Floating Button Behaviour

[clragon]

The scroll to top button currently appears at a fixed scroll off-set.

I would be very interested in a behaviour similar to the SliverAppBar with floating: true,
where the button would only appear if the user is scrolling up.

(I also hope I am not too annoying with all the requests)

[NamanShergill]

Hmm, how do you think that should be implemented? Would a gesture detector detecting a scroll up be enough?

[NamanShergill]

(I also hope I am not too annoying with all the requests)

No please, any feature requests to improve the library are welcome!

[clragon]

Would a gesture detector detecting a scroll up be enough?

Probably? I tried looking at how the slivers do it in the source code, but its convoluted, so I didnt figure it out.

[NamanShergill]

@clragon can you check out #8 if that is the implementation you are looking for?

[clragon]

oh yeah this is brilliant.

I was thinking it might even be nice to have a small off-set that the user has to scroll up before it shows up,
(which could be configured, like the promptScrollOffset)
but that might complicate the implementation alot.

[NamanShergill]

oh yeah this is brilliant.

I was thinking it might even be nice to have a small off-set that the user has to scroll up before it shows up, (which could be configured, like the promptScrollOffset) but that might complicate the implementation alot.

yeah, it will be hard to account for all the edge cases. I will release this implementation for now and update it later if I can think of a consistent way to implement that

[clragon]

maybe something like tracking the point at which the user first started scrolling up (when the scroll notification gets triggered) and whenever the user scrolls we compare it to the offset.
when a down-scrolling notification occurs, we simply set the point of first scrolling up to null again.

[NamanShergill]

@clragon Added in the PR, is that what you required?

Also I am having trouble with the parameter names being clear with their purpose so if you think they should be renamed to something else please let me know

[clragon]

this works wonderfully!
I dont think I can come up with any better names.

Though I think the doc string for scrollOffsetUntilVisible is incorrect?

If alwaysVisibleAtOffset is true, what offset should the user scroll in the opposite direction (ex, upwards scroll on a non-reversed vertical ScrollView) before the prompt becomes visible.

doesnt this only trigger when alwaysVisibleAtOffset is false?

[NamanShergill]

Right, I'll fix that

[clragon]

it also seems that the button will not show up in a NestedScrollView, if alwaysVisibleAtOffset is false,
and a scrollcontroller is passed to both the NestedScrollView and the ScrollWrapper.

I assume thats because of how the NestedScrollView works.

[NamanShergill]

it also seems that the button will not show up in a NestedScrollView, if alwaysVisibleAtOffset is false, and a scrollcontroller is passed to both the NestedScrollView and the ScrollWrapper.

I assume thats because of how the NestedScrollView works.

It's working fine for me, did you add NestedScrollView.sliverOverlapAbsorberHandleFor(context); to handle the overlap between the header and body, in a builder function inside the body? It's possible that it is showing up but is hidden behind the header due to the overlap.

Example:

flutter_scroll_to_top/example/lib/pages/nested_scroll_view_example.dart

Line 27 in d606041

NestedScrollView.sliverOverlapAbsorberHandleFor(context);

[NamanShergill]

Ah, wait.

The issue here is you are not supposed to pass a scroll controller in that case @clragon
That is how it works with ScrollViews inside the body of NestedScrollView, they are supposed to use the PrimaryScrollController

[clragon]

ah, I see. Yeah, I kind of suspected that.

[NamanShergill]

If you pass a scroll controller to a CustomScrollView without using the ScrollWrapper you will face a similar issue, where the CustomScrollView will start scrolling free from the NestedScrollView

[NamanShergill]

I will add a warning in the readme for this

[NamanShergill]

The new version is up on pub.dev

[clragon]

very nice 👌