Flutter: I'm using Streambuilder to listen to Firestore data which works great.
However, what I would like to do is to notify the user when certain conditions in Firestore changes, let him respond and write that back to Firestore.
Doable (in Flutter/Dart)?
Thanks in advance.
Best,
/j
StreamBuilder(
stream: Firestore.instance.collection('users').snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text('Loading...');
List<DocumentSnapshot> documents = snapshot.data.documents;
documents.forEach((doc) {
if (doc['Invited']) {
**// notify current user that he is invited,
// let him reply yes/no, write that value back to Firestore**
}
}
},
);
Is there a point why you dont want to use Firebase Messaging?
1) Firestore triggers a Notification
2) Your App recieve the notification
3) Your app handle the notification, it should be possible that the user dont see the notification in the status bar.
If i understand you correctly you want to update something as soon as the user receives an invitation. You can do this by using code like this:
Future<Null> updateUser{
#required String userId,
bool accepted,
}) {
assert(userId != null && userId.isNotEmpty);
// create map that contains all fields to update
Map<String, dynamic> dataToUpdate = {
"accepted": accepted,
};
// get the reference to the user you want to update
final userRef = references.users(userId);
// update the user
return userRef.updateData(dataToUpdate);
}
You can get the reference from your document by using doc.reference. The Future will complete if the update was successful or terminate with an error if something went wrong.
Related
After defining a variable ("xyz" at screenshot), I fetched some data on my firestore database, then changed that variable value to data i fetched from firestore. When I print the changed variable with "print()" it appears at "Run" the value I fetched, which is what I want. But when I run the app, the text I assigned as changed variable appears on the screen with old value like I never changed it after defining. the code
When I print(xyz); it appears as the data from firestore, so there is no problem at database connection. I just want to update the value appears at screen too.
you could also listen to those snapshots without using StreamBuilder or any Flutter widget with the listen() method like this:
final fieldValue = "initial value";
FirebaseFirestore.instance
.doc(documentPath)
.snapshots()
.listen((snapshot) {
final data = snapshot.data() as Map<String, dynamic>;
fieldValue = data["field"];
print(fieldValue);
});
the fieldValue will be updated now every time an update happens to the document, and it will print it automatically in the console with the print()
as I see in the screenshot, you're getting your document's data with a Future, and the Future is useful when you need to call data just once :
FirebaseFirestore.instance.doc(documentPath).get(); // Future
FutureBuilder<DocumentSnapshot>(
future: FirebaseFirestore.instance.doc(documentPath).get(),
builder: (context, AsyncSnapshot<DocumentSnapshot> snapshot) {
if (snapshot.hasData) {
return Text("${snapshot.data!.data()}");
}
return Text("something else");
},
);
This will get the snapshot only once, even if you updated the document data, nothing will update on the screen until you make manually a new request to get another snapshot.
well the Firebase SDK for Flutter provide also Stream of snapshots for DocumentSnapshot and CollectionSnapshot, which listen directly to it, so whenever you have an update on your target, that stream will be notified and provide a new snapshot for that new updated data, and you can use it like this:
FirebaseFirestore.instance.doc(documentPath).snapshots(), // Stream
StreamBuilder<DocumentSnapshot>(
stream: FirebaseFirestore.instance.doc(documentPath).snapshots(), // Stream
builder: (context, AsyncSnapshot<DocumentSnapshot> snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
final currentData = snapshot.data!.data() as Map<String, dynamic>;
final fieldValue = currentData["fieldString"];
return Text("$fieldValue");
}
return Text("something else");
},
);
change fieldString with your field name to get its value.
Now every update you do to the DocumentSnapshot, the StreamBuilder will get that new snapshot from the Stream and update the UI based on it.
Hope this helps!
I am facing a problem with Streambuilder.
The workflow of my app is like there is a list of items when I press on add to favorites it adds the item to firestore. Then I am fetching data from firestore using stream and showing it on another screen using stream builder.
The problem is that the stream builder is empty when I hot reload the app the data shows perfectly.
this is the part where I am calling stream method
this is streambuilder
Thanks.
