

--------------------------------------------
activity_main.xml
---------------------------------------------

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="20dp"
    android:gravity="center_horizontal">

    <!-- Default Radio Group -->
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Default Radio Group"
        android:textSize="18sp"
        android:textStyle="bold"
        android:layout_marginBottom="10dp" />

    <RadioGroup
        android:id="@+id/defaultRadioGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <RadioButton
            android:id="@+id/defaultRadio1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Option 1"
            android:checked="true" />

        <RadioButton
            android:id="@+id/defaultRadio2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Option 2" />
    </RadioGroup>

    <!-- Custom Radio Group -->
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Custom Radio Group"
        android:textSize="18sp"
        android:textStyle="bold"
        android:layout_marginTop="30dp"
        android:layout_marginBottom="10dp" />

    <RadioGroup
        android:id="@+id/customRadioGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <RadioButton
            android:id="@+id/customRadio1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Custom 1"
            android:button="@drawable/ic_baseline_add_reaction_24" />

        <RadioButton
            android:id="@+id/customRadio2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Custom 2"
            android:button="@drawable/ic_baseline_add_reaction_24" />
    </RadioGroup>

    <!-- Button to Show Selected Option -->
    <Button
        android:id="@+id/showButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="SHOW SELECTED"
        android:layout_marginTop="20dp" />
</LinearLayout>

=====================================================================
MainActivity.kt
=====================================================================


import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.widget.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val defaultGroup = findViewById<RadioGroup>(R.id.defaultRadioGroup)
        val customGroup = findViewById<RadioGroup>(R.id.customRadioGroup)
        val showButton = findViewById<Button>(R.id.showButton)

        showButton.setOnClickListener {
            val defaultSelectedId = defaultGroup.checkedRadioButtonId
            val customSelectedId = customGroup.checkedRadioButtonId

            val defaultRadio = findViewById<RadioButton>(defaultSelectedId)
            val customRadio = findViewById<RadioButton>(customSelectedId)

            val result = "Default: ${defaultRadio.text}\nCustom: ${customRadio.text}"
            Toast.makeText(this, result, Toast.LENGTH_LONG).show()
        }
    }
}


==============================
drawable-->right click-->vector asset-->select image and check the size
