How to change screen brightness programmatically in android?

This example demonstrates how do I change screen brightness programmatically 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"?>
<LinearLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:padding="8dp"
   android:gravity="center"
   android:orientation="vertical"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Turn Off Screen"/>
   <SeekBar
      android:id="@+id/seekBar"
      android:layout_marginTop="10dp"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" />
</LinearLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.content.Context;
import android.provider.Settings;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.SeekBar;
public class MainActivity extends AppCompatActivity {
   SeekBar lightBar;
   Context context;
   int brightness;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      lightBar = findViewById(R.id.seekBar);
      context = getApplicationContext();
      brightness =
         Settings.System.getInt(context.getContentResolver(),
         Settings.System.SCREEN_BRIGHTNESS, 0);
      lightBar.setProgress(brightness);
      lightBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
         @Override
         public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            Settings.System.putInt(context.getContentResolver(),
               Settings.System.SCREEN_BRIGHTNESS, progress);
         }
         @Override
         public void onStartTrackingTouch(SeekBar seekBar) { }
         @Override
         public void onStopTrackingTouch(SeekBar seekBar) { }
      });
   }
}
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"
   xmlns:tools="http://schemas.android.com/tools"
   package="app.com.sample">
   <uses-permission
      android:name="android.permission.WRITE_SETTINGS"
      tools:ignore="ProtectedPermissions" />
   <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 −