Toggle Button Android

JAVA FILE

package com.example.viraj.blog_6_togglebutton;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.CompoundButton;
import android.widget.TextView;
import android.widget.ToggleButton;

public class MainActivity extends AppCompatActivity {
private TextView showtext;
    private ToggleButton tgb1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tgb1=(ToggleButton)findViewById(R.id.id_toggleButton);
        showtext=(TextView)findViewById(R.id.id_2_textView);
        tgb1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if (isChecked)
                {
                    showtext.setVisibility(View.VISIBLE);
                    showtext.setText("visible");
                }
                else
                {
                    showtext.setVisibility(View.INVISIBLE);
                }
            }
        });
    }
}

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_6_togglebutton.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        android:text="TOGGLE BUTTON ON OFF"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.451"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.095"
        android:id="@+id/textView" />

    <ToggleButton
        android:id="@+id/id_toggleButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ToggleButton"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="128dp"
        app:layout_constraintTop_toBottomOf="@+id/textView"
        app:layout_constraintHorizontal_bias="0.521" />

    <TextView
        android:id="@+id/id_2_textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:textSize="24sp"
        android:visibility="invisible"
        android:layout_marginTop="90dp"
        app:layout_constraintTop_toBottomOf="@+id/id_toggleButton"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent" />

</android.support.constraint.ConstraintLayout>