Dart: Minimising access to Firebase in Flutter app - flutter

I have the following widget which builds a to-do list from a subcollection of a task given its document ID. The code is working fine.
Widget buildFoodList() {
return SizedBox(
child: Container(
padding: const EdgeInsets.all(10.0),
child: StreamBuilder<QuerySnapshot>(
stream: Firestore.instance.collection('tasks').document(documentID).collection('todo')
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError)
return new Text('Error: ${snapshot.error}');
switch (snapshot.connectionState) {
case ConnectionState.waiting:
return new Text('Loading...');
default:
return new ListView.builder(
shrinkWrap: true,
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) {
DocumentSnapshot ds = snapshot.data.documents[index];
return new Row(
children: <Widget>[
Expanded (child:Text(ds['deadline'].toString()) ),
Expanded (child:Text(ds['description']) ),
Expanded (child:Text("\$"+ds['quantity'].toString()) ),
],
);
},
);
}
},
)
),
);
}
As you can see, I am using a StreamBuilder. However, I know that the subcollection is not going to change. So the question is whether using StreamBuilder is an overkill, because using stream to listen can be a waste of resources and access to Firebase. More importantly, the cost of using Firebase is calculated on an access basis.
To summarise, the question is whether using StreamBuilder is necessary. If not, what is the alternative approach which can help to avoid unnecessary access to Firebase.
Thanks.

StreamBuilder is necessary in apps where you need to fetch any update , insert or delete in a firebase collection ( in this case ). An alternative can be the FutureBuilder that fetch the data once and then you can wrap in a Swipe to refresh ( and the user decides when needs to see new data).

Related

how to use two future builder in one page in flutter

In my Flutter app, I need to display two lists that are coming from the database, but I am having trouble getting both lists to display on the same screen. I am using two FutureBuilder widgets, but the first list is displaying correctly while the second list is still loading.
Here is the code I am using:
var future1 = FutureBuilder<List<QuranTextModel>>(
future: database.getQuranText(),
builder: (context, snapshot) {
if(snapshot.hasData){
return ScrollablePositionedList.builder(
itemScrollController: scrollToIndex,
itemCount: snapshot.data!.length,
initialScrollIndex: widget.position,
itemBuilder: (context, index) {
// Build the list item widget here
});
}else{
return const Center(child: CircularProgressIndicator(),);
}
}
);
var future2 = FutureBuilder<List<UrduTextModel>>(
future: database.getUrduTranlation(),
builder: (context, snapshot) {
if(snapshot.hasData){
return ScrollablePositionedList.builder(
itemScrollController: scrollToIndex,
itemCount: snapshot.data!.length,
initialScrollIndex: widget.position,
itemBuilder: (context, index) {
// Build the list item widget here
});
}else{
return const Center(child: CircularProgressIndicator(),);
}
}
);
Column(
children: [
SizedBox(
height: 200,
child: future1,
),
SizedBox(
height: 200,
child: future2,
),
],
)
The first FutureBuilder is used to build a list of QuranTextModel objects, and the second FutureBuilder is used to build a list of UrduTextModel objects. I am using a Column widget to display both lists, with each list contained within a SizedBox widget to give it a fixed height.
The issue I am having is that only the first list is displaying correctly, while the second list is still loading. How can I get both lists to display on the same screen?
Thank you for any help you can provide!
SingleChildScrollView(
child: Column(
children: [
SizedBox(
height: 200,
child: future1),
SizedBox(height: 200,child: future2,)
],
),
),
Try this.
also you have to check your future status before populate you can check that by using
if (snap.connectionState == ConnectionState.done) { your code. you can check does snpa has data in it. }
connection state has deferent states that can help you to make your UI more interactive

Flutter Firebase only let certain data be shown on list view builder

I am trying to only display certain data from a collection. In my example, I only want to show data in the list where the collection in name on firebase is equal to the name of the widget. I am unable to solve this problem
Expanded(
child: Container(
child: FutureBuilder(
future: getPosts(),
builder: (_,snapshot){
if(snapshot.data["name"]== widget.info.name){
return ListView.builder(
itemCount:
x,
itemBuilder: (_,index){
return ListTile(
title: Text(snapshot.data[index].data["name"]),
);
});
Expanded(
child: Container(
child: FutureBuilder(
future: getPosts(),
builder: (_,snapshot){
return ListView.builder(
itemCount:
snapshot.data,
itemBuilder: (_,index){
if(snapshot.data["name"]== widget.info.name){
return ListTile(
title:Text(snapshot.data[index].data["name"]),
);
}else{
return Container();
}
})}))
);
A better option will be to pass the widget name in the getPosts() function you defined and update the firebase query to do the filtering. This way it be much faster as firebase does the require indexing and will do the filtering in O(len(filtered_elements)) rather than current time complexity of O(len(all_elements)).

