flutter_workoutkit

A Flutter plugin for Apple's WorkoutKit. Use it to build custom workouts in Dart, then preview, validate, export and schedule them for the Workout app on Apple Watch.

Requirements: iOS 17.0+ and an Apple Watch paired with the iPhone to actually run workouts. Pool swim goals and step names need iOS 18.0+. Android is not supported: the widgets render nothing and the API calls throw.

📦 Stability

1.0.0 is the first stable release; the API follows semantic versioning. Upgrading from 0.0.x? See the migration guide and the CHANGELOG. Please report issues and feature requests on GitHub.

🔑 Key Features

• Four workout types: custom interval workouts, single goal, pacer and swim-bike-run.
• Goals: distance, time, energy, open, and pool swim distance-within-time.
• Alerts: heart rate, cadence, power, speed and pace.
• Preview a workout in Apple's native sheet, from which the user adds it to their Watch, either from your own Flutter UI (WorkoutKit.presentPreview) or with a ready-made native button.
• Schedule workouts directly onto the Watch with WorkoutScheduler.
• Validate a workout against WorkoutKit's own rules before showing it, with structured issues (code and path) you can localize.
• Value semantics: all models support ==, hashCode and copyWith.
• Export and import workouts in WorkoutKit's binary format.

🎥 Preview

📸 Screenshots

📥 Installation

dependencies:
  flutter_workoutkit: ^1.0.0

Set your iOS deployment target to 17.0 or higher in Xcode (Runner target → Minimum Deployments). If your app still uses CocoaPods, set it in ios/Podfile too:

platform :ios, '17.0'

The plugin supports Swift Package Manager, which Flutter uses by default, and CocoaPods.

You don't need a HealthKit entitlement or HealthKit usage descriptions for previewing or scheduling. You only need them if you still call the deprecated WorkoutKit.requestHealthPermissions.

🚀 Quick start

import 'package:flutter_workoutkit/flutter_workoutkit.dart';

final tempoRun = CustomWorkout(
  activityType: WorkoutActivityType.running,
  location: WorkoutLocationType.outdoor,
  displayName: 'Tempo Run',
  warmup: WorkoutStep(
    goal: const WorkoutGoal.time(Duration(minutes: 10)),
    alert: HeartRateZoneAlert(zone: 2),
  ),
  blocks: [
    IntervalBlock(iterations: 3, steps: [
      IntervalStep(
        purpose: IntervalStepPurpose.work,
        goal: const WorkoutGoal.distance(2, WorkoutGoalUnit.kilometers),
        alert: PaceRangeAlert(
          fastestPace: const Duration(minutes: 5),
          slowestPace: const Duration(minutes: 5, seconds: 30),
        ),
      ),
      IntervalStep(
        purpose: IntervalStepPurpose.recovery,
        goal: const WorkoutGoal.time(Duration(seconds: 90),
            unit: WorkoutGoalUnit.seconds),
      ),
    ]),
  ],
  cooldown: WorkoutStep(goal: const WorkoutGoal.time(Duration(minutes: 5))),
);

// 1. Let the user preview the workout and add it to their Watch from any
//    Flutter button:
FilledButton(
  onPressed: () => WorkoutKit.presentPreview(tempoRun),
  child: const Text('Add to Apple Watch'),
);

// 2. Or use the ready-made native button:
WorkoutPreviewButton(workout: tempoRun);

// 3. Or schedule it directly:
if (await WorkoutScheduler.requestAuthorization() ==
    SchedulerAuthorizationState.authorized) {
  await WorkoutScheduler.schedule(tempoRun, DateTime(2026, 10, 12, 7, 0));
}

There are more workouts in lib/src/samples. The example app shows every feature: the native button and presentPreview, validation with structured issues, customizing a workout with copyWith, export/import and scheduling.

🏋️ Workouts

Class	Description
CustomWorkout	An optional warmup, then IntervalBlocks of work/recovery IntervalSteps repeated iterations times, then an optional cooldown.
SingleGoalWorkout	One goal for the whole workout. Swimming takes a swimmingLocation; every other activity takes a location.
PacerWorkout	Cover a distance in a target time.
SwimBikeRunWorkout	Ordered multisport legs (MultisportActivity).

Not every activity supports every workout type, goal or alert; for example, a pacer workout only supports a few activities. Check up front with WorkoutKit.validate.

Pool swimming: use a CustomWorkout with activityType: swimming and location: indoor. WorkoutKit does not accept pool swim goals in a SingleGoalWorkout.

