Communicating with the UI Thread Android: User Inactivity

Question

I have a Android application that verifies the user inactivity through a Handler. But I would like know if my Handler implementation is the best solution in my case.

The code:

public abstract class UserInteractionControlActivity extends Activity {

    private static final int SESSION_TIME_OUT = 300000;
    private static final int SESSION_DELAY_TIME = 60000;

    private final Handler mHandler = new Handler(Looper.getMainLooper());

    private long mLastUserInterationTime;

    protected void onResume() {
        super.onResume();
        mHandler.postDelayed(new UserInteractionControl(), SESSION_TIME_OUT);
        Log.i("LOG_KEY", "HANDLER FIRST POST!");
    }

    public void onUserInteraction() {
        super.onUserInteraction();
        mLastUserInterationTime = System.currentTimeMillis();
    }

    private final class UserInteractionControl implements Runnable {

        public void run() {
            long currentTime = System.currentTimeMillis();
            long inactiveTime = currentTime - mLastUserInterationTime;
            if (inactiveTime > SESSION_TIME_OUT) {
                Log.i("LOG_KEY", "TIME OUT!");
            } else {
                mHandler.postDelayed(new UserInteractionControl(), SESSION_DELAY_TIME);
                Log.i("LOG_KEY", "HANDLER POST AGAIN!");
            }
        }
    }
}

My main questions are:

1) What is the difference between instantiate Handler using new Handler(Looper.getMainLooper()) and getWindow().getDecorView().getHandler()?

2) The use of System.currentTimeMillis() in this context is secure?

The use of System.currentTimeMillis() in this context is secure? What do you mean? — Kristy Welsh, Jan 15 '15 at 16:42
Thanks for you comment @KristyWelsh! I asked this question because I do not know if the `System.currentTimeMillis()` will be amended in case the user change the time on Android OS. Because as I am trying to control user idle time, this would be a problem! — falvojr, Jan 15 '15 at 16:47
@Willis: "context" should not have been marked up as code - it was used in the literal sense. — corsair992, Jan 17 '15 at 23:57
1) They are both functionally the same. 2) You can use `SystemClock.uptimeMillis()` instead. — corsair992, Jan 17 '15 at 23:58
Thank you for the comments @corsair992! Already fixed the question! — falvojr, Jan 19 '15 at 00:19
Regarding the question of how to get a Handler object, this information may be of interest: http://codereview.stackexchange.com/a/114723/92925 — RenniePet, Dec 22 '15 at 07:16

score 3 · Accepted Answer · answered Jan 18 '15 at 21:23

1) As @corsair992 said, they should be equivalent, however I think having your own instance of Handler is preferable, as you explicitly control it. If you need to remove any pending Runnable instances later, you can just do a removeCallbacksAndRunnables(null); to remove any messages that your Handler has posted without affecting the decor view's Handler.

2) Don't use System.currentTimeMillis(). SystemClock.elapsedRealtime() is a much better indicator of elapsed time, as it won't be affected by the user changing the Date/Time (whereas currentTimeMillis() does change).

Thank you for answering @kcoppock! Both questions have been resolved! Thanks again! — falvojr, Jan 19 '15 at 00:23

Communicating with the UI Thread Android: User Inactivity

1 Answers1