How to make age Calculator app in Android Studio

Create a new project in Android Studio and name it “AgeCalculatorApp”.

Open the activity_main.xml file located in the res/layout directory. Replace the existing code with the following XML layout:

<?xml version="1.0" encoding="utf-8"?>
<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:orientation="vertical"
    android:gravity="center"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/label_birthdate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Enter your birthdate:"
        android:textSize="18sp"
        android:textStyle="bold"
        android:layout_marginBottom="16dp" />

    <EditText
        android:id="@+id/edit_birthdate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="date"
        android:layout_marginBottom="16dp" />

    <Button
        android:id="@+id/button_calculate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Calculate"
        android:onClick="calculateAge"
        android:layout_marginBottom="16dp" />

    <TextView
        android:id="@+id/text_result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:layout_marginBottom="16dp" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>

<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:orientation="vertical"

android:gravity="center"

tools:context=".MainActivity">

<TextView

android:id="@+id/label_birthdate"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Enter your birthdate:"

android:textSize="18sp"

android:textStyle="bold"

android:layout_marginBottom="16dp" />

<EditText

android:id="@+id/edit_birthdate"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:inputType="date"

android:layout_marginBottom="16dp" />

<Button

android:id="@+id/button_calculate"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Calculate"

android:onClick="calculateAge"

android:layout_marginBottom="16dp" />

<TextView

android:id="@+id/text_result"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="18sp"

android:layout_marginBottom="16dp" />

</LinearLayout>

Open the MainActivity.java file located in the java/<your_package_name> directory. Replace the existing code with the following Java code:

package com.example.agecalculatorapp;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    private EditText editBirthdate;
    private TextView textResult;

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

        editBirthdate = findViewById(R.id.edit_birthdate);
        textResult = findViewById(R.id.text_result);
    }

    public void calculateAge(View view) {
        String birthdateString = editBirthdate.getText().toString();

        SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy", Locale.getDefault());
        Date currentDate = new Date();

        try {
            Date birthdate = dateFormat.parse(birthdateString);
            long ageInMillis = currentDate.getTime() - birthdate.getTime();

            // Calculate age in years
            long ageInYears = ageInMillis / (1000L * 60L * 60L * 24L * 365L);

            // Calculate age in months
            long ageInMonths = ageInYears * 12;

            // Calculate age in days
            long ageInDays = ageInMillis / (1000L * 60L * 60L * 24L);

            String result = String.format("Age: %d years, %d months, %d days", ageInYears, ageInMonths, ageInDays);
            textResult.setText(result);
        } catch (ParseException e) {
            e.printStackTrace();
            textResult.setText("Invalid date format");
        }
    }
}

package com.example.agecalculatorapp;

import android.os.Bundle;

import android.view.View;

import android.widget.EditText;

import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.Locale;

public class MainActivity extends AppCompatActivity {

private EditText editBirthdate;

private TextView textResult;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

editBirthdate = findViewById(R.id.edit_birthdate);

textResult = findViewById(R.id.text_result);

}

public void calculateAge(View view) {

String birthdateString = editBirthdate.getText().toString();

SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy", Locale.getDefault());

Date currentDate = new Date();

try {

Date birthdate = dateFormat.parse(birthdateString);

long ageInMillis = currentDate.getTime() - birthdate.getTime();

// Calculate age in years

long ageInYears = ageInMillis / (1000L * 60L * 60L * 24L * 365L);

// Calculate age in months

long ageInMonths = ageInYears * 12;

// Calculate age in days

long ageInDays = ageInMillis / (1000L * 60L * 60L * 24L);

String result = String.format("Age: %d years, %d months, %d days", ageInYears, ageInMonths, ageInDays);

textResult.setText(result);

} catch (ParseException e) {

e.printStackTrace();

textResult.setText("Invalid date format");

}

Open the AndroidManifest.xml file located in the app/src/main directory. Replace the existing code with the following:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.agecalculatorapp">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.example.agecalculatorapp">

<application

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:roundIcon="@mipmap/ic_launcher_round"

android:supportsRtl="true"

android:theme="@style/AppTheme">

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

Open the build.gradle (Module: app) file located in the root directory of the project. Ensure that the minSdkVersion is set to 21 or higher:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.example.agecalculatorapp"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    compileOptions {
        sourceCompatibility = 1.8
        targetCompatibility = 1.8
    }

    lintOptions {
        checkReleaseBuilds false
        abortOnError false
    }
}

dependencies {
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.0'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

apply plugin: 'com.android.application'

android {

compileSdkVersion 30

buildToolsVersion "30.0.3"

defaultConfig {

applicationId "com.example.agecalculatorapp"

minSdkVersion 21

targetSdkVersion 30

versionCode 1

versionName "1.0"

testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

}

buildTypes {

release {

minifyEnabled false

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

}

compileOptions {

sourceCompatibility = 1.8

targetCompatibility = 1.8

}

lintOptions {

checkReleaseBuilds false

abortOnError false

}

dependencies {

implementation 'androidx.appcompat:appcompat:1.3.1'

implementation 'androidx.constraintlayout:constraintlayout:2.1.0'

testImplementation 'junit:junit:4.13.2'

androidTestImplementation 'androidx.test.ext:junit:1.1.3'

androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

}

That’s it! You can now build and run the app on an Android device or emulator. The app will allow the user to enter their birthdate and calculate their age in years, months, and days.

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