How to reference variable in method in FutureBuilder (builder:)? - flutter

Question

I want to use the variable dbRef in inputData() in future Builder builder: you can see the variable in between asterisk .
void inputData() async {
FirebaseUser user = await FirebaseAuth.instance.currentUser();
final uid = user.uid;
final **dbRef** = FirebaseDatabase.instance.reference().child("Add Job Details").child(uid).child("Favorites");
}
#override
Widget build(BuildContext context) {
return FutureBuilder (
future: **dbRef**.once(),
builder: (context, AsyncSnapshot<DataSnapshot> snapshot) {
if (snapshot.hasData) {
List<Map<dynamic, dynamic>> list = [];
for (String key in snapshot.data.value.keys) {
list.add(snapshot.data.value[key]);
}

Answer 1

This is one more approach to tackle the problem.
The idea is to use a variable _loading and set it to true initially.
Now, after in your inputData() function, you can set it to false once you get the dbref.
Store dbref, the way I stored _myFuture in the code below i.e., globally within the class.
Use your _loading variable to return a progress bar if its true else return FutureBuilder with your dbref.once() in place. Now, that you have loaded it, it should be available at this point.
class MyWidget extends StatefulWidget {
#override
createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
// Is the future being loaded?
bool _loading;
// This is the future we will be using in our FutureBuilder.
// It is currently null and we will assign it in _loadMyFuture function.
// Until assigned, we will keep the _loading variable as true.
Future<String> _myFuture;
// Load the _myFuture with the future we are going to use in FutureBuilder
Future<void> _loadMyFuture() async {
// Fake the wait for 2 seconds
await Future.delayed(const Duration(seconds: 2));
// Our fake future that will take 2 seconds to return "Hello"
_myFuture = Future(() async {
await Future.delayed(const Duration(seconds: 2));
return "Hello";
});
}
// We initialize stuff here. Remember, initState is called once in the beginning so hot-reload wont make flutter call it again
#override
initState() {
super.initState();
_loading = true; // Start loading
_loadMyFuture().then((x) => setState(() => _loading = false)); // Set loading = false when the future is loaded
}
#override
Widget build(BuildContext context) {
// If loading, show loading bar
return _loading?_loader():FutureBuilder<String>(
future: _myFuture,
builder: (context, snapshot) {
if(!snapshot.hasData) return _loader(); // still loading but now it's due to the delay in _myFuture
else return Text(snapshot.data);
},
);
}
// A simple loading widget
Widget _loader() {
return Container(
child: CircularProgressIndicator(),
width: 30,
height: 30
);
}
}
Here is the output of this approach
This does the job but, you might need to do it for every class where you require your uid.
========================================
Here is the approach I described in the comments.
// Create a User Manager like this
class UserManager {
static String _uid;
static String get uid => _uid;
static Future<void> loadUID() async {
// Your loading code
await Future.delayed(const Duration(seconds: 5));
_uid = '1234'; // Let's assign it directly for the sake of this example
}
}
In your welcome screen:
class MyWidget extends StatefulWidget {
#override
createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
bool _loading = true;
#override
void initState() {
super.initState();
UserManager.loadUID().then((x) => setState(() => _loading = false));
}
#override
Widget build(BuildContext context) {
return _loading ? _loader() : Text('Welcome User ${UserManager.uid}!');
}
// A simple loading widget
Widget _loader() {
return Container(child: CircularProgressIndicator(), width: 30, height: 30);
}
}
The advantage of this method is that once you have loaded the uid, You can directly access it like this:
String uid = UserManager.uid;
thus eliminating use of futures.
Hope this helps!