public class MainActivity extends Activity {

     private HealthTrackingService healthTrackingService = null;
     private HealthTracker ecgTracker = null;

     private final ConnectionListener connectionListener = new ConnectionListener() {
         @Override
         public void onConnectionSuccess() {
             // Connection with Health Platform succeeded. Check capability.
             List<HealthTrackerType> availableTrackers = healthTrackingService.getTrackingCapability().getSupportHealthTrackerTypes();
             if (!availableTrackers.contains(HealthTrackerType.ECG_ON_DEMAND)) {
                 // Tracking Electrocardiogram (ECG) On-Demand is not available.
                 // Display a proper message to the user. 
             } else {
                 ecgTracker = healthTrackingService.getHealthTracker(HealthTrackerType.ECG_ON_DEMAND);
             }
         }

         @Override
         public void onConnectionEnded() {
             // The connection with Health Platform was ended.
         }

         @Override
         public void onConnectionFailed(HealthTrackerException exception) {
             //Check the error code and resolve it.
             if (exception.hasResolution()) {
                 // Display a proper message before calling resolve().
                 exception.resolve(MainActivity.this); // Jumping to an application market to install or update Health Platform.
             } else {
                 // Display a proper message for the exception.
             }
         }
     }

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         // Check and request permission.
         if (ActivityCompat.checkSelfPermission(getApplicationContext(), "android.permission.BODY_SENSORS")
                 == PackageManager.PERMISSION_DENIED) {
             requestPermissions(this, new String[]{Manifest.permission.BODY_SENSORS}, 0);
         }

         try {
             // Connect the Health Tracking Service.
             healthTrackingService = new HealthTrackingService(connectionListener, context);
             healthTrackingService.connectService();
         } catch (Throwable t) {
             // Exception handling.
         }
     }
 }