🎯 Goals

Constructor	Available on
WorkoutGoal.open()	iOS 17
WorkoutGoal.distance(5, WorkoutGoalUnit.kilometers) (meters, kilometers, miles, yards)	iOS 17
WorkoutGoal.time(Duration(minutes: 30), unit: WorkoutGoalUnit.minutes)	iOS 17
WorkoutGoal.energy(400) (kilocalories by default)	iOS 17
WorkoutGoal.poolSwimDistanceWithTime(distance: 100, distanceUnit: WorkoutGoalUnit.meters, duration: Duration(minutes: 2))	iOS 18

Durations are sent exactly; unit only controls how the Watch displays them.

WorkoutGoalUnit.calories are small calories (1000 cal = 1 kcal). Most apps mean kilocalories.

🔔 Alerts

Alert	Notes
HeartRateZoneAlert(zone: 1–5)	Uses the zones configured in the Workout app.
HeartRateRangeAlert(lowerBound:, upperBound:)	Beats per minute.
CadenceRangeAlert / CadenceThresholdAlert	Steps or revolutions per minute.
PowerZoneAlert / PowerRangeAlert / PowerThresholdAlert	Watts. The average metric needs iOS 17.4+.
SpeedRangeAlert / SpeedThresholdAlert	m/s, km/h, mph or knots, using the current or average speed.
PaceRangeAlert(fastestPace:, slowestPace:) / PaceThresholdAlert(pace:)	Time per km or per mile.

WorkoutKit has no separate pace alert. Pace alerts are sent to the Watch as speed alerts, and the Watch shows them as pace. A workout read back from WorkoutKit (from the scheduler or importWorkout) therefore returns them as SpeedRangeAlert/SpeedThresholdAlert in m/s.

WorkoutStep(displayName: ...) names a step on the Watch on iOS 18+. On iOS 17 the name is ignored.

👀 Previewing workouts

Apple's preview sheet shows the workout and lets the user add it to the Workout app on their Apple Watch. There are two ways to open it.

From your own UI: WorkoutKit.presentPreview

FilledButton(
  onPressed: () async {
    try {
      await WorkoutKit.presentPreview(tempoRun); // completes when the sheet closes
    } on WorkoutkitException catch (e) {
      // UNSUPPORTED_WORKOUT, UNSUPPORTED_OS, ALREADY_PRESENTING, NO_PRESENTER,
      // or UNSUPPORTED_PLATFORM when not on iOS.
      debugPrint('${e.code}: ${e.message}');
    }
  },
  child: const Text('Add to Apple Watch'),
)

Use any widget, gesture or flow, for example right after the user saves a workout in your app. Only one preview can be open at a time.

Ready-made native button: WorkoutPreviewButton

WorkoutPreviewButton embeds a native button that opens the same sheet, with no extra code:

WorkoutPreviewButton(
  workout: tempoRun,
  buttonTitle: 'Add to Apple Watch',
  sfSymbol: 'applewatch',          // optional, no icon by default
  backgroundColor: Colors.black,
  foregroundColor: Colors.white,
  cornerRadiusSize: 10,
  buttonHeight: 54,
  fontSize: 16,
  fontWeight: FontWeight.w600,
  onError: (WorkoutkitException e) => debugPrint('${e.code}: ${e.message}'),
)

If the workout can't be built (for example, it's unsupported, or it uses a pool swim goal on iOS 17), the button renders empty and calls onError. Changing workout or any styling recreates the native view.

⌚ Scheduling to Apple Watch

if (!await WorkoutScheduler.isSupported()) return;

final state = await WorkoutScheduler.requestAuthorization(); // asks once
if (state != SchedulerAuthorizationState.authorized) return;

final scheduled = await WorkoutScheduler.schedule(tempoRun, DateTime(2026, 10, 12, 7, 0));
final all = await WorkoutScheduler.scheduledWorkouts();
await WorkoutScheduler.markComplete(scheduled);
await WorkoutScheduler.remove(scheduled);
await WorkoutScheduler.removeAll();
final max = await WorkoutScheduler.maxAllowedScheduledWorkoutCount();

Dates are local time with minute precision. Each scheduled workout has a plan id (a UUID). You can set your own id on any workout, or let WorkoutKit generate one.

