Replace getMostProbableActivity with sorted getter.

Author: ghengeveld

README.md

@@ -88,11 +88,12 @@ import ActivityRecognition from 'react-native-activity-recognition'
 ...
 
 // Start activity detection
-ActivityRecognition.start(1000) // detection interval in ms
+const detectionIntervalMillis = 1000
+ActivityRecognition.start(detectionIntervalMillis)
 
 // Subscribe to updates
 this.unsubscribe = ActivityRecognition.subscribe(detectedActivities => {
-  const mostProbable = ActivityRecognition.getMostProbableActivity(detectedActivities) // => { type: 'STILL', confidence: 77 }
+  const mostProbableActivity = detectedActivities.sorted[0]
 })
 
 ...
@@ -102,7 +103,7 @@ ActivityRecognition.stop()
 this.unsubscribe()
 ```
 
-`detectedActivities` is an object with keys for each detected activity, each of which have an integer value from 0 to 100
+`detectedActivities` is an object with keys for each detected activity, each of which have an integer percentage (0-100)
 indicating the likelihood that the user is performing this activity. For example:
 
 ```js
@@ -114,6 +115,22 @@ indicating the likelihood that the user is performing this activity. For example
 }
 ```
 
+Additionally, the `detectedActivities.sorted` getter is provided which returns an array of activities, ordered by their
+confidence value:
+
+```js
+[
+  { type: 'STILL', confidence: 77 },
+  { type: 'IN_VEHICLE', confidence: 15 },
+  { type: 'ON_FOOT', confidence: 8 },
+  { type: 'WALKING', confidence: 8 },
+]
+```
+
+Because the activities are sorted by confidence level, the first value will be the one with the highest probability.
+Note that ON_FOOT and WALKING are related but won't always have the same value. I have never seen WALKING with a higher
+confidence than ON_FOOT, but it may happen that WALKING comes before ON_FOOT in the array if they have the same value.
+
 The following activity types are supported:
 
 - IN_VEHICLE
@@ -132,15 +149,11 @@ Starts listening for activity updates. The detectionIntervalMillis is passed to
 
 ### `subscribe(callback: Function): Function`
 Subscribes a callback function to be invoked on each activity update. Returns a function which can be called in order to unsubscribe.
-The update callback will be invoked with an object representing the detected activities and their confidence percentage.
+The update callback will be invoked with the detectedActivities object.
 
 ### `stop(): void`
 Stops listening for activity updates.
 
-### `getMostProbableActivity(detectedActivities: Object): Object`
-Util function to determine the most probable activity `type` and its `confidence` percentage based on the detectedActivities object used in the `subscribe` callback.
-For example: `{ type: 'STILL', confidence: 77 }`
-
 ## Credits / prior art
 
 The following projects were very helpful in developing this library:

index.js

@@ -1,19 +1,18 @@
-const { DeviceEventEmitter, NativeModules } = require('react-native');
-const { ActivityRecognition } = NativeModules;
+const { DeviceEventEmitter, NativeModules } = require('react-native')
+const { ActivityRecognition } = NativeModules
 
-ActivityRecognition.subscribe = function subscribe(callback) {
-  const subscription = DeviceEventEmitter.addListener('DetectedActivity', activities => callback(activities))
-  return () => DeviceEventEmitter.removeSubscription(subscription)
-}
+ActivityRecognition.subscribe = subscribe
 
-ActivityRecognition.getMostProbableActivity = function getMostProbableActivity(detectedActivities) {
-  const mostProbableType = Object.keys(detectedActivities).reduce((acc, type) => {
-    return detectedActivities[acc] > detectedActivities[type] ? acc : type
+function subscribe(callback) {
+  const subscription = DeviceEventEmitter.addListener('DetectedActivity', detectedActivities => {
+    Object.defineProperty(detectedActivities, 'sorted', {
+      get: () => Object.keys(detectedActivities)
+        .map(type => ({ type: type, confidence: detectedActivities[type] }))
+        .sort((a, b) => b.confidence - a.confidence),
+    })
+    callback(detectedActivities)
   })
-  return {
-    type: mostProbableType,
-    confidence: detectedActivities[mostProbableType],
-  }
+  return () => DeviceEventEmitter.removeSubscription(subscription)
 }
 
 module.exports = ActivityRecognition