code: public static int getColorWithAlpha(float alpha, int baseColor) {
          int a = Math.min(255, Math.max(0, (int) (alpha * 255))) << 24;
          int rgb = 0x00ffffff & baseColor;
          return a + rgb;
      }
docs: Create a color integer value with specified alpha.
  <p>This may be useful to change alpha value of background color.</p>
  
  @param alpha     Alpha value from 0.0f to 1.0f.
  @param baseColor Base color. alpha value will be ignored.
  @return A color with alpha made from base color.