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cc/ @LongCatIsLooong and @justinmc We recently updated the cupertino activity indicator in #58392. Is this different from the one that landed two weeks ago?

It looks like this will update us to the iOS 14 appearance, where the previous PR gave us some features that were missing from the iOS 13 version. No wasted work though, as it appears that the iOS 14 version is very similar to our now fully functional iOS 13 version. See #60047. CC @edwardaux

@ctrysbita Quickly checking out your branch and using the Flutter gallery pull-to-refresh demo, I still see the 12 pointed refresh indicator instead of the new 8 pointed one. Let me know if I'm doing something wrong or what the plan is for implementing the refresh indicator as seen in #60047.

// Copyright 2019 The Flutter team. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:math' show Random;

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CupertinoApp(
      title: 'Cupertino App',
      home: CupertinoRefreshControlDemo(),
    );
  }
}

class CupertinoRefreshControlDemo extends StatefulWidget {
  const CupertinoRefreshControlDemo();

  @override
  _CupertinoRefreshControlDemoState createState() =>
      _CupertinoRefreshControlDemoState();
}

class _CupertinoRefreshControlDemoState
    extends State<CupertinoRefreshControlDemo> {
  static const listCount = 20;
  var randomList = List<int>.generate(listCount, (i) => i + 1);

  void _shuffleList() => randomList.shuffle(Random());

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      child: CustomScrollView(
        // If left unspecified, the [CustomScrollView] appends an
        // [AlwaysScrollableScrollPhysics]. Behind the scene, the ScrollableState
        // will attach that [AlwaysScrollableScrollPhysics] to the output of
        // [ScrollConfiguration.of] which will be a [ClampingScrollPhysics]
        // on Android.
        // To demonstrate the iOS behavior in this demo and to ensure that the list
        // always scrolls, we specifically use a [BouncingScrollPhysics] combined
        // with a [AlwaysScrollableScrollPhysics]
        physics: const BouncingScrollPhysics(
          parent: AlwaysScrollableScrollPhysics(),
        ),
        slivers: [
          CupertinoSliverNavigationBar(
            automaticallyImplyLeading: false,
            largeTitle: Text(
              'Title',
            ),
          ),
          CupertinoSliverRefreshControl(
            onRefresh: () {
              return Future<void>.delayed(const Duration(seconds: 1))
                ..then<void>((_) {
                  if (mounted) {
                    setState(() => _shuffleList());
                  }
                });
            },
          ),
          SliverList(
            delegate: SliverChildBuilderDelegate(
              (context, index) {
                final title = 'Ok! $index';
                return Card(child: Text(title));
              },
              childCount: listCount,
            ),
          ),
        ],
      ),
    );
  }
}

@ctrysbita we have a policy that widget libraries should follow the latest OEM behavior, I think that policy justifies changing the current default appearance of the activity indicator when iOS 14 is out of beta.
I'm a little bit concerned that in 2 months the new flag introduced in the PR will have to be deprecated. Maybe we should wait until the official release of iOS 14 and then just change the appearance of the activity indicator without the flag?

Maybe we should wait until the official release of iOS 14 and then just change the appearance of the activity indicator without the flag?

If you do this, most applications will not be updated/installed in time for the release. Then all flutter applications will lag behind the native counterparts

When I was working on iOS 13 features in advance of the release, I just merged them early and no one seemed to have a problem with it. I vote for just removing the flag if no one sees a specific problem.

When I was working on iOS 13 features in advance of the release, I just merged them early and no one seemed to have a problem with it. I vote for just removing the flag if no one sees a specific problem.

However, iOS 14 is not officially released yet. Maybe we can use an enum to define the style.

It looks like this will update us to the iOS 14 appearance, where the previous PR gave us some features that were missing from the iOS 13 version. No wasted work though, as it appears that the iOS 14 version is very similar to our now fully functional iOS 13 version. See #60047. CC @edwardaux

@ctrysbita Quickly checking out your branch and using the Flutter gallery pull-to-refresh demo, I still see the 12 pointed refresh indicator instead of the new 8 pointed one. Let me know if I'm doing something wrong or what the plan is for implementing the refresh indicator as seen in #60047.

