Make the RatingBar secondary color opaque

Question

I'm trying to make the un-filled stars in the RatingBar an opaque color, but it seems like a tall task consisting of tint lists and PorterDuff Modes. Is there a rock solid way to make the un-filled stars of a RatingBar a truely opaque color?

val color = ContextCompat.getColor(context, android.R.color.white)
ratingBar.secondaryProgressTintList = ColorStateList.valueOf(white)
ratingBar.secondaryProgressTintMode = PorterDuff.Mode.OVERLAY //whats the sauce?

The un-filled color is still transparent, and the background of the view is half white!

Answer 1

The stars in a RatingBar are simply a LayerDrawable. The key to setting the color of unfilled stars is to get a handle on the index within the LayerDrawable that contains a description of the drawable for unfilled stars (index = 0). Once we have that drawable, we can color it with "Drawable#setTint()" for API 21+ or with "Drawable#setColorFilter()" for API <21.

The following example sets the unfilled stars to an opaque green:

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        RatingBar ratingBar = findViewById(R.id.ratingBar);
        LayerDrawable stars = (LayerDrawable) ratingBar.getProgressDrawable();
        int unfilledColor = getResources().getColor(android.R.color.holo_green_dark);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            stars.getDrawable(0).setTint(unfilledColor);
        } else {
            stars.getDrawable(0).setColorFilter(unfilledColor, PorterDuff.Mode.SRC_ATOP);
        }
    }
}