public void registerEnterHandler(final Runnable runnable) {
    new AnAction() {
      @Override
      public void update(@NotNull AnActionEvent e) {
        e.getPresentation().setEnabled(!myMonths.isPopupVisible() && !myDays.isPopupVisible());
      }

      @Override
      public @NotNull ActionUpdateThread getActionUpdateThread() {
        return ActionUpdateThread.EDT;
      }
      @Override
      public void actionPerformed(@NotNull AnActionEvent e) {
        runnable.run();
      }
    }.registerCustomShortcutSet(KeyEvent.VK_ENTER, 0, this);
  }
public void registerEnterHandler(final Runnable runnable)