MalcomActivityLifecycleCallbacks.java

package com.malcom.library.android;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.util.activitylifecyclecallbackscompat.MalcomActivityLifecycleCallbacksCompat;

import com.malcom.library.android.module.core.MCMCoreAdapter;
import com.malcom.library.android.module.stats.MCMStats;

import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Keeps track of the opened activities to know when the user starts and finishes using the app
 * to signal the start and end of a beacon.
 *
 * It understands that the user starts using the app (beacon start) when a new activity starts
 * and the user is not in the middle of a session. And it understands that the user finishes
 * using the app when an activity stops and there are no activities started for a little while.
 */
public class MalcomActivityLifecycleCallbacks implements MalcomActivityLifecycleCallbacksCompat
{
	/** Number of activities that are started in any given moment */
    private static AtomicInteger startedActivities = new AtomicInteger(0);

	/** Wether the user is in the middle of a "session". We use it to know when to signal the start/end beacon. */
	private static AtomicBoolean inTheMiddleOfASession = new AtomicBoolean(false);

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        // Patch to fix a bug: https://github.com/MyMalcom/malcom-lib-android/issues/30
        MCMStats.initContext(activity.getApplicationContext());
    }

    @Override
    public void onActivityStarted(Activity activity)
	{
		int numActivities = startedActivities.incrementAndGet();
		final boolean wasInTheMiddleOfASession = inTheMiddleOfASession.getAndSet(true);

		if (Log.isLoggable(MCMDefines.LOG_TAG, Log.DEBUG))
			Log.d(MCMDefines.LOG_TAG, "Activity started (total: " + numActivities + ", in session: " + wasInTheMiddleOfASession + ")");

		if (!wasInTheMiddleOfASession) {
            Log.d(MCMDefines.LOG_TAG, "An activity started and there's no current session: Malcom session starts");
            MCMCoreAdapter.getInstance().moduleStatsStartBeacon(activity.getApplicationContext(),true);
        }
    }

    @Override
    public void onActivityResumed(Activity activity) {
		// Nothing to do
    }

    @Override
    public void onActivityPaused(Activity activity) {
		// Nothing to do
    }

    @Override
    public void onActivityStopped(Activity activity)
	{
		int numActivities = startedActivities.decrementAndGet();

		if (Log.isLoggable(MCMDefines.LOG_TAG, Log.DEBUG))
			Log.d(MCMDefines.LOG_TAG, "Activity ended   (total: " + numActivities + ")");

		signalEndBeaconIfNoActivitesStarted();
    }

	/**
	 * If no activities are started it signals the end beacon and sets {@link #inTheMiddleOfASession} to false
	 * (it is understood that the user has finished using the app for now).
	 *
	 * When a user changes from one activity to another there could be a lapse where there are no started
	 * activities but immediately there will be one that starts. That's why the number of started activities
	 * is rechecked after a little wait before actually signalling the end beacon.
	 *
	 * See: http://stackoverflow.com/questions/3287666/android-how-to-know-when-an-app-enters-or-the-background-mode/19502860
	 */
	private void signalEndBeaconIfNoActivitesStarted()
	{
		if (startedActivities.get() == 0)
		{
			new Thread()
			{
				@Override
				public void run()
				{
					try {
						Log.d(MCMDefines.LOG_TAG, "No activities started. Waiting a while...");
						Thread.sleep(1000); // TODO: How much we should wait for a new activity to start?
					} catch (InterruptedException e) {
						Log.e(MCMDefines.LOG_TAG, "Unexpected interruption", e);
					}

					if (startedActivities.get() == 0)
					{
						inTheMiddleOfASession.getAndSet(false);
						Log.d(MCMDefines.LOG_TAG, "No activities started for a while: Malcom session ends.");
						MCMCoreAdapter.getInstance().moduleStatsEndBeacon();
					}
					else
						Log.d(MCMDefines.LOG_TAG, "An activity started while waiting. Malcom session hasn't ended yet.");
				}
			}.start();
		}
	}

	@Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
		// Nothing to do
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
		// Nothing to do (we can't count on this method being called)
    }
}