安卓学习第23课——ratingBar

<LinearLayout 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:orientation="vertical">
  <ImageView
        android:id="@+id/image"
        android:layout_width="match_parent"
        android:layout_height="240dp"
        android:src="@drawable/lijiang" />
    <RatingBar
        android:id="@+id/ratingBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:numStars="5"
        android:progress="255"
        android:stepSize="0.5" />
</LinearLayout>

package com.example.ratingbar;

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

public class MainActivity extends Activity {

    ImageView image;
    RatingBar ratingBar;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        image=(ImageView) findViewById(R.id.image);
        ratingBar=(RatingBar) findViewById(R.id.ratingBar);
        ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener(){

            @Override
            public void onRatingChanged(RatingBar ratingBar, float rating,
                    boolean fromUser) {
                image.setImageAlpha((int) (rating*255/5));
                
            }
            
        });
    }
}