code: private void setStyle(Button view) {
          final int textSize = styledAttributes.getInt(R.styleable.PinLock_keypadTextSize, 12);
          view.setTextSize(TypedValue.COMPLEX_UNIT_SP, textSize);
  
          final int color = styledAttributes.getColor(R.styleable.PinLock_keypadTextColor, Color.BLACK);
          view.setTextColor(color);
  
          final int background = styledAttributes
                  .getResourceId(R.styleable.PinLock_keypadButtonShape, R.drawable.rectangle);
          view.setBackgroundResource(background);
      }
docs: Setting Button background styles such as background, size and shape
  @param view Button itself