I also want to filter the status bar.

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"tools:context=".MainActivity">

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="add Filter"
    android: id="@+id/ButtonAddFilter"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Remove Filter"
    android: id="@+id/ButtonRemoveFilter"
    android:layout_alignParentTop="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"/>
</RelativeLayout>

public class MainActivity extensions Activity {

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

    Button ButtonAddFilter= (Button) findViewById (R.id.ButtonAddFilter);
    buttonAddFilter.setOnClickListener(newView.OnClickListener(){
        @ Override
        public void onClick (View v) {
            Intent = new Intent (MainActivity.this, FilterService.class);
            startService(intent);
        }
    });

    Button ButtonRemoveFilter= (Button) findViewById (R.id.ButtonRemoveFilter);
    buttonRemoveFilter.setOnClickListener(newView.OnClickListener(){
        @ Override
        public void onClick (View v) {
            Intent = new Intent (MainActivity.this, FilterService.class);
            stopService(intent);
        }
    });
}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

</LinearLayout>

public class FilterService extensions Service {

private View mView;
private WindowManager mWindowManager;

@ Override
public int onStartCommand(Intent intint, int flags, int startId) {

    LayoutInflater layoutInflater=LayoutInflater.from(this);

    WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,    
            WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
            PixelFormat.TRANSLUCENT                       
    );

    mWindowManager=(WindowManager) getSystemService(Context.WINDOW_SERVICE);

    mView = layoutInflater.inflate(R.layout.filter, null);

    mView.setBackgroundColor(Color.argb(80,0,0));

    mWindowManager.addView (mView, layoutParams);

    return START_NOT_STICKY;
}

@ Override
public void onDestroy() {
    super.onDestroy();
    mWindowManager.removeView(mView);
}

@ Nullable
@ Override
public IBinder onBind (Intent int) {
    return null;
}
}