Flutter: ScrollController initialScrollOffset not working - flutter

Question

I'm trying to initialize a SingleChildScrollView to start at a certain position with a custom ScrollController. I thought I could use initialScrollOffset and set an initial value in the init method. But somehow when the SingleChildScrollView renders, it only jumps to initialOffset at first build, then when I navigate to another instance of this Widget it doesn't jump to the initialOffset position.
I don't know why, and if I'm lucky maybe one of you have the answer.
Here's my code:
class Artiklar extends StatefulWidget {
final String path;
final double arguments;
Artiklar({
this.path,
this.arguments,
});
#override
_ArtiklarState createState() => _ArtiklarState(arguments: arguments);
}
class _ArtiklarState extends State<Artiklar> {
final double arguments;
_ArtiklarState({this.arguments});
ScrollController _scrollController;
double scrollPosition;
#override
void initState() {
super.initState();
double initialOffset = arguments != null ? arguments : 22.2;
_scrollController = ScrollController(initialScrollOffset: initialOffset);
}
#override
void dispose() {
_scrollController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
final bool isAdmin = Provider.of<bool>(context) ?? false;
var pathElements = widget.path.split('/');
String tag;
if (pathElements.length == 2) {
tag = null;
} else if (pathElements.length == 3) {
tag = pathElements[2];
} else {
tag = null;
}
return StreamBuilder<List<ArtikelData>>(
stream: DatabaseService(tag: tag).artiklarByDate,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
return GlobalScaffold(
body: SingleChildScrollView(
child: Container(
child: Center(
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20, vertical: 15),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
GradientHeading(text: "Artiklar", large: true),
isAdmin
? NormalButton(
text: "Skapa ny artikel",
onPressed: () {
Navigator.pushNamed(
context, createNewArtikelRoute);
},
)
: Container(),
SizedBox(height: 10),
SingleChildScrollView(
controller: _scrollController,
scrollDirection: Axis.horizontal,
child: TagList(path: tag),
),
SizedBox(height: 10),
LatestArtiklar(
snapshot: snapshot,
totalPosts: snapshot.data.length,
numberOfPosts: 10,
),
],
),
),
),
),
),
);
} else if (!snapshot.hasData) {
return GlobalScaffold(
body: SingleChildScrollView(
child: Container(
child: Center(
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20, vertical: 15),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
GradientHeading(text: "Artiklar", large: true),
SizedBox(height: 10),
SingleChildScrollView(
scrollDirection: Axis.horizontal,
child: TagList(path: tag),
),
SizedBox(height: 10),
LatestArtiklar(hasNoPosts: true)
],
),
),
),
),
),
);
} else {
return GlobalScaffold(
body: Center(child: CircularProgressIndicator()),
);
}
},
);
}
}

Answer 1

That's because that widget is already built on the tree and thus, initState won't be called again for that widget.
You can override the didUpdateWidget method that will trigger each time that widget is rebuilt and make it jump on there, for example.
#override
void didUpdateWidget(Widget old){
super.didUpdateWidget(old);
_scrollController.jumpTo(initialOffset);
}

Answer 2

keepScrollOffset: false
If this property is set to false, the scroll offset is never saved and initialScrollOffset is always used to initialize the scroll offset.