Mime type for .txt files?

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http://stackoverflow.com – I´m trying to share a .txt file with share intent, if setting "text/plain" mime type, it reads the content like text not like text file, then the options given in the share menu are whatsapp, Line, etc.. anybody knows how to configure the share intent in order the share options were only the programs that are able to send a .txt file (Gmail, Dropbox, etc but not whatsapp..)? Thanks (HowTos)