How to Build Age Calculator in Android Studio? - RSM Developer

Build Age Calculator in Android Studio

Step 1: Creating a new project

• Open a new project.
• We will be working on Empty Activity with language as Java. Leave all other options unchanged.
• You can change the name of the project at your convenience.
• There will be two default files named activity_main.xml and MainActivity.java.

Step 2: Navigate to Build scripts > build.gradle(module) file and add the following dependency to it

//Age Calculater
implementation 'joda-time:joda-time:2.9.1'

Step 3: Working with the activity_main.xml file

Here we will design the user interface of our application. We will be using the following components for their respective works:

• Button 1: to pick the first date user wants to enter.
• Button 2: to pick the second date user wants to enter.
• Button 3: to perform the calculation
• TextView: to show the final output(age).

Navigate to the app > res > layout > activity_main.xml and add the below code to that file.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/white"
    tools:context=".MainActivity">

    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:orientation="vertical"
        android:padding="10dp"
        tools:context=".MainActivity">

        <!-- linear layout to show datepickers-->

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <!-- to select the first date-->

            <Button
                android:id="@+id/bt_birth"
                android:layout_width="150dp"
                android:layout_height="50dp"
                android:backgroundTint="#ff0000"
                android:text="01/01/2021"
                android:textColor="@color/white"
                android:textSize="13sp" />
            
            <!-- displaying message as "to"-->

            <TextView
                android:layout_width="100dp"
                android:layout_height="50dp"
                android:gravity="center_horizontal"
                android:text="To"
                android:textColor="@color/black"
                android:textSize="20sp"
                android:textStyle="bold" />
            
            <!-- to display date number 2-->

            <Button
                android:id="@+id/bt_today"
                android:layout_width="145dp"
                android:layout_height="50dp"
                android:backgroundTint="#009688"
                android:textColor="@color/black"
                android:textSize="13sp" />

        </LinearLayout>

        <!-- to perform the calculation-->

        <Button
            android:id="@+id/btn_calculate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:text="calculate" />
        
        <!-- to display the message "Result"-->

       <TextView

    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="50dp"
    android:text="Result"
    android:textColor="@color/white"
    android:textSize="30sp"
    android:textStyle="bold" />

        <!-- To show the final output(age)-->

      <TextView

    android:id="@+id/tv_result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="10dp"
    android:background="#2196F3"
    android:text="0 Years | 0 Months | 0 Days"
    android:textSize="25sp"
    android:textColor="@color/white"
    android:textStyle="bold" />

    </LinearLayout>

</LinearLayout>

Step 4: Working with MainActivity.java file

In MainActivity.java file onClickListener is used on buttons to pick the date and to perform the calculation. Use the following code in the MainActivity.java file.

package com.rsmdeveloper.agecalculater;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

import android.app.DatePickerDialog;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;

import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;
import android.widget.Toast;

import org.joda.time.Period;
import org.joda.time.PeriodType;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    // initializing variables

    Button btn_birth, btn_today, btn_calculate;

    TextView tvResult;

    DatePickerDialog.OnDateSetListener dateSetListener1, dateSetListener2;

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

        // assign variables

        btn_birth = findViewById(R.id.bt_birth);
        btn_today = findViewById(R.id.bt_today);
        btn_calculate = findViewById(R.id.btn_calculate);
        tvResult = findViewById(R.id.tv_result);

        // calendar format is imported to pick date
        Calendar calendar = Calendar.getInstance();

        // for year
        int year = calendar.get(Calendar.YEAR);

        // for month
        int month = calendar.get(Calendar.MONTH);

        // for date
        int day = calendar.get(Calendar.DAY_OF_MONTH);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd/MM/yyyy");

        // to set the current date as by default
        String date = simpleDateFormat.format(Calendar.getInstance().getTime());
        btn_today.setText(date);

        // action to be performed when button 1 is clicked
        btn_birth.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // date picker dialog is used
                // and its style and color are also passed
                DatePickerDialog datePickerDialog = new DatePickerDialog(MainActivity.this, android.R.style.Theme_Holo_Light_Dialog_MinWidth, dateSetListener1, year, month, day

                );

                // to set background for datepicker
                datePickerDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
                datePickerDialog.show();
            }

        });

        // it is used to set the date which user selects
        dateSetListener1 = new DatePickerDialog.OnDateSetListener() {
            @Override
            public void onDateSet(DatePicker view, int year, int month, int day) {
                // here month+1 is used so that
                // actual month number can be displayed
                // otherwise it starts from 0 and it shows
                // 1 number less for every month
                // example- for january month=0
                month = month + 1;
                String date = day + "/" + month + "/" + year;
                btn_birth.setText(date);
            }

        };

        // action to be performed when button 2 is clicked
        btn_today.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // date picker dialog is used
                // and its style and color are also passed
                DatePickerDialog datePickerDialog = new DatePickerDialog(MainActivity.this, android.R.style.Theme_Holo_Light_Dialog_MinWidth, dateSetListener2, year, month, day);
                // to set background for datepicker
                datePickerDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
                datePickerDialog.show();
            }
        });

        // it is used to set the date which user selects
        dateSetListener2 = new DatePickerDialog.OnDateSetListener() {
            @Override
            public void onDateSet(DatePicker view, int year, int month, int day) {
                // here month+1 is used so that
                // actual month number can be displayed
                // otherwise it starts from 0 and it shows
                // 1 number less for every month
                // example- for january month=0
                month = month + 1;
                String date = day + "/" + month + "/" + year;
                btn_today.setText(date);
            }
        };

        // action to be performed when calculate button is clicked
        btn_calculate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // converting the inputted date to string
                String sDate = btn_birth.getText().toString();
                String eDate = btn_today.getText().toString();
                SimpleDateFormat simpleDateFormat1 = new SimpleDateFormat("dd/MM/yyyy");
                try {
                    // converting it to date format
                    Date date1 = simpleDateFormat1.parse(sDate);
                    Date date2 = simpleDateFormat1.parse(eDate);
                    long startdate = date1.getTime();
                    long endDate = date2.getTime();

                    // condition
                    if (startdate <= endDate) {
                        org.joda.time.Period period = new Period(startdate, endDate, PeriodType.yearMonthDay());
                        int years = period.getYears();
                        int months = period.getMonths();
                        int days = period.getDays();

                        // show the final output
                        tvResult.setText(years + " Years |" + months + "Months |" + days + "Days");
                    } else {
                        // show message
                        Toast.makeText(MainActivity.this, "BirthDate should not be larger than today's date!", Toast.LENGTH_SHORT).show();
                    }
                } catch (ParseException e) {
                    e.printStackTrace();
                }
            }
        });

    }
}

Output:

Now run the App and you will see main topics and sub-topics listed.....