ActivityTrackerService.java

package tw.tobias.reviveandsurvive;


import android.content.Context;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;
import android.util.Log;
import com.google.android.gms.location.ActivityRecognitionResult;
import com.google.android.gms.location.DetectedActivity;

import android.app.IntentService;
import android.content.Intent;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.List;

public class ActivityTrackerService extends IntentService {
    public static final String STATUS_UNKNOWN = "Unknown";
    public static final String STATUS_IN_A_VEHICLE = "In a vehicle";
    public static final String STATUS_ON_FOOT = "On foot";
    public static final String STATUS_TILTING = "Tilting";
    public static final String STATUS_ON_BIKE = "On bike";
    public static final String STATUS_STILL = "Still";
    public static final String STATUS_RUNNING = "Running";

    private static final String PREFS_NAME = "ActivityTrackerState";
    public static final String BROADCAST_ACTION = "tw.tobias.reviveandsurvive";
    private static final String TAG = "ActivityTrackerService";
    public static final String SERIALIZED_HIST_KEY = "serializedHistory";
    private final Gson gson;
    private final Type listOfMeasurementObject;

    private List<Measurement> history;

    public SharedPreferences getSharedPreferences() {
        Context ctx = getApplicationContext();
        return PreferenceManager.getDefaultSharedPreferences(ctx);
    }

    public ActivityTrackerService() {
        super("ActivityRecognitionService");

        gson = new Gson();
        listOfMeasurementObject = new TypeToken<List<Measurement>>(){}.getType();

        Log.d(TAG, "Initialized new ActivityTrackerService");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        if (ActivityRecognitionResult.hasResult(intent)) {
            // Create a new measurement as appropriate
            ActivityRecognitionResult result = ActivityRecognitionResult.extractResult(intent);
            addMeasurement(getActivityName(result.getMostProbableActivity().getType()), result.getTime());

            Log.d(TAG, getLatestMeasurement().toString());

            // Send an intent to users
            Intent uiIntent = new Intent(BROADCAST_ACTION);
            uiIntent.putExtra("currentState", getLatestStatus());
            uiIntent.putExtra("latestMeasurement", getLatestMeasurement().toJson());
            sendBroadcast(uiIntent);
        }
    }

    private String getActivityName(int detectedActivity){
        switch (detectedActivity) {
            case DetectedActivity.IN_VEHICLE:
                return STATUS_IN_A_VEHICLE;

            case DetectedActivity.ON_FOOT:
                return STATUS_ON_FOOT;
            case DetectedActivity.ON_BICYCLE:
                return STATUS_ON_BIKE;
            case DetectedActivity.RUNNING:
                return STATUS_RUNNING;

            case DetectedActivity.STILL:
                return STATUS_STILL;
            case DetectedActivity.TILTING:
                return STATUS_TILTING;

            default:
                Log.w(TAG, "Unknown activity type of " + detectedActivity);
                return STATUS_UNKNOWN;
        }
    }

    public void addMeasurement(String status, long time) {
        loadHistory();

        Measurement latest = getLatestMeasurement();

        Log.i(TAG, "Previous status: " + (latest == null ? "null" : latest.status) + ", new status: " + status);

        if (latest != null && latest.status.equals(status)) {
            Log.d(TAG, "Reusing previous measurement");
            latest.updateMeasurement(time);
        }
        else {
            Log.d(TAG, "Creating new measurement");
            history.add(new Measurement(status, time));
        }
        getSharedPreferences().edit().putString(SERIALIZED_HIST_KEY, gson.toJson(history, listOfMeasurementObject)).apply();

        Log.i(TAG, "History length: " + history.size());
    }

    private void loadHistory () {
        if (history == null) {
            String serializedHistory = getSharedPreferences().getString(SERIALIZED_HIST_KEY, "[]");
            history = gson.fromJson(serializedHistory, listOfMeasurementObject);
        }
    }

    /**
     * Gets the latest measurement taken
     * @return Gets the latest Measurement taken, including its duration and how many times it's been updated
     */
    private Measurement getLatestMeasurement() {
        loadHistory();

        if (history.size() == 0) {
            return null;
        }

        return history.get(history.size() - 1);
    }

    public String getLatestStatus() {
        return getLatestMeasurement().status;
    }
}

Measurement.java

package tw.tobias.reviveandsurvive;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Measurement {
    private static final Type measurementType = new TypeToken<Measurement>(){}.getType();

    long since;
    long lastUpdated;
    String status;
    int measurements;

    public Measurement(String status, long time) {
        this.status = status;
        this.since = time;
        this.lastUpdated = time;
        measurements = 1;
    }

    public void updateMeasurement(long time) {
        lastUpdated = time;
        measurements++;
    }

    public long getDurationMillis() {
        return lastUpdated  - since;
    }

    public String getDurationFormatted(String format) {
        return new SimpleDateFormat(format).format(new Date(getDurationMillis()));
    }

    public String getDurationFormatted() {
        return getDurationFormatted("HH'h' mm'm' ss's'");
    }

    @Override
    public String toString() {
        return "Measurement{" +
                "since=" + since +
                ", lastUpdated=" + lastUpdated +
                ", status='" + status + '\'' +
                ", measurements=" + measurements +
                ", duration=" + getDurationFormatted() +
                '}';
    }

    public static Measurement fromJson(String serialized) {
        return new Gson().fromJson(serialized, measurementType);
    }

    public String toJson() {
        return new Gson().toJson(this, measurementType);
    }
}