Android怎样控制评价小星星的显示（能获取到星星的个数）

代码中： mRatingBar.setRating(3.8f);
代码：

package com.example.sj.xiaoxingxing2;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.widget.RatingBar;
import android.widget.TextView;

public class MainActivity extends Activity {

    private Context context;
    private RatingBar mRatingBar ;
    private TextView mRatingBarLevel ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
//        context = this;
        mRatingBar  = (RatingBar)findViewById(R.id.service_grade_ratingBar);//星
        mRatingBarLevel = (TextView)findViewById(R.id.service_grade_level);//星个数
        mRatingBar.setRating(3.8f);
//        mRatingBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
//            @Override
//            public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
//                float i =  mRatingBar.getRating();
//                mRatingBarLevel.setText(i + "");
//            }
//        });
    }

}

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.sj.xiaoxingxing2.MainActivity">

    <!-- 星级评分条 -->
    <RatingBar
        android:id="@+id/service_grade_ratingBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:isIndicator="true"

        android:numStars="5"
        android:rating="1.5" />
    <TextView
        android:id="@+id/service_grade_level"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>



</RelativeLayout>