Load data from the Database

I followed the chat development app tutorial on the Flutter page, it's a single user app. I have now been able to create a database and store data in the database, but I now have a conundrum that I'm unable to resolve.
I'm loading the chats from the database using FutureBuilder
FutureBuilder(
future: _requestSqlDataAsync(),
builder: (context, snapshot) {
if (snapshot.data == null) {
return Container(
child: Center(
child: Text("Loading...."),
),
);
}
else {
return ListView.builder(
padding: EdgeInsets.all(8.0),
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int index) {
return Text(snapshot.data[index].chat);
}
);
It successfully loads the data from the database but then I'm unable to pass submit new chats from TextController to the display widget in the following manner:
ListView.builder(
padding: EdgeInsets.all(8.0),
reverse: true,
itemBuilder: (_, int index) => _message[index],
itemCount: _message.length,
)
where _message is the widget that combines the data from the TextController along with animation, to display the chat.
Could anyone please guide me as to how I can load the data from the database and then pass the control for the chats to be loaded.

Flutter Firestore returning null (retrieve data from subcollection)

What do I want it to do
I want to fetch a list of the amount of photo's a user has stored in it's profile updated in realtime.
I want my code to fetch the links from a user profile but I am constantly getting an error.
The value "Text("${document['link']}")" gives null.
What have I tried
Read and applied every problem/solution on stackoverflow on this issue
My code
I already have another streambuilder which is used to fetch the names of the instances so that's where the other DocumentSnapshot is coming from. Now I just want a streambuilder which focusses on the pictures.
Widget imageList(DocumentSnapshot document //I use this to fetch the current document ID) {
print(_uploadedFileURL);
return StreamBuilder(
stream: Firestore.instance
.collection('Test')
.document(document.documentID).collection('foto')
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return Text("Loading");
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) =>
_imageList(context, snapshot.data.documents[index]));
},
);
}
//Widget to show the Text but this returns null
Widget _imageList(BuildContext context, DocumentSnapshot document) {
return Card(
child: prefix0.Column(
children: <Widget>[
prefix0.Text("${document['link']}")
],
),
);
}
Get data from the doc snapshot with its data method...
prefix0.Text("${document.data()['link']}")

Nested ListView, StreamBuilder and Subcollection

I'm trying to create a nested ListView, but don't know, if I can combine 2 streambuilders in a nested view, as it doesn't work. In the second StreamBuilder with the subcollection query, no data seems to be returned and I can't figure out why.
When I hardcode the document id I don't get any error, but still the query doesn't seem to return any data.
Does anybody know, how to construct a nested listview with streambuilders and Firestore?
List<Widget> buildStreamedListView() {
return [ StreamBuilder(
stream: Firestore.instance.collection('course')
.document(widget.data.documentID)
.collection('section')
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text("Loading...");
return Expanded(child: ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) {
//return buildListItem(context, snapshot.data.documents[index]);
return Card(
child: ExpansionTile(
title: Text(snapshot.data.documents[index]['name']),
children: <Widget>[
StreamBuilder(
stream: Firestore.instance.collection('course')
.document(widget.data.documentID)
.collection('section')
.document('4CjAZEQ416NYpu3ra3OE')
.collection('page')
.snapshots(),
builder: (context, snap) {
return ListView.builder(
shrinkWrap: true,
itemCount: snap.data.documents.length,
itemBuilder: (context, index) {
return Text('Hello you');
}
);
}
),
],
),
);
}
));
},
)];
}
The reason that I had strange errors was, that in the second builder function I didn't add the following code:
if (!snapshot.hasData) return const Text("Loading...");
Once I added it, it worked. Seems the data was just not ready yet, hence it couldn't be read and hence the error.
Be careful to also test for snap.hasData() in your nested StreamBuilder.