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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 −
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