Add a certain amount of time to a current time and write it

Question

I'm using:

Calendar c = Calendar.getInstance();

with which i get a current time,

String sHour = c.get(Calendar.HOUR_OF_DAY)
String sMinute = c.get(Calendar.MINUTE)

What i need is to add e.g. 1 Hour 10 Minutes - store it in a variable and also Substract let's say 10 minutes and save that as an another variable. (I need to use them both in a TextView)

I've seen the add(); method in Android documentation but I can't seem to understand how it works. Thanks

Answer 1

The code you've posted won't compile, as Calendar.get() doesn't return a string. You should also note that calendar is mutable - it's not like each call to add returns a new calendar. So you'll need to create a new instance each time you want a separate variable for a different value. For example:

Calendar now = Calendar.getInstance();

Calendar tmp = (Calendar) now.clone();
tmp.add(Calendar.HOUR_OF_DAY, 1);
tmp.add(Calendar.MINUTE, 10);
Calendar nowPlus70Minutes = tmp;

tmp = (Calendar) now.clone();
tmp.add(Calendar.MINUTE, -10);
Calendar nowMinus10Minutes = tmp;

If at all possible, I'd strongly recommend that you use Joda Time instead of Calendar/Date - it's a far superior API. You may want to trim the time zones included with it, however, so that it's faster to get started and less overhead in your apk.

Answer 2

You can simply call System.currentTimeMillis() + INTERVAL.

Where INTERVAL is the interval in milliseconds (for example:

public static final long INTERVAL = 1000 * 60 * 60 * 24; // 1 day