Change background color using Java code, setBackgroundColor()

package com.AndroidBackgroundColor;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.SeekBar;

public class AndroidBackgroundColor extends Activity {
 
 SeekBar seekRed, seekGreen, seekBlue, seekAlpha;
 View targetView;
 
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);
  
     targetView = (View)findViewById(R.id.mainlayout);
  
     seekRed = (SeekBar)findViewById(R.id.seekred);
     seekGreen = (SeekBar)findViewById(R.id.seekgreen);
     seekBlue = (SeekBar)findViewById(R.id.seekblue);
     seekAlpha = (SeekBar)findViewById(R.id.seekalpha);
  
     seekRed.setOnSeekBarChangeListener(seekChangeListener);
     seekGreen.setOnSeekBarChangeListener(seekChangeListener);
     seekBlue.setOnSeekBarChangeListener(seekChangeListener);
     seekAlpha.setOnSeekBarChangeListener(seekChangeListener);
 }

 private SeekBar.OnSeekBarChangeListener seekChangeListener
 = new SeekBar.OnSeekBarChangeListener(){

  @Override
  public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {
   // TODO Auto-generated method stub
   updateBackgroundColor();
  }

  @Override
  public void onStartTrackingTouch(SeekBar arg0) {
   // TODO Auto-generated method stub
   
  }

  @Override
  public void onStopTrackingTouch(SeekBar arg0) {
   // TODO Auto-generated method stub
   
  }};

 private void updateBackgroundColor(){
  
  int red = seekRed.getProgress();
  int green = seekGreen.getProgress();
  int blue = seekBlue.getProgress();
  int alpha = seekAlpha.getProgress();

  targetView.setBackgroundColor(
    ((alpha << 24) & 0xFF000000)
    + ((red << 16) & 0x00FF0000)
    + ((green << 8) & 0x0000FF00)
    + (blue & 0x000000FF));

 }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:id="@+id/mainlayout"
 >
<TextView
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="@string/hello"
 />
<TextView
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="RED"
 />
<SeekBar
 android:id="@+id/seekred"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:max="255"
 />
<TextView
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="GREEN"
 />
<SeekBar
 android:id="@+id/seekgreen"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:max="255"
 />
<TextView
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="BLUE"
 />
<SeekBar
 android:id="@+id/seekblue"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:max="255"
 />
<TextView
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="ALPHA"
 />
<SeekBar
 android:id="@+id/seekalpha"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:max="255"
 />
</LinearLayout>