How do I obtain the starting and ending character position in a text box that a user is highlighting?

I have a large edit box in gui that I used to display the contents of a text file to the user. The user can then highlight a number in the text and press a gui button to "record the text". If the text box tag was "eb_filetext", in versions up to matlab 2014 I used the following 3 commands to achieve this task:

begins = handles.eb_filetext_java.getSelectionStart()
    ends = handles.eb_filetext_java.getSelectionEnd()
    selection = char(handles.eb_filetext_java.getSelectedText())

Versions 2016 and up, this function is broken. These few lines of code are critical to the operation of a 15,000 line GUI that was developed. How can I replace/update this code! Help!