How to add radio button list in alert dialog?

This example demonstrate about how to add radio button list in alert dialog
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
   android:layout_width = "match_parent"
   android:gravity = "center"
   android:layout_height = "match_parent">
   <TextView
      android:id = "@+id/click"
      android:layout_width = "wrap_content"
      android:textSize = "30sp"
      android:layout_height = "wrap_content"
      android:text = "Click"/>
</LinearLayout>
In the above code, we have taken text view.
Step 3 − Add the following code to src/MainActivity.java
package com.example.myapplication;
import android.annotation.TargetApi;
import android.content.DialogInterface;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Switch;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
   TextView text;
   @TargetApi(Build.VERSION_CODES.LOLLIPOP)
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      text = findViewById(R.id.click);
      text.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            showAlertDialog();
         }
      });
   }
   private void showAlertDialog() {
      AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this);
      alertDialog.setTitle("AlertDialog");
      String[] items = {"java","android","Data Structures","HTML","CSS"};
      int checkedItem = 1;
      alertDialog.setSingleChoiceItems(items, checkedItem, new DialogInterface.OnClickListener() {
         @Override
         public void onClick(DialogInterface dialog, int which) {
            switch (which) {
               case 0:
                  Toast.makeText(MainActivity.this, "Clicked on java", Toast.LENGTH_LONG).show();
               break;
               case 1:
                  Toast.makeText(MainActivity.this, "Clicked on android", Toast.LENGTH_LONG).show();
               break;
               case 2:
                  Toast.makeText(MainActivity.this, "Clicked on Data Structures", Toast.LENGTH_LONG).show();
               break;
               case 3:
                  Toast.makeText(MainActivity.this, "Clicked on HTML", Toast.LENGTH_LONG).show();
               break;
               case 4:
                  Toast.makeText(MainActivity.this, "Clicked on CSS", Toast.LENGTH_LONG).show();
               break;
            }
         }
      });
      AlertDialog alert = alertDialog.create();
      alert.setCanceledOnTouchOutside(false);
      alert.show();
   }
}
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –
Now click on textview to open Alert Dialog.