How to make an alert dialog fill 50% of screen size on Android devices using Kotlin?

This example demonstrates how to make an alert dialog fill 50% of screen size on Android devices 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.

<?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:background="#f2f6f4"
   android:padding="10dp"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/text2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="70dp"
      android:background="#008080"
      android:padding="5dp"
      android:text="TutorialsPoint"
      android:textColor="#fff"
      android:textSize="24sp"
      android:textStyle="bold" />
   <Button
      android:id="@+id/buttonAlert"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:text="Show Alert Dialog"/>
</RelativeLayout>

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

import android.os.Bundle
import android.util.DisplayMetrics
import android.view.WindowManager
import android.widget.Button
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   lateinit var button: Button
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      button = findViewById(R.id.buttonAlert)
      button.setOnClickListener {
         val builder: android.app.AlertDialog.Builder = android.app.AlertDialog.Builder(this)
         builder.setTitle("Say Hello!")
         builder.setMessage("Do you want to reply back?")
         builder.setPositiveButton("Yes", null)
         builder.setNegativeButton("No", null)
         val dialog: android.app.AlertDialog? = builder.create()
         dialog?.show()
         val displayMetrics = DisplayMetrics()
         windowManager.defaultDisplay.getMetrics(displayMetrics)
         val displayWidth = displayMetrics.widthPixels
         val displayHeight = displayMetrics.heightPixels
         val layoutParams = WindowManager.LayoutParams()
         layoutParams.copyFrom(dialog?.window?.attributes)
         val dialogWindowWidth = (displayWidth * 0.5f).toInt()
         val dialogWindowHeight = (displayHeight * 0.5f).toInt()
         layoutParams.width = dialogWindowWidth
         layoutParams.height = dialogWindowHeight
         dialog?.window?.attributes = layoutParams
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.q11">
   <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.