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

// Copyright 2014 The Flutter Authors. 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' as math;

import 'package:flutter/widgets.dart';

import 'colors.dart';

const double _kDefaultIndicatorRadius = 10.0;

// Extracted from iOS 13.2 Beta.
const Color _kActiveTickColor = CupertinoDynamicColor.withBrightness(
  color: Color(0xFF3C3C44),
  darkColor: Color(0xFFEBEBF5),
);

/// An iOS-style activity indicator that spins clockwise.
///
/// {@youtube 560 315 https://www.youtube.com/watch?v=AENVH-ZqKDQ}
///
/// {@tool dartpad}
/// This example shows how [CupertinoActivityIndicator] can be customized.
///
/// ** See code in examples/api/lib/cupertino/activity_indicator/cupertino_activity_indicator.0.dart **
/// {@end-tool}
///
/// See also:
///
///  * <https://developer.apple.com/ios/human-interface-guidelines/controls/progress-indicators/#activity-indicators>
class CupertinoActivityIndicator extends StatefulWidget {
  /// Creates an iOS-style activity indicator that spins clockwise.
  const CupertinoActivityIndicator({
    super.key,
    this.color,
    this.animating = true,
    this.radius = _kDefaultIndicatorRadius,
  })  : assert(animating != null),
        assert(radius != null),
        assert(radius > 0.0),
        progress = 1.0;

  /// Creates a non-animated iOS-style activity indicator that displays
  /// a partial count of ticks based on the value of [progress].
  ///
  /// When provided, the value of [progress] must be between 0.0 (zero ticks
  /// will be shown) and 1.0 (all ticks will be shown) inclusive. Defaults
  /// to 1.0.
  const CupertinoActivityIndicator.partiallyRevealed({
    super.key,
    this.color,
    this.radius = _kDefaultIndicatorRadius,
    this.progress = 1.0,
  })  : assert(radius != null),
        assert(radius > 0.0),
        assert(progress != null),
        assert(progress >= 0.0),
        assert(progress <= 1.0),
        animating = false;

  /// Color of the activity indicator.
  ///
  /// Defaults to color extracted from native iOS.
  final Color? color;

  /// Whether the activity indicator is running its animation.
  ///
  /// Defaults to true.
  final bool animating;

  /// Radius of the spinner widget.
  ///
  /// Defaults to 10px. Must be positive and cannot be null.
  final double radius;

  /// Determines the percentage of spinner ticks that will be shown. Typical usage would
  /// display all ticks, however, this allows for more fine-grained control such as
  /// during pull-to-refresh when the drag-down action shows one tick at a time as
  /// the user continues to drag down.
  ///
  /// Defaults to 1.0. Must be between 0.0 and 1.0 inclusive, and cannot be null.
  final double progress;

  @override
  State<CupertinoActivityIndicator> createState() => _CupertinoActivityIndicatorState();
}

class _CupertinoActivityIndicatorState extends State<CupertinoActivityIndicator>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 1),
      vsync: this,
    );

    if (widget.animating) {
      _controller.repeat();
    }
  }

  @override
  void didUpdateWidget(CupertinoActivityIndicator oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.animating != oldWidget.animating) {
      if (widget.animating) {
        _controller.repeat();
      } else {
        _controller.stop();
      }
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: widget.radius * 2,
      width: widget.radius * 2,
      child: CustomPaint(
        painter: _CupertinoActivityIndicatorPainter(
          position: _controller,
          activeColor: widget.color ?? CupertinoDynamicColor.resolve(_kActiveTickColor, context),
          radius: widget.radius,
          progress: widget.progress,
        ),
      ),
    );
  }
}

const double _kTwoPI = math.pi * 2.0;

/// Alpha values extracted from the native component (for both dark and light mode) to
/// draw the spinning ticks.
const List<int> _kAlphaValues = <int>[
  47,
  47,
  47,
  47,
  72,
  97,
  122,
  147,
];

/// The alpha value that is used to draw the partially revealed ticks.
const int _partiallyRevealedAlpha = 147;

class _CupertinoActivityIndicatorPainter extends CustomPainter {
  _CupertinoActivityIndicatorPainter({
    required this.position,
    required this.activeColor,
    required this.radius,
    required this.progress,
  })  : tickFundamentalRRect = RRect.fromLTRBXY(
          -radius / _kDefaultIndicatorRadius,
          -radius / 3.0,
          radius / _kDefaultIndicatorRadius,
          -radius,
          radius / _kDefaultIndicatorRadius,
          radius / _kDefaultIndicatorRadius,
        ),
        super(repaint: position);

  final Animation<double> position;
  final Color activeColor;
  final double radius;
  final double progress;

  final RRect tickFundamentalRRect;

  @override
  void paint(Canvas canvas, Size size) {
    final Paint paint = Paint();
    final int tickCount = _kAlphaValues.length;

    canvas.save();
    canvas.translate(size.width / 2.0, size.height / 2.0);

    final int activeTick = (tickCount * position.value).floor();

    for (int i = 0; i < tickCount * progress; ++i) {
      final int t = (i - activeTick) % tickCount;
      paint.color = activeColor
          .withAlpha(progress < 1 ? _partiallyRevealedAlpha : _kAlphaValues[t]);
      canvas.drawRRect(tickFundamentalRRect, paint);
      canvas.rotate(_kTwoPI / tickCount);
    }

    canvas.restore();
  }

  @override
  bool shouldRepaint(_CupertinoActivityIndicatorPainter oldPainter) {
    return oldPainter.position != position ||
        oldPainter.activeColor != activeColor ||
        oldPainter.progress != progress;
  }
}