图片透明度。。RatingBar

------------------------------main.java-------------------------

package org.crazyit.ratingbar;


import android.app.Activity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.RatingBar.OnRatingBarChangeListener;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;


/**
 * Description:
 * <br/>site: <a href="http://www.crazyit.org">crazyit.org</a> 
 * <br/>Copyright (C), 2001-2012, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee [e-mail]
 * @version  1.0
 */
public class RatingBarTest extends Activity
{
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final ImageView image = (ImageView)findViewById(R.id.image);
RatingBar ratingBar = (RatingBar)findViewById(R.id.rating);

ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener()
{
//当拖动条的滑块位置发生改变时触发该方法
@Override
public void onRatingChanged(RatingBar arg0
, float rating, boolean fromUser)
{
//动态改变图片的透明度，其中255是星级评分条的最大值，
//5个星星就代表最大值255
image.setAlpha((int)(rating * 255 / 5));
}
});
}
}

---------------------------------main.xml------------------------------------------

<?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"
>
<ImageView 
android:id="@+id/image"
android:layout_width="fill_parent" 
android:layout_height="240px" 
android:src="@drawable/lijiang"
/>
<!-- 定义一个星级评分条 -->
<RatingBar 
android:id="@+id/rating"
android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:numStars="5"
android:max="255"
android:progress="255"
android:stepSize="0.5"
/>
</LinearLayout>