initStepCountObserver.md

initStepCountObserver

DEPRECATED - This method has been depreacted in favor of background initializers and will be removed in the next major release. See the background page for more information.

Setup an HKObserverQuery for step count (HKQuantityTypeIdentifierStepCount) that will trigger an event listenable on react-native NativeAppEventEmitter when the Healthkit step count has changed.

The initStepCountObserver method must be called before adding a listener to NativeAppEventEmitter. After the step count observer has been initialized you can listen to the NativeAppEventEmitter change:steps event and re-fetch relevent step count data in the event handler.

The initStepCountObserver method should be called after Healthkit has been successfully initialized (AppleHealthKit.initHealthKit has been called without error).

// import NativeAppEventEmitter from react-native
import { Navigator, View, NativeAppEventEmitter } from 'react-native'

Call the method:

AppleHealthKit.initHealthKit(HKOPTIONS, (err, res) => {
  if (this._handleHKError(err, 'initHealthKit')) {
    return;
  }

  // initialize the step count observer
  AppleHealthKit.initStepCountObserver({}, () => {});

  // add event listener for 'change:steps' and handle the
  // event in the event handler function.
  //
  // when adding a listener, a 'subscription' object is
  // returned that must be used to remove the listener
  // when the component unmounts. The subscription object
  // must be accessible to any function/method/instance
  // that will be unsubscribing from the event.
  this.sub = NativeAppEventEmitter.addListener(
    'change:steps',
    (evt) => {
      // a 'change:steps' event has been received. step
      // count data should be re-fetched from Healthkit.
      this._fetchStepCountData();
    }
  );

  // other tasks to perform after Healthkit has been
  // initialized (fetch relevant Healthkit data).
  this._fetchStepCountData();
  this._fetchOtherRelevantHealthkitData();
  // ...
});

...

// when the component where the listener was added unmounts
// (or whenever the listener should be removed), call the
// 'remove' method of the subscription object.
componentWillUnmount() {
  this.sub.remove();
}

Note - Some data types, such as step counts, have a minimum frequency of HKUpdateFrequencyHourly. This frequency is enforced transparently.

DEPRECATED - This method has been depreacted in favor of background initializers and will be removed in the next major release. See the background page for more information.