Method _setActiveOption

src/material/list/selection-list.ts:457–460

* Sets an option as active. * @param index Index of the active option. If set to -1, no option will be active.

(index: number)

   * @param index Index of the active option. If set to -1, no option will be active.
   */
  private _setActiveOption(index: number) {
    this._items.forEach((item, itemIndex) => item._setTabindex(itemIndex === index ? 0 : -1));
    this._keyManager.updateActiveItem(index);
  }

  /**
   * Resets the active option. When the list is disabled, remove all options from to the tab order.