Sum of two no android edit text button textview

java file

package com.example.viraj.blog_3_sumof2number;

import android.support.v7.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 e1;
    private EditText e2;
    private TextView txt;
    private Button b1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        e1 = (EditText) findViewById(R.id.id_noone);
        e2 = (EditText) findViewById(R.id.id_no2);
        txt = (TextView) findViewById(R.id.id_answer);
b1=(Button)findViewById(R.id.id_button) ;

        b1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String gettexte1 = e1.getText().toString();
                String gettexte2 = e2.getText().toString();

                int v1 = Integer.parseInt(gettexte1);
                int v2 = Integer.parseInt(gettexte2);

                int total = v1 + v2;
                txt.setText(Integer.toString(total));
            }
        });

    }
}


xml file

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.example.viraj.blog_3_sumof2number.MainActivity">

    <EditText
        android:id="@+id/id_noone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint="enter text 1"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="114dp"
        app:layout_constraintHorizontal_bias="0.431" />

    <EditText
        android:id="@+id/id_no2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:hint="enter text 2"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="63dp"
        app:layout_constraintTop_toBottomOf="@+id/id_noone"
        app:layout_constraintHorizontal_bias="0.431" />

    <Button
        android:id="@+id/id_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="92dp"
        android:text="Button"
        app:layout_constraintTop_toBottomOf="@+id/id_no2"
        tools:layout_editor_absoluteX="148dp" />

    <TextView
        android:id="@+id/id_answer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_button" />
</android.support.constraint.ConstraintLayout>