Adjust screen brightness in android

In this tutorial i show you,how to adjust screen brightness programatically in android.In this example we learn get current screen brightness state and changing screen brightness.

CREATE NEW ANDROID PROJECT

Step 1: Write code into activity_main.xml

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:text="Slide seekbar to change the brightness" />

    <TextView
        android:id="@+id/txtPercentage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:text="0%"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <SeekBar
        android:id="@+id/brightbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp" />


</LinearLayout>

Step 2: Write code into MainActivity.java

package dev.Androidapplink.setscreenbrightnessapp;

import dev.Androidapplink.setscreenbrightnessapp.R;

import android.app.Activity;
import android.content.ContentResolver;
import android.os.Bundle;
import android.provider.Settings.System;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager.LayoutParams;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;

public class MainActivity extends Activity {


//Seek bar object
private SeekBar brightbar;

//Variable to store brightness value
private int brightness;

//handle to the system's settings
private ContentResolver cResolver;

//Window object store a reference to the current window
private Window window;

TextView txtPerc;
   

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

        //Instantiate seekbar object
brightbar = (SeekBar) findViewById(R.id.brightbar);

txtPerc = (TextView) findViewById(R.id.txtPercentage);

        //Get the content resolver
cResolver = getContentResolver();

        //Get the current window
window = getWindow();

        //Set the seekbar range between 0 and 255
brightbar.setMax(255);

        //Set the seek bar progress to 1
brightbar.setKeyProgressIncrement(1);

try {
        //Get the current system brightness state
brightness = System.getInt(cResolver, System.SCREEN_BRIGHTNESS);
float perc = (brightness /(float)255)*100;
txtPerc.setText((int)perc + "%");
} catch (Exception e) {
// TODO: handle exception
        //Throw an error case it couldn't be retrieved
Log.e("Error", "cannot access system brightness.");
e.printStackTrace();
}

//Set the progress of the seek bar based on the system's brightness
brightbar.setProgress(brightness);


//Register OnSeekBarChangeListener, so it can actually change values
brightbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

//Set the system brightness using the brightness variable value
System.putInt(cResolver, System.SCREEN_BRIGHTNESS, brightness);
//Get the current window attributes
LayoutParams layoutpars = window.getAttributes();

//Set the brightness of this window
layoutpars.screenBrightness = brightness / (float)255;
//Apply attribute changes to this window
window.setAttributes(layoutpars);

}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

//Nothing handled here
}

@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
//Set the minimal brightness level
if(progress<=20)
{

brightness=20;
}
else //brightness is greater than 20
{
//Set brightness variable based on the progress bar 
brightness = progress;
}

//Calculate the brightness percentage
float perc = (brightness /(float)255)*100;

//Set the brightness percentage 
txtPerc.setText((int)perc + "%");

}
});
}
//IT WORK ONLY,IF SCREEN BRIGHTNESS IS NOT SETED IN "AUTO BRIGHTNESS MODE".

}