CIRCLE – AREA AND PERIMETER

Activity_main.xml

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

<androidx.constraintlayout.widget.ConstraintLayout 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"
tools:context=".MainActivity">

<EditText
    android:id="@+id/num"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="97dp"
    android:layout_marginTop="148dp"
    android:layout_marginEnd="104dp"
    android:layout_marginBottom="538dp"
    android:ems="10"
    android:inputType="number"

    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    tools:ignore="SpeakableTextPresentCheck,TouchTargetSizeCheck" />

<TextView
    android:id="@+id/ans"
    android:layout_width="141dp"
    android:layout_height="42dp"
    android:layout_marginStart="125dp"
    android:layout_marginTop="43dp"
    android:layout_marginEnd="145dp"
    android:layout_marginBottom="452dp"
    android:text="ans"
    android:textSize="15dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/num" />

<Button
    android:id="@+id/area"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="54dp"
    android:layout_marginTop="26dp"
    android:layout_marginEnd="79dp"
    android:layout_marginBottom="378dp"
    android:text="area"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toStartOf="@+id/perimeter"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/ans"
    app:layout_constraintVertical_bias="1.0" />

<Button
    android:id="@+id/perimeter"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="80dp"
    android:layout_marginTop="22dp"
    android:layout_marginEnd="88dp"
    android:layout_marginBottom="382dp"
    android:text="perimeter"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/area"
    app:layout_constraintTop_toBottomOf="@+id/ans"
    app:layout_constraintVertical_bias="1.0" />

</androidx.constraintlayout.widget.ConstraintLayout>

Mainactivity.java
package com.example.circle;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {
private EditText n1;
private TextView t1;
private Button b1,b2;
Double r,a,b;
Double pi =3.14;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);
    n1 = (EditText) findViewById(R.id.num);
    t1 = (TextView) findViewById(R.id.ans);
    b1 = (Button)  findViewById(R.id.area);
    b2 = (Button) findViewById(R.id.perimeter);

    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            r = Double.parseDouble(n1.getText().toString());
            a = pi*r*r;
            t1.setText("Area : "+a);
        }
    });

    b2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            r = Double.parseDouble(n1.getText().toString());
            b = 2*pi*r;
            t1.setText("Perimeter : "+b);
        }
    });

}

}