Get System Time and add 30 minutes to it, after that compare it with another system time

Question

Actually I want to disable a button for 30 minutes.

The code below works well but if we kill the application and open it within 30 minutes, the button is now enabled.

public static void timmer(final ImageButton btn){
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            isTimerRunning = false;
            btn.setEnabled(true);
        }

    }, 1800000);
}

Now I am geting the system time on button click and then adds 30 minutes to it and save it to DataManager (single class for user object). Again on button click I am comparing the save time with current system time.

 @OnClick(R.id.generalReportBtn)
    public void setGeneralReport(ImageButton button) {
    Log.e("Data Manager Time: ",DataManager.getInstance().getCurrentUser().getLastTime().MINUTE+"");
    Log.e("Current Time: ", java.util.Calendar.getInstance().MINUTE+"");
    if(DataManager.getInstance().getCurrentUser().getLastTime().after(java.util.Calendar.getInstance())){
      DataManager.getInstance().getCurrentUser().lastTime.set(java.util.Calendar.getInstance().YEAR,java.util.Calendar.getInstance().MONTH,java.util.Calendar.getInstance().DATE,java.util.Calendar.getInstance().HOUR_OF_DAY,java.util.Calendar.getInstance().MINUTE,java.util.Calendar.getInstance().SECOND);
    DataManager.getInstance().getCurrentUser().lastTime.add(DataManager.getInstance().getCurrentUser().lastTime.MINUTE,30);

    }else if(Utilities.isFirstTimePressed){
        Utilities.isFirstTimePressed = false;
        DataManager.getInstance().getCurrentUser().lastTime.set(java.util.Calendar.getInstance().YEAR,java.util.Calendar.getInstance().MONTH,java.util.Calendar.getInstance().DATE,java.util.Calendar.getInstance().HOUR_OF_DAY,java.util.Calendar.getInstance().MINUTE,java.util.Calendar.getInstance().SECOND);
    DataManager.getInstance().getCurrentUser().lastTime.add(DataManager.getInstance().getCurrentUser().lastTime.MINUTE,30);

    }else {
        Toast.makeText(mainclass,"Button is disabled for 30 minutes",Toast.LENGTH_SHORT).show();
    }
}

But this code also did't work for me.

score 2 · Answer 1 · answered Oct 05 '17 at 17:47

Start by setting a variables. Then your code will be easier to read:

java.util.Calendar cal = java.util.Calendar.getInstance();
User user = DataManager.getInstance().getCurrentUser();

Then use those variables instead of calling Calendar.getInstance() so many times.

You're mixing up constants and values. YEAR is a constant that you use when you want to the year value.

Instead of this (which will always return the same value since it is a constant):

java.util.Calendar.getInstance().YEAR

Use this:

cal.get(Calendar.YEAR)

Do that for all your YEARs, MONTHs, etc, and everything will work.

score 2 · Answer 2 · answered Oct 05 '17 at 17:48

Calendar.getInstance().YEAR is a constant that represents the year field (which has a value equals to 1). Actually, it's the same as calling Calendar.YEAR directly.

But this is not the year value of the Calendar object. When you do set(java.util.Calendar.getInstance().YEAR you're setting the year to 1 (which is probably not what you want). The same applies for MONTH, MINUTE and all other constants you're using.

Another detail is that you don't need to create another calendar (by calling Calendar.getInstance()) all the time. That's redundant and not necessary in your code.

Anyway, first things first. In the first 2 lines, you're printing the MINUTE constant, not the minutes value of the dates. If you want to print the full date (which is much more useful than just the minutes, IMO), just call the getTime() method. Also, set the values to variables before using them, it makes the code much cleaner:

import java.util.Calendar;

Calendar lastTime = DataManager.getInstance().getCurrentUser().getLastTime();
Calendar now = Calendar.getInstance(); // current date/time
Log.e("Data Manager Time: ", lastTime.getTime() + "");
Log.e("Current Time: ", now.getTime() + "");

Just reminding that this will print the dates in the device's JVM default timezone. If you want to change the format, just check in this link.

If you still want to print just the minutes, change the call to getTime() to get(Calendar.MINUTE).

Now the rest of your logic (if I understood correctly) will be like this:

if (lastTime.after(now)) {
    lastTime = (Calendar) now.clone(); // lastTime becomes a copy of "now"
    lastTime.add(Calendar.MINUTE, 30); // add 30 minutes
} else if (Utilities.isFirstTimePressed) {
    Utilities.isFirstTimePressed = false;
    lastTime.add(Calendar.MINUTE, 30); // add 30 minutes
} else {
    Toast.makeText(mainclass, "Button is disabled for 30 minutes", Toast.LENGTH_SHORT).show();
}

Java new Date/Time API

The old classes (Date, Calendar and SimpleDateFormat) have lots of problems and design issues, and they're being replaced by the new APIs.

In Android you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes. To make it work, you'll also need the ThreeTenABP (more on how to use it here).

One way to check if 30 minutes has passed is to use the org.threeten.bp.Instant class. Then you use the isAfter method to compare, and a org.threeten.bp.temporal.ChronoUnit to add 30 minutes.

I also use a org.threeten.bp.ZoneId to convert the date to the JVM default timezone (just to print it). In this link there are also answers that cover the new API, using a DateTimeFormatter, so you can refer to them if you want to change the format.

I also use the org.threeten.bp.DateTimeUtils class to convert from and to java.util.Calendar. The code will be like this:

// convert java.util.Calendar to org.threeten.bp.Instant
Instant lastTime = DateTimeUtils.toInstant(DataManager.getInstance().getCurrentUser().getLastTime());
Instant now = Instant.now();
Log.e("Data Manager Time: ", lastTime.atZone(ZoneId.systemDefault()) + "");
Log.e("Current Time: ", now.atZone(ZoneId.systemDefault())  + "");
if (lastTime.isAfter(now)) {
    // add 30 minutes to current date/time
    lastTime = now.plus(30, ChronoUnit.MINUTES);
} else if (Utilities.isFirstTimePressed) {
    Utilities.isFirstTimePressed = false;
    lastTime = lastTime.plus(30, ChronoUnit.MINUTES);
} else {
    Toast.makeText(mainclass, "Button is disabled for 30 minutes", Toast.LENGTH_SHORT).show();
}

// convert back to java.util.Calendar (set it anywhere you need)
DateTimeUtils.toGregorianCalendar(lastTime.atZone(ZoneId.systemDefault()));

I'm using ZoneId.systemDefault(), which takes the JVM default timezone (the same used when you create Calendar.getInstance(), so it usually won't be much a problem, unless the user changes it).

The problem is that the default timezone can be changed, even at runtime, so the ideal is to specify one, if you possibly can. The API uses IANA timezones names (always in the format Region/City, like America/Sao_Paulo or Europe/Berlin). Avoid using the 3-letter abbreviations (like CST or PST) because they are ambiguous and not standard.

You can get a list of available timezones (and choose the one that fits best your system) by calling ZoneId.getAvailableZoneIds().

score 0 · Answer 3 · answered Oct 06 '17 at 04:24

Easy way is to get Systems TimeStamp like:

long systemTime = System.currentTimeMillis()

Add 30 minutes to it.

systemTime += 180000 //(180000 miliseconds is equivalent to 30 minutes)

Store it to shared preferences. Now get the value from shared preferences and compare with the current time.

Get System Time and add 30 minutes to it, after that compare it with another system time

3 Answers3

Java new Date/Time API