Write a Android code to calculate area of triangle:

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">

</androidx.constraintlayout.widget.ConstraintLayout>

Main_activity.java
package com.example.triangle;

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,n2,n3;
private TextView t1;
private Button b1,b2;
Double side1,side2,side3,area1,perimeter1;

}