通过星级改变图片的透明度

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<ImageView
android:id="@+id/imageview"
android:layout_width="match_parent"
android:layout_height="320dp"
android:src="@drawable/lijiang"/>
<RatingBar
android:id="@+id/ratingbar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:numStars="5"
android:max="255"
android:progress="255"
android:stepSize="0.5" />

</LinearLayout>

MainActivity.java

<pre name="code" class="java">package com.lxm.ratingbartest;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.RatingBar.OnRatingBarChangeListener;

public class MainActivity extends Activity {
RatingBar ratingbar;
ImageView image;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
image = (ImageView) findViewById(R.id.imageview);
ratingbar = (RatingBar) findViewById(R.id.ratingbar);
ratingbar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() {

@Override
public void onRatingChanged(RatingBar ratingBar, float rating,
boolean fromUser) {
image.setAlpha((int)(rating*25/5));
}
});
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}

运行效果：