Add `CupertinoLinearActivityIndicator` by ValentinVignal · Pull Request #170108 · flutter/flutter

ValentinVignal · 2025-06-06T03:15:09Z

Fixes #156167

Continuation of #156287

Native version:

Following team discussions, we've decided to adopt the stadium shape:

#170108 (comment)
#170108 (comment)

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

victorsanni

Thanks for this PR. Can you attach images comparing to native as well as a description of the native APIs for similar behaviors? For a design review.

packages/flutter/lib/src/cupertino/activity_indicator.dart

packages/flutter/test/cupertino/activity_indicator_test.dart

victorsanni · 2025-06-11T21:54:44Z

packages/flutter/lib/src/cupertino/activity_indicator.dart

+  @override
+  void paint(Canvas canvas, Size size) {
+    // Draw the background of the progress bar.
+    canvas.drawRRect(


I'm wondering if the native version is a rounded rect or a rounded superellipse (squircle). Can you attach images to the PR description comparing the native version?

I've tried to look at https://developer.apple.com/design/human-interface-guidelines/progress-indicators

and from the photo

it looks like rounded rect? But again, I half guessing here

The native photo attached has less-rounded corners on the edges than the flutter photo attached. But the actual blue line has the same rounding (I think) in both.

It's true on the picture it looks like the container has less rounded corners.

However, if I look at https://developer.apple.com/design/human-interface-guidelines/progress-indicators

it looks like the background AND the blue line are having a stadium shape, which is like the current implementation

Having said that, what would you prefer me to do?

I can replace the current native image attached to the PR description with the ones from https://developer.apple.com/design/human-interface-guidelines/progress-indicators

Can you attach images from a running native iOS app? The goal is to match live widgets, not HIG website photos.

Fair enough, I create a straightforward macOS app:

It looks like a stadium shape to me. What do you think?

Sounds good. If the native app is stadium-shaped then it should be stadium-shaped.

ValentinVignal · 2025-06-12T09:00:38Z

@victorsanni I have attached the picture from the issue in the description.

I might need a bit of assistance to provide what you need from me, as I'm not very familiar with Cupertino and Apple specs/environment. For context, I saw the issue #156167 and noticed that the PR to fix it #156287 was closed due to a lack of tests. So, I've added those tests.

I'm not saying I'm unwilling to apply your suggestion; I just need you to be extra explicit because I might not fully understand everything.

packages/flutter/lib/src/cupertino/activity_indicator.dart

ValentinVignal · 2025-06-14T11:44:58Z

Thank you for the feedbacks. I improved the documentation in Improve documentation

victorsanni

LGTM pending reviews from others.

victorsanni

Hi @ValentinVignal,

Looking through this again I realized there is already a Material widget with similar behavior: LinearProgressIndicator. Is there an opportunity here to share logic already in that widget?

ValentinVignal · 2025-07-01T02:11:50Z

@victorsanni, looking at LinearProgressIndicator, I think we could try to reuse the _LinearProgressIndicatorPainter.
I can try to

Move _LinearProgressIndicatorPainter to progress_indicator.dart and rename it to LinearProgressIndicatorPainter
Reuse it in CupertinoLinearActivityIndicator

What do you think?

MitchellGoodwin · 2025-07-01T17:05:28Z

Imo, we could move the majority of ProgressIndicator down as well. The only hiccup is _getValueColor that I can see. Two options for that are:

Create a RawProgressIndicator in Widgets. Have it implement everything but _getValueColor. ProgressIndicator in Material extends off of RawProgressIndicator and adds _getValueColor. The Cupertino version uses RawProgressIndicator.
Move ProgressIndicator down entirely, and make _getValueColor public. Have the Widgets version default to logic that doesn't use themes. Create a MaterialProgressIndicator that overrides getValueColor to the current Material defaults. Cupertino extends off of ProgressIndicator.

I personally like option 2 a bit better. Important to point out that this PR uses "progress" where Material uses "value". We don't want that API drift.

