here I'm trying to get the top 10 names only from my firebase firestore,
and I searched on how I do it with the listview that I have, but I get to nowhere.
so I thought about getting the id of my documents instead.
In my firestore I gave the top 10 documents IDs from 1 to 10, now I'm stuck and I have no idea how to do it. please help.
static int id = 1;
StreamBuilder<QuerySnapshot>(
stream: fireStore.collection(path).snapshots(),
builder: (context, snapshot) {
if(!snapshot.hasData){
return Center(
child: CircularProgressIndicator(
backgroundColor: Colors.blueAccent,
),
);
}
List<InfoBox> ancients = [];
try {
final collection = snapshot.data!.docs;
for (var collect in collection) {
final name = collect['Name'];
final image = collect['Image'];
final collectionWidget = InfoBox(
ancientName: name,
ancientImage: image
);
ancients.add(collectionWidget);
}
}catch(e){
print('problems in stream builder \n error : $e');
}
return Expanded(
child:ListView(
children: ancients,
)
);
},
);
You are probably searching for limit() function. According to the documentation:
To limit the number of documents returned from a query, use the limit method on a collection reference
You can implement it like this:
fireStore.collection(path).limit(10).snapshots();
Change your ListView to this List if else everything is ok and u are getting data in list then this will work.
ListView.builder(
itemCount: ancients.length,
itemBuilder: (BuildContext context, int index) {
return ListTile(
leading: new Image.network(ancients[index].ancientImage),
title: new Text(ancients[index].ancientName),
)
},
)
Related
I have a build on Firebase Firestore like this:
In the structure here, there are 2 ArrayLists. I want to display what will be done from 2 ArrayLists as ListTile.
I tried a code like this:
Expanded(
child: StreamBuilder <QuerySnapshot>(
stream: FirebaseFirestore.instance.collection("users").doc(FirebaseAuth.instance.currentUser.uid).collection("yapilacaklar").snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return LinearProgressIndicator();
return Expanded(
child: _buildList(snapshot.data),
);
},
)
),
Widget _buildList(QuerySnapshot snapshot) {
return ListView.builder(
itemCount: snapshot.docs.length,
itemBuilder: (context, index) {
final doc = snapshot.docs[index];
return ListTile(
title: Text(doc["yapilacaklar"].toString()),
);
},
);
}
These codes I tried do not give an error, but they do not show in any Widget. How can I do what I want? Thanks in advance for the help.
I believe the issue is the '.collection("yapilacaklar")'. It will try to find a collection with the id "yapilacaklar" and your user doc doesn't have any collections. Yapilacaklar, in this case, is a field in the document. Try getting the snapshots of the actual document and then creating a ListView from the array in the yapilacaklar field.
The flutterfire documentation is very helpful for reading firestore data: https://firebase.flutter.dev/docs/firestore/usage/#read-data
I am trying to get user avatar from firebase storage, however, my current code only returns Instance of 'Future<String>' even I am using async/await as below. How is it possible to get actual download URL as String, rather Instance of Future so I can access the data from CachedNewtworkImage?
this is the function that calls getAvatarDownloadUrl with current passed firebase user instance.
myViewModel
FutureOr<String> getAvatarUrl(User user) async {
var snapshot = await _ref
.read(firebaseStoreRepositoryProvider)
.getAvatarDownloadUrl(user.code);
if (snapshot != null) {
print("avatar url: $snapshot");
}
return snapshot;
}
getAvatarURL is basically first calling firebase firestore reference then try to access to the downloadURL, if there is no user data, simply returns null.
Future<String> getAvatarDownloadUrl(String code) async {
Reference _ref =
storage.ref().child("users").child(code).child("asset.jpeg");
try {
String url = await _ref.getDownloadURL();
return url;
} on FirebaseException catch (e) {
print(e.code);
return null;
}
}
I am calling these function from HookWidget called ShowAvatar.
To show current user avatar, I use useProvider and useFuture to actually use the data from the database, and this code works with no problem.
