
}
}
#override
void initState() {
super.initState();
_loadNextPage();
}
#override
Widget build(BuildContext context) {
switch (_loadingState) {
case LoadingState.DONE:
return ListView.builder(
itemCount: _movies.length,
itemBuilder: (BuildContext context, int index) {
if (!_isLoading && index > (_movies.length * 0.7)) {
_loadNextPage();
}
return MovieListItem(_movies[index]);
});
case LoadingState.ERROR:
return Center(
child: Text("Error retrieving movies, check your connection"));
case LoadingState.LOADING:
return Center(child: CircularProgressIndicator());
default:
return Container();
}
}
}
As you can see, I did some experiments in the performUpdate() but it doesn't refresh the ListView with the selected option in the filters and I don't think it's the best way to achieve what I want.
Thanks and sorry if the question is a bit dumb. I'm a little bit newbie in Flutter.

Redux is a great state management library that originated with React and JS, but has been ported to Dart, and has a flutter specific library as well. Redux is a very powerful framework which uses a pub/sub system to allow your view to subscribe to changes to the model, while using a system of "actions" and "reducers" to update the model.
A great tutorial for getting up and running with Redux in Flutter can be found here
Alternatively you could look into the scoped model, which is another state management library for flutter. The scoped model is less capable, but for simple use cases may be more than adequate.
Further reading:
Understand and choose a state management solution
You Might Not Need Redux