✅ Validation

WorkoutKit crashes the app when it is given an unsupported combination, such as an activity a pacer workout doesn't support or a goal that isn't valid for the activity. The plugin runs WorkoutKit's supports… checks before building every workout and turns failures into errors. You can also run the checks yourself:

final result = await WorkoutKit.validate(workout);
if (!result.isValid) {
  for (final issue in result.details) {
    // e.g. unsupportedGoal at blocks[0].steps[1]
    print('${issue.code.name} at ${issue.path}: ${issue.message}');
  }
}

Each WorkoutValidationIssue has a code (unsupportedActivity, unsupportedGoal, unsupportedAlert, unsupportedActivityOrdering, missingBlocks, missingActivities, unsupportedOS or invalidWorkout) and a path into the workout, such as activityType, goal or blocks[0].steps[1]. Use them to show your own (localized) messages or to highlight the step that's wrong. result.issues holds the English messages.

The same issues are available on errors: WorkoutkitException.validationIssues.

🧩 Working with workouts

All models compare by value and can be copied with changes:

final longer = tempoRun.copyWith(
  displayName: 'Long Tempo Run',
  blocks: [tempoRun.blocks.first.copyWith(iterations: 5)],
);

longer == tempoRun;                                         // false
Workout.fromJson(tempoRun.toJson()) == tempoRun;            // true
{HeartRateZoneAlert(zone: 2), HeartRateZoneAlert(zone: 2)}; // a set of one

copyWith can't set a nullable field back to null; create a new object for that.

📦 Export / import

final Uint8List data = await WorkoutKit.exportWorkout(workout); // WorkoutKit's dataRepresentation
final Workout copy = await WorkoutKit.importWorkout(data);

⚠️ Error handling

Native failures are thrown as WorkoutkitException, which has a code, a message and, for some codes, details:

code	Meaning
INVALID_ARGUMENT	The workout JSON was malformed (a bug: please report it).
UNSUPPORTED_WORKOUT	WorkoutKit doesn't support this activity/goal/alert combination. See validationIssues.
UNSUPPORTED_OS	The feature needs a newer iOS version. See validationIssues.
NOT_FOUND	No scheduled workout matched the given id and date.
SERIALIZATION_ERROR	Export or import failed.
ALREADY_PRESENTING	presentPreview was called while a preview is open.
NO_PRESENTER	presentPreview found no visible screen to present from.
UNSUPPORTED_PLATFORM	Called on a platform other than iOS.
WATCH_NOT_PAIRED	WorkoutKit reported that no Apple Watch is paired.
WORKOUT_APP_NOT_INSTALLED	WorkoutKit reported that the Workout app isn't installed on the Watch.
UNKNOWN	Any other native error; see message.

🔁 Migrating from 0.0.x to 1.0.0

• iOS 17.0 is now the minimum. The podspec requires it, so CocoaPods rejects apps that target an older version. Previously the button crashed on iOS 16.
• The entry point is now WorkoutKit. Workoutkit still works: it's an alias, not deprecated.
• HealthKit is no longer required. WorkoutKit.requestHealthPermissions and hasHealthPermissions are deprecated. Use WorkoutScheduler.requestAuthorization instead, and remove the HealthKit capability if nothing else in your app uses it.
• IntervalBlock.type is deprecated and optional. WorkoutKit never used it; set IntervalStep.purpose instead.
• WorkoutAlert is now abstract. WorkoutAlert.fromJson returns the concrete subclass.
• WorkoutService was removed. It called a native method that never existed.
• WorkoutActivityType.dance is deprecated. Use cardioDance or socialDance.
• toJson() omits null fields.
• sampleSingleGoalEnergyWorkout now uses 500 kilocalories instead of 1000 small calories.
• The WorkoutPreviewButton no longer shows the Apple logo by default. Pass sfSymbol to show an icon.
• The PaceRangeAlert/PaceThresholdAlert API changed. It was never exported before.

🧪 Development

See CONTRIBUTING.md. Running just check runs the analyzer, the Dart tests and the Swift tests.

🚧 Roadmap

• ✅ WorkoutPreviewButton for previewing workouts, with customization
• ✅ WorkoutKit.presentPreview to open the preview from any Flutter UI
• ✅ Structured validation issues
• ✅ Value equality and copyWith on all models
• ✅ WorkoutScheduler and scheduled workout plans
• ✅ poolSwimDistanceWithTime goals
• ✅ Pace alerts
• ✅ Validation, export and import
• ✅ Graceful errors instead of native crashes
• ✅ Tests (Dart, Swift and integration)
• ✅ Swift Package Manager support (CocoaPods still works)
• ❌ macOS support (WorkoutKit's scheduler and preview exist on macOS 15)
• ❌ (Long term) Explore options for supporting Android

📝 License

This project is licensed under the Apache License 2.0. See the LICENSE file for details.

📧 Contact

For questions or feedback, please contact me at a@adamkramer.dev

💰 Buy me a coffee

If you find this plugin useful, please consider buying me a coffee: