timer - Android: How do I display an updating clock in a TextView

Question

have a clock I want to display in a TextView.

I would have thought there was a few nice functions to do this, but I couldn't find anything. I ended up implementing my own way that uses a Handler. What I'm asking though, is there a better (more efficient) way to display a real time updating clock?

private Runnable mUpdateClockTask = new Runnable() {
   public void run() {
       setTime();
       mClockHandler.postDelayed(this, 1000);
   }
};

That's my handler, which runs every second, and then my set time and date function is below

TextView mClockView;

public void setTime() {
    Calendar cal = Calendar.getInstance();
    int minutes = cal.get(Calendar.MINUTE);

    if (DateFormat.is24HourFormat(this)) {
        int hours = cal.get(Calendar.HOUR_OF_DAY);
        mClockView.setText((hours < 10 ? "0" + hours : hours) + ":" + (minutes < 10 ? "0" + minutes : minutes));
    }
    else {
        int hours = cal.get(Calendar.HOUR);
        mClockView.setText(hours + ":" + (minutes < 10 ? "0" + minutes : minutes) + " " + new DateFormatSymbols().getAmPmStrings()[cal.get(Calendar.AM_PM)]);
    }
}

Cheers

Answer 1

Updating the system clock is not like updating a chronometer. We talk about the time changed on the minute (system clock minute and 00 seconds).

Using a Timer is not the right way to do this. It's not only overkill, but you must resort to some tricks to make it right.

The right way to do this (ie. update a TextView showing the time as HH:mm) is to use BroadcastReceiver like this :

BroadcastReceiver _broadcastReceiver;
private final SimpleDateFormat _sdfWatchTime = new SimpleDateFormat("HH:mm");
private TextView _tvTime;

@Override
public void onStart() {
    super.onStart();
    _broadcastReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context ctx, Intent intent) {
                if (intent.getAction().compareTo(Intent.ACTION_TIME_TICK) == 0)
                    _tvTime.setText(_sdfWatchTime.format(new Date()));
            }
        };

    registerReceiver(_broadcastReceiver, new IntentFilter(Intent.ACTION_TIME_TICK));
}

@Override
public void onStop() {
    super.onStop();
    if (_broadcastReceiver != null)
        unregisterReceiver(_broadcastReceiver);
}

The system will send this broadcast event at the exact beginning of every minutes based on system clock. Don't forget however to initialize your TextView beforehand (to current system time) since it is likely you will pop your UI in the middle of a minute and the TextView won't be updated until the next minute happens.