Try removing the extra variable resultStream and directly use the function DatabaseManager.getUserCurrency() in your StreamBuilder like this:
StreamBuilder(
stream: DatabaseManager.getUserCurrency(context),
builder: (context, snapshot){...}
)
if this does not fix the issue, check your getUserCurrency() function for errors. This is an example for getting a Stream from Firestore:
Stream<UserData> getUserData(String uid) {
try {
return userCollection
.doc(uid)
.snapshots()
.map((event) => event?.data() != null ? UserData.fromMap(event.data()) : null);
} catch (e) {
print(e);
return null;
}
}
Additionally you normally don’t have to await a Stream, which might cause the issue in your case, because you are calling the async function in your initState.
I am trying to get a bool value from Firestore when the app is being initialized: it returns True if it is "like" and False if it is not "like". Every time a user likes/unlikes a post, a database (called userFavorites) is being created or update on Firestore. The userFavorite database is composed of: document (user's ID), collection ('posts'), document (post's ID), collection (isLiked: true OR isLiked: false). So when initializing the app, I'm trying to get access to this True/False for each of the posts that are being displayed on the UI (if the user has never liked or unliked the post, the value for this bool will automatically be False).
I would really appreciate if you can give me feedback/corrections on the code I use to get the True/False bool value from Firestore, because even though I am not getting any errors, the bool value on my IU is Null, and I don't know whether I made an error in this part of my code or in another part.
Here is the code I used:
class HomeFeed extends StatelessWidget {
final user = FirebaseAuth.instance.currentUser;
ValueKey valueKey;
Future<DocumentSnapshot> getDocumentSnapshotForCurrentUserLikes(String userId, String documentId) async {
final String userId = user.uid;
final String documentId = valueKey.value;
return await FirebaseFirestore.instance.collection('userFavorites').doc(userId).collection('posts').doc(documentId).get();
}
bool getCurrentUserLikesValue(DocumentSnapshot documentSnapshotForCurrentUserLikes) {
return documentSnapshotForCurrentUserLikes.data()['isLiked'];
}
#override
Widget build(BuildContext context) {
return StreamBuilder(
stream: FirebaseFirestore.instance.collection('post').doc('Post in Feed').collection('posts').orderBy('createdAt', descending: true,).snapshots(),
builder: (ctx, AsyncSnapshot<QuerySnapshot> postSnapshot) {
if (postSnapshot.connectionState == ConnectionState.waiting) {
return Center(
child: CircularProgressIndicator(),
);
}
final postDocs = postSnapshot.data.docs;
return ListView.builder(
reverse: false,
itemCount: postDocs.length,
itemBuilder: (ctx, index) {
ValueKey valueKey = ValueKey(postDocs[index].id);
return Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
child: PostContainer(
user.uid,
postDocs[index].data()['likes'],
getCurrentUserLikesValue(postDocs[index]) == null ? false : getCurrentUserLikesValue(postDocs[index]),
key: valueKey,
),
),
);
},
);
},
);
}
}
Thank you for the input! Do you mean using something like this:
IconButton(
icon: Icon(
isLiked == true ? Icons.favorite : Icons.favorite_border,
color: Colors.red,
size: 25.0,
),
onPressed: () async{
DocumentReference docRef = FirebaseFirestore.instance.collection('userFavorites').doc(this.widget.userId);
DocumentSnapshot doc = await docRef.get();
List userLikedPosts = doc.data['userLikedPosts'];
if(userLikedPosts.contains(documentId)==true) {
docRef.update({'userLikedPosts' : FieldValue.arrayRemove([documentId])});
} else {
docRef.update({'userLikedPosts' : FieldValue.arrayUnion([documentId])});
}
If this is kind of code you are referring to, how can I use it with "set", instead of "get" (because if I use "get", the user reference would have to be created in Firebase beforehand for every user, which would be inefficient)? Also for doc.data['userLikedPosts'], I get an error for ['userLikedPosts'], which says "The operator '[]' isn't defined for the type 'Map<String, dynamic> Function()'. Try defining the operator '[]'." How would you solve this? Thanks a lot for the help!
