How to control the height and width of the default alert dialog in android?

This example demonstrates how do I control the height and width of the default alert dialog in android.

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:layout_width="match_parent"
   android:layout_height="match_parent"
   android:id="@+id/relativeLayout"
   tools:context=".MainActivity">
   <Button
      android:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Show Alert Dialog"
      android:layout_centerInParent="true" />
</RelativeLayout>

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

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.RelativeLayout;
   public class MainActivity extends AppCompatActivity{
      Button button;
      RelativeLayout relativeLayout;
      Context context;
      Activity myActivity;
      @Override
      public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         relativeLayout = findViewById(R.id.relativeLayout);
         context = getApplicationContext();
         button = findViewById(R.id.button);
         myActivity = MainActivity.this;
         button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
            AlertDialog.Builder builder = new AlertDialog.Builder(myActivity);
            builder.setTitle("My Action Bar");
            builder.setMessage("This is my custom Action bar, do you like it?");
            builder.setPositiveButton("Yes", null);
            builder.setNegativeButton("No", null);
            AlertDialog alertDialog = builder.create();
            alertDialog.show();
            WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams();
            layoutParams.copyFrom(alertDialog.getWindow().getAttributes());
            layoutParams.width = WindowManager.LayoutParams.MATCH_PARENT;
            layoutParams.height = WindowManager.LayoutParams.MATCH_PARENT;
            alertDialog.getWindow().setAttributes(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="app.com.sample">
   <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  Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –