code: @Nullable
      public static Drawable getDrawable(Context context, @AttrRes int attrId) {
          Drawable d = null;
          TypedArray a = context.obtainStyledAttributes(new int[]{attrId});
          try {
              d = a.getDrawable(0);
          } catch (UnsupportedOperationException e) {
              error("drawable", attrId, e);
          }
          a.recycle();
          return d;
      }
docs: Get the Drawable specified by the attribute in the Context's theme.
  
  @return null if the drawable does not exist
  @since 4.0.0