Hello! I have been researching and working on it for a while, and the problem that I am having is that I am not able to get and display the T/F bool value from the Firestore database into the UI each time a post is initialized (or seen on the screen). What code could I use to do that? I would really appreciate your help here. Thanks!
You're making your life much harder than it should be:
Consider a db structure like this:
userFavorite (collection)
|---{userId} (document)
|--- liked_posts (Array) [array of post Ids the posts the user liked]
|--- ['postA', 'postB', 'post3131',...]
By doing it this way, for each postID, you can just check if it exists in that liked_posts array. This a cleaner way to do things. You don't need extra document and collection levels.
When the user clicks a "like" on a post, you can use ArrayUnion to add that postId to the liked_posts field of that user.
Update:
Sorry, I can't help you with Flutter code. All I can say is this:
? did the user like the post? If so, you can update the userLikedPosts (Array) field WITHOUT reading it first. With ArrayUnion, if the postId is within that array, it won't be added, if it's not there it will be added, the other elements in the Array will not be changed.
? did the user dislike the post? If so, you can update userLikedPosts (Array) field WITHOUT reading it first. With ArrayRemove, if the postId is within that array, it will be removed, if it's not there then nothing happens, the other elements in the Array will not be changed.
In your place, I would not use update():
docRef.update({'userLikedPosts' : FieldValue.arrayRemove([documentId])});
Instead, I would use set() with {merge:true}:
docRef.set( {'userLikedPosts' : FieldValue.arrayRemove([documentId])}, {merge:true} );
ArrayUnion/ArrayRemove works flawlessly with set() and won't rewrite the array. Also, if the document doesn't exist, then it will be created automatically.
Sorry I can't help you with actual Flutter code, but my main point is that you do not need to read the document containing the userLikedPosts Array when responding to LIKE/DISLIKE user actions. You only need to read it when displaying whether or not the post is liked by the user, and only on subsequent post page visits. When the user presses like, you can respond in the UI immediately and the logic above to update the db with set/merge:true and ArrayUnion.
I want to define and invoke a function in Flutter to get required values from Firebase.
In the below code I have defined getCourseDetails() function and invoking it in the container by passing a parameter to get the value.
The Course_Details collection has many documents with course_id's which has attribute with name (course_name, subtitle). I use these values to build a listview cards in next steps.
I am able to get the values from the function using async await, but for some reason the values keeps on updating and never stops. It kind of goes to loop and keeps on running. I added print statements to check and it keeps on running and printing.
Please let me know what wrong I am doing here or how to define function here to avoid the issue. Thanks
class _CourseProgressListState extends State<CourseProgressList> {
String course_name, subtitle;
getCourseDetails(course_id_pass) async {
DocumentSnapshot document = await Firestore.instance.collection('Course_Details').document(course_id_pass).get();
setState(() {
course_name = document.data['course_name'];
subtitle = document.data['subtitle'];
});
}
#override
Widget build(BuildContext context) {
return Container(
child: StreamBuilder(
stream: Firestore.instance.collection('Enrolling_Courses').where('student_id', isEqualTo: widget.id).snapshots(),
builder: (context, snapshot) {
if (snapshot.data == null) return Text('no data');
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (_, int index) {
var course_details = snapshot.data.documents[index];
getCourseDetails(course_details['course_id']);
Application Flow
On first build of CourseProgressList the Widget State _CourseProgressListState is loaded. This State in the build method uses a StreamBuilder to retrieve all documents from the firestore. As soon as the documents are received the StreamBuilder attempts to build the ListView using the ListViewBuilder.
In the ListViewBuilder you make the async call to getCourseDetails(course_details['course_id']); which when complete populates two attributes String course_name, subtitle;
The problem starts here
Problem
When you call
setState(() {
course_name = document.data['course_name'];
subtitle = document.data['subtitle'];
});
you trigger a Widget rebuild and so the process starts over again to rebuild the entire widget.
