RadioButton in Kotlin

Last Updated : 23 Jan, 2025

Android Radio Button is bi-state button which can either be checked or unchecked. Also, it’s working is same as Checkbox except that radio button can not allow to be unchecked once it was selected. Generally, we use RadioButton controls to allow users to select one option from multiple options. By default, the RadioButton in OFF (Unchecked) state but we can change the default state of RadioButton by using android:checked attribute.

Following steps to create new project:

Click on File, then New => New Project.
Then, check Include Kotlin Support and click next button.
Select minimum SDK, whatever you need.
Select Empty activity and then click finish.

Different Attributes of RadioButton Widget

XML Attributes	Description
android:id	Used to uniquely identify the control
android:gravity	Used to specify how to align the text like left, right, center, top, etc.
android:checked	Used to specify the current state of radio button
android:onClick	It’s a name of the method to invoke when the radio button clicked.
android:textSize	Used to set size of the text.
android:textColor	Used to set color of the text.
android:textStyle	Used to set style of the text. For example, bold, italic, bolditalic etc.
android:maxWidth	Used to make the view be at most this many pixels wide.
android:minWidth	Used to make the view be at least this many pixels wide.
android:background	Used to set the background of the radio button control.
android:visibility	Used to control the visibility.

Step by Step to Demonstrate Radio Button

We will follow some steps to demonstration of application using Radio Button, follow the steps mentioned below:

Step 1: Add RadioButtons in activity_main.xml file

In android, we use radio buttons inside RadioGroup to combine set of radio buttons into single group and it will make sure that user can select only button from the group of buttons.

activity_main.xml:

xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <RadioGroup
        android:id="@+id/radio_group"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#dbeceb"
        android:padding="15dp">

        <TextView
            android:id="@+id/title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Which is your favorite color?"
            android:textStyle="bold"
            android:textSize="20sp"/>

        <RadioButton
            android:id="@+id/red"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RED"
            android:onClick="radio_button_click"/>

        <RadioButton
            android:id="@+id/green"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="GREEN"
            android:onClick="radio_button_click"/>

        <RadioButton
            android:id="@+id/yellow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="YELLOW"
            android:onClick="radio_button_click"/>

        <RadioButton
            android:id="@+id/pink"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="PINK"
            android:onClick="radio_button_click"/>
    </RadioGroup>

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Get Selected Color"/>

</LinearLayout>

Here, we are trying to implement a scenario where you need to select your favorite color. So, in activity_main.xml file, we have added 4 radio buttons inside a radio group. Each button represent a color. Now, only one radio button can be selected at a time.

Layout:

Now, we will access this widget in kotlin file and show a proper message whenever a radio button is selected.

Step 2: Open MainActivity.kt file and add below code into it.

MainActivity.kt:

Java

package com.gfg.kotlinradiobutton

import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.RadioButton
import android.widget.RadioGroup
import android.widget.Toast
import androidx.activity.enableEdgeToEdge
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.ViewCompat
import androidx.core.view.WindowInsetsCompat

class MainActivity : AppCompatActivity() 
{
      // Late Initialized variables
    lateinit var radio_group: RadioGroup
    lateinit var button:Button

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

        radio_group=findViewById<RadioGroup>(R.id.radio_group)
        button=findViewById<Button>(R.id.button)

        // Get radio group selected item
        // using on checked change listener
        radio_group.setOnCheckedChangeListener(
            RadioGroup.OnCheckedChangeListener { group, checkedId ->
                val radio: RadioButton = findViewById(checkedId)
                Toast.makeText(applicationContext," On checked change :"+
                        " ${radio.text}",
                    Toast.LENGTH_SHORT).show()
            })
          
        // Get radio group selected status
        // and text using button click event
        button.setOnClickListener{
            
              // Get the checked radio button id from radio group
            var id: Int = radio_group.checkedRadioButtonId
            
            if (id!=-1){ 
              
                  // If any radio button checked from radio group
                // Get the instance of radio button using id
                val radio:RadioButton = findViewById(id)
                Toast.makeText(applicationContext,"On button click :" +
                        " ${radio.text}",
                    Toast.LENGTH_SHORT).show()
            }else{
                
                  // If no radio button checked in this radio group
                Toast.makeText(applicationContext,"On button click :" +
                        " nothing selected",
                    Toast.LENGTH_SHORT).show()
            }
        }
    }
    
      // Get the selected radio button text 
      // using radio button on click listener
    fun radio_button_click(view: View)
    {
        // Get the clicked radio button instance
        val radio: RadioButton = findViewById(radio_group.checkedRadioButtonId)
        Toast.makeText(applicationContext,"On click : ${radio.text}",
            Toast.LENGTH_SHORT).show()
    }
}

In MainActivity.kt file, we have accessed radio group in which I have added four radio buttons. Then, we have set a listener to display toast message whenever radio button selection changes. Since AndroidManifest.xml file is very important in any android application, we are also going to mention it here.

Run as Emulator: (Two Cases are shown selecting the element and clicking the button)

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Article Tags :

RadioButton in Kotlin

Different Attributes of RadioButton Widget

Step by Step to Demonstrate Radio Button

Step 1: Add RadioButtons in activity_main.xml file

activity_main.xml:

Layout:

Step 2: Open MainActivity.kt file and add below code into it.

MainActivity.kt:

Run as Emulator: (Two Cases are shown selecting the element and clicking the button)

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