Change the System Brightness Programmatically

You can use following:

// Variable to store brightness value
private int brightness;
// Content resolver used as a handle to the system's settings
private ContentResolver cResolver;
// Window object, that will store a reference to the current window
private Window window;

In your onCreate write:

// Get the content resolver
cResolver = getContentResolver();
 
// Get the current window
window = getWindow();
    
try {
    // To handle the auto
    Settings.System.putInt(
        cResolver,
        Settings.System.SCREEN_BRIGHTNESS_MODE,
        Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL
    );
    // Get the current system brightness
    brightness = Settings.System.getInt(
        cResolver, Settings.System.SCREEN_BRIGHTNESS
    );
} catch (SettingNotFoundException e) {
    // Throw an error case it couldn't be retrieved
    Log.e("Error", "Cannot access system brightness");
    e.printStackTrace();
}

Write the code to monitor the change in brightness.

then you can set the updated brightness as follows:

// Set the system brightness using the brightness variable value
Settings.System.putInt(
    cResolver, Settings.System.SCREEN_BRIGHTNESS, brightness
);
// Get the current window attributes
LayoutParams layoutpars = window.getAttributes();
// Set the brightness of this window
layoutpars.screenBrightness = brightness / 255f;
// Apply attribute changes to this window
window.setAttributes(layoutpars);

Permission in manifest:

<uses-permission android:name="android.permission.WRITE_SETTINGS" />

For API >= 23, you need to request the permission through Settings Activity, described here: Can't get WRITE_SETTINGS permission

I had the same problem.

Two solutions:

here, brightness =(int) 0 to 100 range as i am using progressbar

1 SOLUTION

float brightness = brightness / (float)255;
WindowManager.LayoutParams lp = getWindow().getAttributes();
        lp.screenBrightness = brightness;
        getWindow().setAttributes(lp);

2 SOLUTION

I just used dummy activity to call when my progress bar stop seeking.

 Intent intent = new Intent(getBaseContext(), DummyBrightnessActivity.class);
                    Log.d("brightend", String.valueOf(brightness / (float)255));
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); //this is important
                    //in the next line 'brightness' should be a float number between 0.0 and 1.0
                    intent.putExtra("brightness value", brightness / (float)255); 
                    getApplication().startActivity(intent);

Now coming to the DummyBrightnessActivity.class

 public class DummyBrightnessActivity extends Activity{

private static final int DELAYED_MESSAGE = 1;

private Handler handler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);            
    handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            if(msg.what == DELAYED_MESSAGE) {
                DummyBrightnessActivity.this.finish();
            }
            super.handleMessage(msg);
        }
    };
    Intent brightnessIntent = this.getIntent();
    float brightness = brightnessIntent.getFloatExtra("brightness value", 0);
    WindowManager.LayoutParams lp = getWindow().getAttributes();
    lp.screenBrightness = brightness;
    getWindow().setAttributes(lp);

    Message message = handler.obtainMessage(DELAYED_MESSAGE);
    //this next line is very important, you need to finish your activity with slight delay
    handler.sendMessageDelayed(message,200); 
}

}

don't forget to register DummyBrightnessActivity to manifest.

hope it helps!!