NB. refreshing state of a stateful widget will trigger a widget rebuild
NB. Firestore.instance.collection('Enrolling_Courses').where('student_id', isEqualTo: widget.id).snapshots() returns a stream of realtime changes implying that your List will also refresh each time there is a change to this collection
Recommendations
If you do not need to call the setState try not to call the setState.
You could let getCourseDetails(course_id_pass) return a Future/Stream with the values desired and use another FutureBuilder/StreamBuilder in your ListViewBuilder to return each ListViewItem. Your user may appreciate seeing some items instead of waiting for all the course details to be available
Abstract your request to firestore in a repository/provider or another function/class which will do the entire workload, i.e retrieving course ids then subsequently the course details and returning a Future<List<Course>> / Stream<List<Course>> for your main StreamBuilder in this widget (see reference snippet below as a guide and requires testing)
Reference Snippet
Your abstraction could look something like this but this decision is up to you. There are many software design patterns to consider or you could just start by getting it working.
//let's say we had a class Course
class Course {
String courseId;
String courseName;
String subTitle;
Course({this.courseId,this.courseName,this.subTitle})
}
Stream<List<Course>> getStudentCourses(int studentId){
return Firestore.instance
.collection('Enrolling_Courses')
.where('student_id', isEqualTo: studentId)
.snapshots()
//extract documents from snapshot
.map(snapshot => snapshot?.data ?? [])
//we will then request details for each document
.map(documents =>
/*because this is an asynchronous request for several
items which we are all interested in at the same time, we can wrap
this in
a Future.wait and retrieve the results of all as a list
*/
Future.wait(
documents.map(document =>
//making a request to firestore for each document
Firestore.instance
.collection('Course_Details')
.document(document['course_id'])
.get()
/* making a final transformation turning
each document into a Course item which we can easily pass to our
ListBuilder/Widgets
*/
.then(courseItem => Course(
courseId:document['course_id'],
courseName:
courseItem.data['course_name'],
subTitle:
courseItem.data['subtitle']
)
)
)
)
);
}
References/Resources
FutureBuilder - https://api.flutter.dev/flutter/widgets/FutureBuilder-class.html
StreamBuilder - https://api.flutter.dev/flutter/widgets/StreamBuilder-class.html
Future.wait - https://api.flutter.dev/flutter/dart-async/Future/wait.html
My app structure is a little bit mess, but I have to add this patch first and then I'll restructure the entire logic. The thing is I first check if there's a firebase user, then if there is one I use StreamBuilder to get the current user profile from Firestore, then I have the _firebaseMessaging.configure method because onLaunch and onResume I use this callback:
void _navigateToGestorResevas(Map<String, dynamic> message, User currentUser) {
Navigator.push(context,
MaterialPageRoute(builder: (context) =>
GestorScreen(user: currentUser)));
}
Because I need to send the User to this screen where he fetch the message from firebase.
onResume this works fine, but onLaunch it goes to the screen and fetch the data but there are like 20 seconds where there are some kind of glitch. It switch like 20-30 times between two states where I have and no have snapshot data in this _initState func:
final snapshot = await _dbRef.child('mensajes').child(widget.user.id).once();
if (snapshot.value != null) {
setState(() {
hayMensajes = true;
});
final data = snapshot.value;
for (var entry in data.entries) {
Message message = Message.fromJson(entry.value);
setState(() {
message.add(message);
});
}
} else {
setState(() {
hayMensajes = false;
});
}
Anyone have an idea what am I doing wrong?
If I am not mistaken, there are some active issues about FCM onLaunch callback with flutter. Some of them are still not fixed. One of the problems most people had to face was that onLaunch callback being called multiple times. I don't know why it happened, but as in your case, you can possibly get rid of the issue by some temporary fixes.
If the same screen is getting pushed over and over again, and glitching, you can pop the stack until it reaches the one you meant to open and set a condition to push navigator only if the new route is different from the old one. Using the named routes,
Navigator.popUntil(context, ModalRoute.withName(routeName));
if (ModalRoute.of(context).settings.name != routeName) {
Navigator.pushNamed(context, routeName);
}
I am not sure if that was the problem you asked, but I hope at least my answer helps somehow.