Android Question Find and Open a Text File

I need to implement a function where the user can find a TXT file on the device (which can be in the internal or external storage) and the application can open it. Looking on the forum I found several examples that allow reading the TXT file, however, I didn't find an example that gives the user the opportunity to indicate which text file he wants to open. I'm new on B4A programming and I'm having a hard time dealing with the file system.

Could someone help me with some practical and simpler example? Preferably with pure B4A...