For the painter, moving that down sounds like a good idea to me as well, but it looks like it needs to have generic, or possibly empty curve defaults.

victorsanni · 2025-07-01T19:35:33Z

Create a MaterialProgressIndicator that overrides getValueColor to the current Material defaults.

Why can't LinearProgressIndicator and CircularProgressIndicator override getValueColor directly?

MitchellGoodwin · 2025-07-01T19:43:30Z

Why can't LinearProgressIndicator and CircularProgressIndicator override getValueColor directly?

That's valid too, they just would both override to the same value it looks like. But overriding getValueColor twice would be less code than making a new class so that's probably better.

victorsanni · 2025-07-01T19:46:32Z

Right now ProgressIndicator is just an accessibility wrapper. Can we move more logic from LinearProgressIndicator and CircularProgressIndicator into ProgressIndicator?

victorsanni · 2025-07-10T18:43:40Z

make _getValueColor public.

And protected too.

dkwingsmt · 2025-07-30T18:21:42Z

Hi! @ValentinVignal Are you able to address the comments above so we can work together to get this landed? This is a great addition and I'm looking forward to it!

ValentinVignal · 2025-07-31T06:27:17Z

@dkwingsmt yes I'd be happy to resume it. However, @victorsanni asked a question to @MitchellGoodwin here. Or it was a bit unclear to me everyone agreed on the solution

victorsanni · 2025-08-06T18:34:24Z

Hey @ValentinVignal, feel free to go ahead with implementing option 2 in #170108 (comment). Basically we want to share as much code as possible between material and cupertino.

ValentinVignal · 2025-08-15T16:38:43Z

@victorsanni @MitchellGoodwin I did my best, and I created ProgressIndicator.

As you mentioned, Cupertino uses progress and Material value, which brings a bit of an issue to share variables and code.
MaterialProgressIndicator has a nullable value. Null means the progress indicator is indeterminate and animated. But that's not the case for CupertinoActivityIndicator. progress is non-nullable and defaulted to 1.0. Another variable bool animating indicates whether or not the widget is animated.
1. Because of that, I had to create this getter animating in ProgressIndicatorMixin which I'm not very happy with.
2. The documentation of widget's ProgressIndicator currently mention that value being null means the indicator is indeterminate and animated. But that's not true for Cupertino
The current implementation lost the

ValentinVignal · 2025-08-15T16:39:53Z

packages/flutter/lib/src/widgets/progress_indicator.dart

+  /// If null, this progress indicator is indeterminate, which means the
+  /// indicator displays a predetermined animation that does not indicate how
+  /// much actual progress is being made.
+  final double? value;


This part is not true for Cupertino

Sorry to belabor this, but can you explain why this is not true for cupertino again?

value is never null for CupertinoActivityIndicator.

For the animated/indeterminate version, value = 1. This value is used to calculate the number of "ticks" to display:

Here is a video, which I think makes it clearer:

Screen.Recording.2025-08-23.at.1.53.27.PM.mov

IMO I think this is fine as long as the cupertino indicators call out that they are never null.

packages/flutter/lib/src/cupertino/activity_indicator.dart

…rivate

…cator

dkwingsmt · 2025-09-17T18:41:31Z

Is it ready for another round of review? (from triage)

ValentinVignal · 2025-09-18T03:08:14Z

@dkwingsmt yes it is read to get another round of review :)

@victorsanni also had an open question here : #170108 (comment)

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Fixes flutter#156167 Continuation of flutter#156287 <img width="712" alt="Screenshot 2025-06-06 at 10 00 32 AM" src="proxy.php?url=https://github.com/user-attachments/assets/d878287f-8236-4acf-80a5-6ecb6d2a09ec" /> Native version: ![image](https://github.com/user-attachments/assets/bb28cd01-c7be-481b-bb22-834b65dd35f5) --- Following team discussions, we've decided to adopt the stadium shape: flutter#170108 (comment) flutter#170108 (comment) ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord].  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

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ValentinVignal added 9 commits September 12, 2025 20:42

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