Here's my full code slightly modified from the gallery demo:

@justinmc The CupertinoSliverRefreshControl uses a builder to build refresh indicator. The default builder was set to build the default CupertinoActivityIndicator, which is still under iOS13 style.
Currently you have to implement a custom builder if you want to build the activity indicator with iOS14 style inside CupertinoSliverRefreshControl.

Thanks, I was able to see the new indicator by using the builder parameter and setting the style parameter to iOS 14 👍

Changes were rebased onto the latest master branch.

@ctrysbita Can you paste some code for how to test this widget? I'm having trouble using CupertinoSliverRefreshControl.

Otherwise I think this PR is pretty much good! Thanks for making those changes.

@ctrysbita Can you paste some code for how to test this widget? I'm having trouble using CupertinoSliverRefreshControl.

Otherwise I think this PR is pretty much good! Thanks for making those changes.

Actually you can build an activity indicator directly without CupertinoSliverRefreshControl.

import 'package:flutter/cupertino.dart';

main(List<String> args) {
  runApp(CupertinoApp(
    home: CupertinoPageScaffold(
      child: Center(
        child: CupertinoActivityIndicator(
          iOSVersionStyle: CupertinoActivityIndicatorIOSVersionStyle.iOS14,
          radius: 20,
        ),
      ),
    ),
  ));
}

Example code if you want to test it with CupertinoSliverRefreshControl

CupertinoSliverRefreshControl(
  onRefresh: () {
    return Future<void>.delayed(const Duration(seconds: 1))
      ..then<void>((_) {
        if (mounted) {
          setState(() => _shuffleList());
        }
      });
  },
  builder: (
    BuildContext context,
    RefreshIndicatorMode refreshState,
    double pulledExtent,
    double refreshTriggerPullDistance,
    double refreshIndicatorExtent,
  ) {
    final double percentageComplete =
        pulledExtent / refreshTriggerPullDistance;

    return Center(
      child: Stack(
        overflow: Overflow.visible,
        children: <Widget>[
          Positioned(
            top: 16,
            left: 0.0,
            right: 0.0,
            child: _buildIndicatorForRefreshState(
                refreshState, 14, percentageComplete),
          ),
        ],
      ),
    );
  },
),

Widget _buildIndicatorForRefreshState(RefreshIndicatorMode refreshState,
    double radius, double percentageComplete) {
  switch (refreshState) {
    case RefreshIndicatorMode.drag:
      // While we're dragging, we draw individual ticks of the spinner while simultaneously
      // easing the opacity in. Note that the opacity curve values here were derived using
      // Xcode through inspecting a native app running on iOS 13.5.
      const Curve opacityCurve = Interval(0.0, 0.35, curve: Curves.easeInOut);
      return Opacity(
        opacity: opacityCurve.transform(percentageComplete),
        child: CupertinoActivityIndicator.partiallyRevealed(
          radius: radius,
          progress: percentageComplete,
          iOSVersionStyle: CupertinoActivityIndicatorIOSVersionStyle.iOS14,
        ),
      );
    case RefreshIndicatorMode.armed:
    case RefreshIndicatorMode.refresh:
      // Once we're armed or performing the refresh, we just show the normal spinner.
      return CupertinoActivityIndicator(
        radius: radius,
        iOSVersionStyle: CupertinoActivityIndicatorIOSVersionStyle.iOS14,
      );
    case RefreshIndicatorMode.done:
      // When the user lets go, the standard transition is to shrink the spinner.
      return CupertinoActivityIndicator(
        radius: radius * percentageComplete,
        iOSVersionStyle: CupertinoActivityIndicatorIOSVersionStyle.iOS14,
      );
    default:
      // Anything else doesn't show anything.
      return Container();
  }
}

Deprecation follow up at #62521.