I perfectly use the AutoCompleteEditText_ TextChanged to catch the first 3 characters in a filename with a part of the code "If New = St.substring2(0,3) Then.......etc.
But what I have also to catch characters in the middle or end of a filename?
You do not need to use TextChanged with AutoCompleteEditText. It should work automatically.
However it only works with the prefix. You should use a database if you want to find matches that do not start at the beginning. Another option is to build a small index.