Detect if a SingleChildScrollview/Listview can be scrolled - flutter

Question

So, i have a widget with infinite width (Row) . To fill the widget with items i'm using a Lisview builder with Axis horizontal. I also can use a SingleChildScrollview with axis horizontal and a Row as the child.
If there is a few items, the width of the screen is not filled, so that's great. However, when there is a lot of items, the Listview becomes "scrollable" , and i can scroll to the right to reveal the items.
I would like to know if the list is scrollable (if it overflows). The purpose is to show a little text saying "Scroll to reveal more>>".
I know i can use maths and calculate the items width with the screen width. However... The Listview already knows this, so i was wondering if there was a way of getting access to that information

Answer 1

I had a similar problem. I found this solution here: Determine Scroll Widget height
Here's my question in case it's helpful: How do you tell if scrolling is not needed in a SingleChildScrollView when the screen is first built?
Solution:
Import the scheduler Flutter library:
import 'package:flutter/scheduler.dart';
Create a boolean flag inside the state object but outside of the build method to track whether build has been called yet:
bool buildCalledYet = false;
Create a boolean isScrollable variable inside the state object but outside of the build method:
bool isScrollable;
Add the following in the beginning of the build method:
if (!firstBuild) {
firstBuild = true;
SchedulerBinding.instance.addPostFrameCallback((_) {
setState(() {
isScrollable = !(_scrollController.position.maxScrollExtent > 0);
});
});
}
(The purpose of buildCalledYet is to prevent this code from causing build to be called over and over again.)
If isScrollable is true, then show your text.

Answer 2

I created a widget called ScrollCheckerWidget with a controller property to pass the controller of a scrollable widget and check if it is scrollable in the view. The ScrollCheckerWidget widget has a builder callback function where you can return a widget and use the isScrollable boolean from the builder to check if the widget related to the controller is scrollable or not. Here you have the code:
import 'package:flutter/material.dart';
class ScrollCheckerWidget extends StatefulWidget {
const ScrollCheckerWidget({
Key? key,
required this.controller,
required this.builder,
}) : super(key: key);
final ScrollController controller;
final Widget Function(bool isScrollable) builder;
#override
State<EGScrollCheckerWidget> createState() => _EGScrollCheckerWidgetState();
}
class _EGScrollCheckerWidgetState extends State<EGScrollCheckerWidget> {
late final ScrollController _scrollController;
late bool _isScrollable;
#override
void initState() {
_scrollController = widget.controller;
_isScrollable = false;
WidgetsBinding.instance.addPostFrameCallback((_) {
setState(() {
_isScrollable = _scrollController.position.maxScrollExtent > 0;
});
});
super.initState();
}
#override
Widget build(BuildContext context) {
return widget.builder.call(_isScrollable);
}
}

Answer 3

In builder:
return NotificationListener(
onNotification: (scrollNotification) {
print("ScrollStartNotification");
// add your logic here
},
child: SingleChildScrollView(...
Am trying to detect exact same thing myself, wrapping SingleChildScrollView with NotificationListener at least gave me a point of reference to start working on this.