Different behavior when connected to laptop

Question

I wrote an application that logs data coming from my smartphone's sensors. I have a thread that writes this data to a file every hour. When hooked to my laptop, the app works fine. Every hour a new file is created.

But when the smartphone is disconnected from a laptop it doesn't do that. It doesn't crash but the app ran the whole night and only one file was created...

My code uses Thread.sleep() is this an issue?

I am testing this an a Nexus 5 with android 4.4.4

    @Override
    public void run()
    {
        String filename = "";
        String directory = "";
        Date now = new Date();

        while (!stopped)
        {
            Log.i(TAG, "Start the one hour sleep");
            sleepForOneHour(now);
            now = new Date();

            directory = directoryDateFormat.format(now);
            filename = filenameDateFormat.format(now);

            Log.i(TAG, "Write data to SD-card");
            setFileWriteDirectory(directory);
            writeDataToSdCard(filename);
        }
        super.run();
    }

    private void sleepForOneHour(Date filesWritten)
    {
        Date now = new Date();
        long nowMillies = now.getTime();
        long filesWrittenMillies = filesWritten.getTime();

        long passedMillies = (nowMillies - filesWrittenMillies);

        long milliesPerHour = (60 * 60 * 1000);

        long waitMillies = (milliesPerHour - passedMillies);

        try
        {
            sleep(waitMillies);
        } catch (InterruptedException e)
        {
            Log.d(TAG, "Interrupted sleep in filehandler thread");
        }
    }

UPDATE

I tried using Android.Timer instead of Thread.sleep but this gave the same result.

Answer 1

When the phone is not connected to a laptop, it seems that some threads are not executed anymore. Timers and sleeping threads are apparently one of them.

The solution that work for me is to use a WAKE_LOCK. This does seriously affect the power consumption...

In the onCreate of my main Activity I acquire a WAKE_LOCK like this.

private static WakeLock lockStatic;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    PowerManager mgr = (PowerManager) this.getSystemService(Context.POWER_SERVICE);
    lockStatic = mgr.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
    lockStatic.setReferenceCounted(true);
    lockStatic.acquire();
    ...
}

I release the wakelock in the onDestroy. This is not recommended because this will cause the battery to drain a lot faster, but I use the phone as a dedicated logging device, so I don't care that much about the battery life.

@SuppressLint("Wakelock")
@Override
protected void onDestroy()
{
    ...
    lockStatic.release();
    super.onDestroy();
}