How to create a simple alert dialog with Ok and cancel buttons using Kotlin?

This example demonstrates how to create a simple alert dialog with Ok and cancel buttons using Kotlin.

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.

Example

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:id="@+id/rl"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:padding="8dp"
   tools:context=".MainActivity">
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="50dp"
      android:padding="8dp"
      android:text="Tutorials Point"
      android:textColor="@android:color/holo_green_dark"
      android:textSize="48sp"
      android:textStyle="bold" />
   <TextView
      android:id="@+id/button"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:clickable="true"
      android:focusable="true"
      android:text="Show Alert dialog"
      android:textAlignment="center" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

Example

import android.os.Bundle
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   private lateinit var textView: TextView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      textView = findViewById(R.id.button)
      textView.setOnClickListener { showAlertDialog() }
   }
   private fun showAlertDialog() {
      val alertDialog: AlertDialog.Builder = AlertDialog.Builder(this@MainActivity)
      alertDialog.setTitle("AlertDialog")
      alertDialog.setMessage("Do you wanna close this Dialog?")
      alertDialog.setPositiveButton(
         "yes"
      ) { _, _ ->
         Toast.makeText(this@MainActivity, "Alert dialog closed.", Toast.LENGTH_LONG).show()
      }
      alertDialog.setNegativeButton(
         "No"
      ) { _, _ -> }
      val alert: AlertDialog = alertDialog.create()
      alert.setCanceledOnTouchOutside(false)
      alert.show()
   }
}

Step 4 − Add the following code to androidManifest.xml

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.myapplication">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

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 the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen