dropbox - How do I open a text file of any extension in Android?

I have several types of file on my Google Drive and on my SD card (.C, .ASM, .H, .INC, .LOG) which are all just text files. But I just can't view them on my Android phone because it says that there are no programs assigned to that file type. Dropbox would do fine if I could just assign it to open these extensions. So, my questions are:

1. 
   

   Is there a way to assign any extension I want to Dropbox?

   
   



2. 
   

   Is there a text viewer that will let me do that?

   
   

I tried so many, but none seem to do it. Only this HEX editor https://play.google.com/store/apps/details?id=tuba.tools seem to do it, but it won't allow me to view as a text file. Only in a split HEX/TEXT screen.