Multilingual URLs in Sitemap.xml for SXA 1.5

Question

I am having a Sitecore SXA (1.5) instance site which has multiple language for each country. For example:

www.mysite.be/fr-BE (Country: Belgium, Lang: French)

www.mysite.be/nl-BE (Country: Belgium, Lang: Dutch)

But the sitemap.xml shows only urls which have the default language setup without any language id in the URL

Example here is my sitemap.xml output:

<url>
<loc>www.mysite.be/onze-producten</loc>
<lastmod>2018-12-12</lastmod>
<changefreq>Daily</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://www.mysite.be/over-merk</loc>
<lastmod>2018-12-12</lastmod>
<changefreq>Daily</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>https://www.mysite.be/contacteer-ons</loc>
<lastmod>2018-12-11</lastmod>
<changefreq>Daily</changefreq>
<priority>0.5</priority>
</url>

But it doesn't shows pages related to French language. For example:

www.mysite.be/fr-be/contactez-nous

www.mysite.be/fr-be/faq

If this is a custom implementation, please guide.

EDIT:

As per the answer below I tried making this to work, but no luck:

public class CustomSiteMap : SitemapGenerator
    {
        protected override StringBuilder BuildSitemap(IEnumerable<Item> childrenTree, SitemapLinkOptions options)
        {
            var items = LanguageSitemap.GetSitemapItems();// gets all items below Home node
            var xDocument = LanguageSitemap.Generate(items); // generates sitemap xml with hreflang and language specific urls
            return new StringBuilder(xDocument.ToString());
        }
    }

Answer 1

SXA supports multiple languages Sitemap from SXA 1.6- check the release notes here for more details-

The SEO Sitemaps aggregate all the available sites under a single hostname, and support multiple languages  494598  9788

In your case you can customized the Sitemap XML generator for your SXA version, follow the below steps:

1) Create a new class that inherits from SitemapGenerator

2) Override BuildSitemap() method- Here you can write your own code/business logic and generate the customized sitemap.xml to support multiple languages.

I hope this helps to give you a starting point.