How to decrease brightness like screen filter

Question

I have been trying to create a simple app like this but I failed. What should I do based on this answer? The code I use:

MainActivity.java

public class MainActivity extends Activity  { 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_main);
        SeekBar fseekbar = (SeekBar) findViewById(R.id.fseekBar2);
        fseekbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener(){

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress,
        boolean fromUser) {
        // TODO Auto-generated method stub

    }

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

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

My relative Layout.xml

<LinearLayout
        android:id="@+id/linear"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

  <SeekBar
        android:id="@+id/fseekBar2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />

</LinearLayout>

The problem is that I cannot create a window manager and set to layoutParams the value of the brightness.

Answer 1

Try this...

MainActivity.java

public class MainActivity extends Activity {
private SeekBar brightbar;

//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;

TextView txtPerc;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.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
        brightness = System.getInt(cResolver, System.SCREEN_BRIGHTNESS);
    }
    catch (SettingNotFoundException e)
    {
        //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()
    {
        public void onStopTrackingTouch(SeekBar seekBar)
        {
            //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);
        }

        public void onStartTrackingTouch(SeekBar seekBar)
        {
            //Nothing handled here
        }

        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser)
        {
            //Set the minimal brightness level
            //if seek bar is 20 or any value below
            if(progress<=20)
            {
                //Set the brightness to 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 +" %");
        }
    });   
}
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Slide the bar to change the brightness:"
    android:id="@+id/txtPercentage" />

<SeekBar
    android:id="@+id/brightbar"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="30dip"
    android:layout_marginRight="30dip" >
</SeekBar>

</LinearLayout>

Happy coding...