title: Change (only) the color of RatingBar
body: <p>I'm trying to change the stars color to yellow.<br>
  I don't want to use another style(!), just changing the color of the built-in stars in the RatingBar.</p>
  
  <p>I've read a few tutorials how to change the style, they are all pretty similar.   But for some reason it just doesn't work for me.<br>
  Anyway, since I just want to change the color, and not the whole style, I used the code below:</p>
  
  <pre><code>@Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_details);
          rbBookRating = (RatingBar) findViewById(R.id.rbRating);
          rbBookRating.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
              @Override
              public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
  
              }
          });
          LayerDrawable stars = (LayerDrawable) rbBookRating.getProgressDrawable();
          stars.getDrawable(2).setColorFilter(Color.YELLOW, PorterDuff.Mode.SRC_ATOP);
          stars.getDrawable(1).setColorFilter(Color.CYAN, PorterDuff.Mode.SRC_ATOP);
          stars.getDrawable(0).setColorFilter(Color.RED, PorterDuff.Mode.SRC_ATOP);
      }
  </code></pre>
  
  <p>layout</p>
  
  <pre><code>&lt;RatingBar
  android:id="@+id/rbRating"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:isIndicator="true"
  android:stepSize="0.5" /&gt;
  </code></pre>
  
  <p>(It seems that) My app crashes right after this line:</p>
  
  <pre><code>LayerDrawable stars = (LayerDrawable) rbBookRating.getProgressDrawable();
  </code></pre>
  
  <p>Any suggestion why?</p>