Custom RadioButton Android

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
   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">
 
   <TextView
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="Select One"
       android:textStyle="bold"
       android:layout_marginLeft="10dp"
       android:textSize="20dp"/>
 
   <!-- add RadioGroup which contain the many RadioButton-->
   <RadioGroup
       android:layout_marginTop="50dp"
       android:id="@+id/groupradio"
       android:layout_marginLeft="10dp"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content">
 
       <!-- In RadioGroup create the 1 Radio Button-->
       <!-- like this we will add some more Radio Button-->
       <RadioButton
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:id="@+id/radia_id1"
           android:text="A"
           android:textSize="20dp"/>
 
       <RadioButton
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:id="@+id/radia_id2"
           android:text="B"
           android:textSize="20dp"/>
 
   </RadioGroup>
 
   <!-- add button For Submit the Selected item-->
   <Button
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="Select"
       android:id="@+id/submit"
       android:textStyle="bold"
       android:textSize="20dp"
       android:layout_marginTop="200dp"
       android:layout_marginLeft="180dp"
       />
 
   <!-- add clear button for clear the selected item-->
   <Button
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="Clear"
       android:id="@+id/clear"
       android:textSize="20dp"
       android:textStyle="bold"
       android:layout_marginTop="200dp"
       android:layout_marginLeft="20dp"
       />
 
</RelativeLayout>

package com.example.radioapp;
 
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
   private RadioGroup radioGroup;
   Button submit, clear;
 
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       submit = (Button)findViewById(R.id.submit);
       clear = (Button)findViewById(R.id.clear);
       radioGroup = (RadioGroup)findViewById(R.id.groupradio);
 
       // Uncheck or reset the radio buttons initially
       radioGroup.clearCheck();
 
       // Add the Listener to the RadioGroup
       radioGroup.setOnCheckedChangeListener(
               new RadioGroup
                       .OnCheckedChangeListener() {
                   @Override
 
                   // The flow will come here when
                   // any of the radio buttons in the radioGroup
                   // has been clicked
 
                   // Check which radio button has been clicked
                   public void onCheckedChanged(RadioGroup group,
                                                int checkedId)
                   {
 
                       // Get the selected Radio Button
                       RadioButton
                               radioButton
                               = (RadioButton)group
                               .findViewById(checkedId);
                   }
               });
 
       // Add the Listener to the Submit Button
       submit.setOnClickListener(new View.OnClickListener() {
 
           @Override
           public void onClick(View v)
           {
 
               // When submit button is clicked,
               // Ge the Radio Button which is set
               // If no Radio Button is set, -1 will be returned
               int selectedId = radioGroup.getCheckedRadioButtonId();
               if (selectedId == -1) {
                   Toast.makeText(MainActivity.this,
                           "No answer has been selected",
                           Toast.LENGTH_SHORT)
                           .show();
               }
               else {
 
                   RadioButton radioButton
                           = (RadioButton)radioGroup
                           .findViewById(selectedId);
 
                   // Now display the value of selected item
                   // by the Toast message
                   Toast.makeText(MainActivity.this,
                           radioButton.getText(),
                           Toast.LENGTH_SHORT)
                           .show();
               }
           }
       });
 
       // Add the Listener to the Submit Button
       clear.setOnClickListener(new View.OnClickListener() {
 
           @Override
           public void onClick(View v)
           {
 
               // Clear RadioGroup
               // i.e. reset all the Radio Buttons
               radioGroup.clearCheck();
           }
       });
   }
}