How to perform some action when the system date changes?

Question

There are a list of dates in my program and whenever we start the app (or whenever the system date changes), the app should check and remove the dates which are in the past.

I've tried the following code but it doesn't really work

delDateRef = FirebaseDatabase.getInstance().getReference();
        Date today1 = new Date();
        Date tomorrow = new Date(today1.getTime() + (1000 * 60 * 60 * 24));
        for (int i=0; i<dates.size(); i++) {
            if (dates.get(i).before(tomorrow)) {
                Toast.makeText(RoomDetails.this, "Here", Toast.LENGTH_SHORT).show();
                delDateRef = delDateRef.child("venues").child(roomNo).child("bookings").child(parentNodes.get(i));
                delDateRef.removeValue();
                singleBookingItemList.remove(i);
                parentNodes.remove(i);
                i--;
                roomBookingsAdapter.notifyDataSetChanged();

            }
        }

If today's date is X, it should stay. But once today's date changes and the current day is X+1, the date X should be removed from the list of dates.

Answer 1

Try this:

final Handler someHandler = new Handler(getMainLooper());   
        someHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                tvClock.setText(new SimpleDateFormat("HH:mm", Locale.US).format(new Date()));
                someHandler.postDelayed(this, 1000);
            }
        }, 10);

Answer 2

To remove all past/old dates from a list of dates use the method

private ArrayList<Date> getActiveDates(ArrayList<Date> all_dates) {
    //sort array for faster loop
    Arrays.sort(all_dates.toArray());
    Date today = new Date();
    ArrayList<Date> today_and_future = all_dates;
    for(Date curDate : all_dates){
        if (curDate.compareTo(today) >= 0){
            //we have gotten past all old dates
            //break from loop
            break;
        }
        //remove old date
        today_and_future.remove(curDate);
    }
    return today_and_future;
 }

Call from your code

    delDateRef = FirebaseDatabase.getInstance().getReference(); 
    for (Date activeDate : getActiveDates(dates)) { 
          ...
          //make use of activeDate object here
          ...
    }