Can I buy minecoins for minecraft using an xbox card on android?

Hello! Sadly, Xbox gift cards only work on the Xbox system and applications. Now, if the android account has a linked account to your Xbox account (Meaning account information from your Xbox One is linked to your android version), then it should work.
You can also find more information
here too if you need a more detailed answer.

You can renew the xbox card onto your microsoft account, and than purchase the minecoins within the app using your microsoft account.

Hello Habuchi,

If you would like to buy minecoins with a xbox gift card it would have to be on xbox. I’m not so sure there is way you could buy it from your phone, try getting a gift card for whatever playstore you have for your device.

hi Ricardo, we purchased the Minecoin gift cards from Target - we've never had issues with these before though. they are Microsoft branded: "Minecraft Minecoins, 3500 In-Game Currency, Buy skins, textures, & worlds, Android | iOS | Nintendo Switch | Xbox One | Win 10, Minecraft Minecoins Pack - 3500 coins" we bought three separate cards and our Target receipt shows three distinct download codes on the receipt. we've never had this issue before. if we can't redeem them, we can't get his birthday money back as they are not refundable. : (

Hello @hobbes_child! I hope that you are doing well!

To answer your question, the Minecoins should be visible in Android Minecraft Bedrock Edition app as Minecoins and Marketplace content are available on Android, Amazon Kindle Fire, Amazon Fire TV, iOS (iPhone and iPad), Nintendo Switch, Windows 10, Windows 10 Mobile, and Xbox One and Series X|S.

For further information, you can check Minecraft Marketplace FAQ.