tutorials | galaxy watch, health

Workout, a Tizen Sample App: Calculating Distance Traveled

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Patryk Falba

Senior Software Engineer

This is the second blog in a series to introduce the sample application Workout, a Tizen example for monitoring health sensors on a wearable device.

The previous blog, Workout -- A Tizen Sample App for Monitoring Health Sensors, introduced the sample application, Workout, for runners who own a wearable device. In this blog, I will describe how one of the key features, traveled distance, is calculated.

Distance

Implementation

To calculate the traveled distance, the application uses the LocationService class providing location-related GPS data. This service uses the Tizen.Location API to initialize the GPS receiver:

Services/LocationService.cs

/// <summary>
/// Initializes LocationService class instance.
/// </summary>
private LocationService()
{
    _locator = new Locator(LocationType.Hybrid)
    {
        Interval = _gpsCallbackInterval
    };
 
    AttachEvents();
}

The API is also used to set the change handlers:

Services/LocationService.cs

/// <summary>
/// Sets service listeners.
/// </summary>
private void AttachEvents()
{
    _locator.ServiceStateChanged += (sender, args) => ServiceStateChanged?.Invoke(this, args.ServiceState);
    _locator.LocationChanged += (sender, args) => LocationChanged?.Invoke(this, args.Location);
    _locator.SettingChanged += (sender, args) => SettingChanged?.Invoke(this, args.IsEnabled);
}

Every time the location changes, the LocationChanged event is invoked with the new location.

This event has an attached listener in LocationModel which receives the new location object. The new location is used to calculate the distance to the previous location and stored in a _locationData object:

Models/LocationModel.cs

_locationData.Distance += location.GetDistanceTo(_lastLocation) / SettingsService.Instance.Distance.UnitToKmRatio;

The new location data is passed to MainModel, where all workout data are gathered and processed before being sent to viewModels.

The entire flow of location data and other workout data is described in detail at tizenschool.org

In the next blog in this series, I will discuss how data is gathered from the heart rate monitor.