However, once I want to get downloardURL from list of users (inside of ListView using index),
class ShowAvatar extends HookWidget {
// some constructors...
#override
Widget build(BuildContext context) {
// get firebase user instance
final user = useProvider(accountProvider.state).user;
// get user avatar data as Future<String>
final userLogo = useProvider(firebaseStoreRepositoryProvider)
.getAvatarDownloadUrl(user.code);
// get actual user data as String
final snapshot = useFuture(userLogo);
// to access above functions inside of ListView
final viewModel = useProvider(myViewModel);
return SingleChildScrollView(
physics: AlwaysScrollableScrollPhysics(),
child: Container(
padding: const EdgeInsets.all(24),
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
SizedBox(
height: 100,
width: 100,
child: Avatar(
avatarUrl: snapshot.data, // **this avatar works!!!** so useProvider & useFuture is working
),
),
SizedBox(height: 32),
ListView.builder(
shrinkWrap: true,
physics: NeverScrollableScrollPhysics(),
itemBuilder: (context, index) {
return Center(
child: Column(
children: [
SizedBox(
height: 100,
width: 100,
child: Avatar(
avatarUrl: viewModel
.getAvatarUrl(goldWinners[index].user)
.toString(), // ** this avatar data is not String but Instance of Future<String>
),
),
),
],
),
);
},
itemCount: goldWinners.length,
),
Avatar() is simple statelesswidget which returns ClipRRect if avatarURL is not existed (null), it returns simplace placeholder otherwise returns user avatar that we just get from firebase storage.
However, since users from ListView's avatarUrl is Instance of Future<String> I can't correctly show user avatar.
I tried to convert the instance to String multiple times by adding .toString(), but it didn't work.
class Avatar extends StatelessWidget {
final String avatarUrl;
final double radius;
final BoxFit fit;
Avatar({Key key, this.avatarUrl, this.radius = 16, this.fit})
: super(key: key);
#override
Widget build(BuildContext context) {
print('this is avatar url : ' + avatarUrl.toString());
return avatarUrl == null
? ClipRRect(
borderRadius: BorderRadius.circular(radius),
child: Image.asset(
"assets/images/avatar_placeholder.png",
fit: fit,
),
)
: ClipRRect(
borderRadius: BorderRadius.circular(radius),
child: CachedNetworkImage(
imageUrl: avatarUrl.toString(),
placeholder: (_, url) => Skeleton(radius: radius),
errorWidget: (_, url, error) => Icon(Icons.error),
fit: fit,
));
}
}
Since the download URL is asynchronously determined, it is returned as Future<String> from your getAvatarUrl method. To display a value from a Future, use a FutureBuilder widget like this:
child: FutureBuilder<String>(
future: viewModel.getAvatarUrl(goldWinners[index].user),
builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
return snapshot.hashData
? Avatar(avatarUrl: snapshot.data)
: Text("Loading URL...")
}
)
Frank actually you gave an good start but there are some improvements we can do to handle the errors properly,
new FutureBuilder(
future: //future you need to pass,
builder: (context, snapshot) {
if (snapshot.hasData) {
return new ListView.builder(
itemCount: snapshot.data.docs.length,
itemBuilder: (context, i) {
DocumentSnapshot ds = snapshot.data.docs[i];
return //the data you need to return using /*ds.data()['field value of doc']*/
});
} else if (snapshot.hasError) {
// Handle the error and stop rendering
GToast(
message:
'Error while fetching data : ${snapshot.error}',
type: true)
.toast();
return new Center(
child: new CircularProgressIndicator(),
);
} else {
// Wait for the data to fecth
return new Center(
child: new CircularProgressIndicator(),
);
}
}),
Now if you are using a text widget as a return statement in case of errors it will be rendered forever. Incase of Progress Indicators, you will exactly know if it is an error it will show the progress indicator and then stop the widget rendering.
else if (snapshot.hasError) {
}
else {
}
above statement renders until, if there is an error or the builder finished fetching the results and ready to show the result widget.
I am new to firebase and I am wondering how would you access specific data. Ill give you an example, BTW I am using flutter.
Say I am creating data like this. I making a table of posts or I guess in firebase it'd be just a json array. In this json array I have 4 pieces of data state, city, post which as of right now just represents a simple message, and also timestamp.
So my question is how can I get a filtered version of my posts with a given city and state? Is there something special you can do in firebase? or would I have to do the filtering when I am building the list view?
I know FirebaseDatabase().reference().child('posts'); can access all of the posts.
var _firebaseRef = FirebaseDatabase().reference().child('posts');
_firebaseRef.push().set({
"state": state,
"city": city,
"post": post,
"timestamp": DateTime.now().millisecondsSinceEpoch
});
The code in the question means you are adding data, not retrieving. If you want to retrieve data according to a specific city then do the following query:
var dbRef = FirebaseDatabase().reference().child('posts');
dbRef.orderByChild("city").equalTo("city_name").once();
once() returns a Future so you can use the FutureBuilder to get the data from the above query.
Use Future Builder to fetch data to listview
create getPost() method first to return qn
Future getPosts() async {
var firestore = Firestore.instance;
QuerySnapshot qn = await firestore.collection("your_collecttion_name").getDocuments();
return qn.documents;
}
after that use, future builder to fetch data
return Container(
child: FutureBuilder(
future: getPosts(),
builder: (_, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Center(
child: Text("Loading..."),
);
} else {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (_, index) {
return Column(
children: <Widget>[
Text(
snapshot.data[index].data['your_data_field'] //name,age etc..
.toString(),
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500),
),]
),}
),
});
I'm building an app in Flutter in which I have data stored in the Firebase Realtime Database. I want to fetch those data in my app.
Now, Because of breaking changes made few months ago I'm unable to find new articles or video which might help but all I find are old ones so if anyone here can help me?
variable for the list
final dbRef = FirebaseDatabase.instance.reference().child("workshops");
now for showing the data I'm trying like this
return FutureBuilder(
future: dbRef.once(),
builder: (context,AsyncSnapshot<DataSnapshot> snapshot){
if(snapshot.hasData){
workshopList.clear();
Map<dynamic, dynamic> values = snapshot.data.value;
values.forEach((key,values){
workshopList.add(values);
});
}
return ListView.builder(
shrinkWrap: true,
itemCount: workshopList.length,
itemBuilder: (BuildContext context, index){
return Card(
child: Center(
child: Column(
children: [
Text("name "+ workshopList[index].workshopName)
],
),
),
);
},
);
}
);
For declaring list I was doing like this
List<Workshop> worskshopList = [];
but what worked for me was
List<Map<dynamic,dynamic>> workshopList = [];
And now for showing the data I am using
workshopList[index].workshopName
now problem with this is that I am not referencing database's workshopname but my model class' workshop name so I am getting nowhere.
now what worked for me was
workshopList[index]["workshopname"]
now from the old list I can't use like list[index][""] it will give an error like "[]" is not defined for the list.
I'd like to check if a collection (the users collection) exists in the Firestore database or not. But I cannot find any means of doing that. If the collection exists, I would like to stream its documents, otherwise an empty stream as you see in the following method
- Is there any way to find a collection exists without getting its snapshots?
- Why break; or yield* Stream.empty() hangs the stream, like an endless stream!
Stream<userInfo> getCurrentUserInfos() async* {
final String usersCollectionPath = "users";
Stream<QuerySnapshot> snapshots = Firestore.instance.collection(usersCollectionPath).snapshots();
snapshots.isEmpty.then((hasNoUserCollection) {
// Although I don't have 'users' collection
// in my database but I never reach this point!
// i.e. hasNoUserCollection is always FALSE!
if(hasNoUserCollection) {
print("users collection doesn't exist, create it!");
// next line (i.e. `break;`) hangs the tool!
// And sometimes hangs the VSCode's IDE as well, if I have a breakpoint on it!!!
break;
// I tried yielding an empty stream instead of break, again another hang!
// yield* Stream<userInfo>.empty();
} else {
// previous stream is dead, so create it again!
snapshots = Firestore.instance.collection(usersCollectionPath ).snapshots();
await for (QuerySnapshot snap in snapshots) {
for (DocumentSnapshot userDoc in snap.documents) {
yield (new userInfo.fromQuerySnapshot(userDoc));
}
}
});
}
Now even a try-catch block cannot catch what's gone wrong, when the stream is empty!
try{
getCurrentUserInfos().last.then((userInfolastOne) {
print("last one: $lastOne.name");
});
// the following line (i.e. await ...) at least doesn't hang and
// `catch` block is able to catch the error `Bad state: No element`,
// when the stream is empty
//
// userInfo lastOne = await stream.last;
} catch (ex) {
print ("ex: $ex");
}
There is no API to detect if a collection exists. In fact: a collection in Firestore only exists if there are documents in it.
The cheapest check I can think of is doing a query for a single document, and then checking if that query has any results.
Okay, maybe I figured it out
final snapshot = await Firestore.instance.collection(collectionName).getDocuments();
if (snapshot.documents.length == 0) {
//Doesn't exist
}
This worked for me
As stated by #Frank, a collection in Firestore gets deleted if no Documents exist in it.
However, I understand that there might be cases where you want to keep a history of the collection modification/ creation events, or let's say for some reason prevent Collections from being deleted.
Or for example, you want to know when a collection was created in the first place. Normally, if the Documents are deleted, and then the Collection gets created again, you will not know the initial creation date.
A workaround I can think of is the following:
Initialize each collection you want with a Document that will be specifically for keeping generic info about that collection.
For example:
This way, even if all other Documents in the Collection are deleted, you'll still keep the Collection in addition to some info that might be handy if In the future you need to get some history info about the Collection.
So to know if a Collection exists of no, you can run a query that checks for a field in Info Documents (eg CollectionInfo.exists) to know which Collections have been already created.
This is a sample from one of my projects. You can use snapshot.data!.docs.isEmpty to check if a collection has data or not.
StreamBuilder(
stream: _billGroupStream,
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) {
return const Center(
child: Text('Something went wrong'),
);
} else if (snapshot.connectionState == ConnectionState.waiting) {
return Center(
child: Column(
children: const [
LinearProgressIndicator(),
Text('Loading data, please wait...'),
],
),
);
} else if (!snapshot.hasData) {
return const Center(child: CircularProgressIndicator());
} else if (snapshot.data!.docs.isEmpty) {
return const Center(
child: Text(
'Huh!! Looks like you have no transactions yet!' ,
textAlign: TextAlign.center,
style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18),
),
);
} else if (snapshot.connectionState == ConnectionState.active) {
final List<DocumentSnapshot> docs = snapshot.data!.docs;
return ListView.builder(
shrinkWrap: true,
restorationId: 'billModeList',
itemCount: snapshot.data!.docs.length,
itemBuilder: (context, index) {
///This document snapshot is used for determining the unique id for update and delete methods
final DocumentSnapshot doc = docs[index];
//final DocumentSnapshot doc = snapshot.data!.docs[index];
///This [BillModel] converted data is used to build widgets
final BillModel billModel = doc.data()! as BillModel;
return Dismissible(
onDismissed: (direction) {
_remoteStorageService.deleteItemFromGroup(
widget.uri, doc.id);
setState(() {
docs.removeAt(index);
});
},
background: Container(
color: Colors.red,
child: const Icon(Icons.delete_forever_sharp),
),
key: Key(doc.id),
child: Card(
elevation: 3,
shadowColor: Colors.teal.withOpacity(.5),
child: ListTile(
leading:
const CircleAvatar(child: Icon(Icons.attach_money)),
title: Text(billModel.name),
subtitle: Text(billModel.category ?? ''),
trailing: Text(billModel.amount.toString()),
),
),
);
},
);
}
return const CircularProgressIndicator();
},
),