Calculate the age using the date of birth

Question

I am developing an android app to find the age from the date of birth provided by user.. three edit-texts are there one for day and other two for month and year. I got the c

Answer 1

You should add a click listener to your button, then in it, calculate the age and display it in your TextView.

public class MainActivity extends Activity {

    long a =0;

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

        final EditText et1 = (EditText) findViewById (R.id.editText1);
        final EditText et2 = (EditText) findViewById (R.id.editText2);
        final EditText et3 = (EditText) findViewById (R.id.editText3);
        Button btn1  = (Button)   findViewById (R.id.button1)  ;
        final TextView tv1 = (TextView) findViewById (R.id.textView1);

        btn1.setOnClickListener(new OnClickListener{
            @Override
            public void onClick (View v){
                int day = Integer.parseInt(et1.getText().toString());
                int month = Integer.parseInt(et2.getText().toString());
                int year = Integer.parseInt(et3.getText().toString());

                tv1.setText(String.valueOf(MainActivity.this.getAge(year, month, day)));
            }
        });
    }


    public int getAge (int _year, int _month, int _day) {

        GregorianCalendar cal = new GregorianCalendar();
        int y, m, d, a;         

        y = cal.get(Calendar.YEAR);
        m = cal.get(Calendar.MONTH);
        d = cal.get(Calendar.DAY_OF_MONTH);
        cal.set(_year, _month, _day);
        a = y - cal.get(Calendar.YEAR);
        if ((m < cal.get(Calendar.MONTH))
                        || ((m == cal.get(Calendar.MONTH)) && (d < cal
                                        .get(Calendar.DAY_OF_MONTH)))) {
                --a;
        }
        if(a < 0)
                throw new IllegalArgumentException("Age < 0");
        return a;
    }

}

Answer 2

tl;dr

Period.between( 
    LocalDate.of( Integer.parseInt( … ) , … , … ) ,  // ( year, month, dayOfMonth )
    LocalDate.now( ZoneId.of( "Pacific/Auckland" ) ) 
).getYears()

Details

You are using troublesome old date-time classes, now legacy, supplanted by the java.time classes.

The LocalDate class represents a date-only value without time-of-day and without time zone.

Unlike the legacy classes, the months have sane numbering, 1-12 for January-December.

LocalDate localDate = LocalDate.of( Integer.parseInt( … ) , … , … ) ;  // year , month , day

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );

Representing a span of time in granularity of days-months-years is done with the Period class.

Period age = Period.between( localDate , today );

To get a String in standard ISO 8601 format, call age.toString(). Or interrogate for each part, years, months, days.

int y = age.getYears();
int m = age.getMonths();
int d = age.getDays();

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Answer 3

First create a class:

public class AgeCalculation {

private int startYear;
private int startMonth;
private int startDay;
private int endYear;
private int endMonth;
private int endDay;
private int resYear;
private int resMonth;
private int resDay;
private Calendar start;
private Calendar end;

public String getCurrentDate() {
    end = Calendar.getInstance();
    endYear = end.get(Calendar.YEAR);
    endMonth = end.get(Calendar.MONTH);
    endMonth++;
    endDay = end.get(Calendar.DAY_OF_MONTH);
    return endDay + ":" + endMonth + ":" + endYear;
}

public void setDateOfBirth(int sYear, int sMonth, int sDay) {
    startYear = sYear;
    startMonth = sMonth;
    startDay = sDay;

}

public int calcualteYear() {
    resYear = endYear - startYear;

    if (endMonth < startMonth){

        resYear --;

    }


    return resYear;

}

public int calcualteMonth() {
    if (endMonth >= startMonth) {
        resMonth = endMonth - startMonth;
    } else {
        resMonth = endMonth - startMonth;
        resMonth = 12 + resMonth;
        resYear--;
    }

    return resMonth;
}

public int calcualteDay() {

    if (endDay >= startDay) {
        resDay = endDay - startDay;
    } else {
        resDay = endDay - startDay;
        resDay = 30 + resDay;
        if (resMonth == 0) {
            resMonth = 11;
            resYear--;
        } else {
            resMonth--;
        }

    }

    return resDay;
}

public String getResult() {
    return resDay + ":" + resMonth + ":" + resYear;
}


public String dob (int sYear, int sMonth, int sDay) {
    startYear = sYear;
    startMonth = sMonth;
    startDay = sDay;

    return  startDay + "/" + startMonth + "/" + startYear;

}

}

then simply call these method in your activity

AgeCalculation age = new AgeCalculation ();
  age.getCurrentDate();
  age.setDateOfBirth(getYear, getMonth, getDate);
  int calculatedYear =  age.calcualteYear();
  int calculatedMonth = age.calcualteMonth();
  int calculatedDate = age.calcualteDay();

Answer 4

In button click just pass the values from edit text boxes to the method and display the return value in textview...