Editor 
Android simple generic text editor. The app is available from F-Droid and here
This is a fairly simple generic text editor which may be used standalone or to show or edit any sort of text file from another app. If you select a text file in a file manager or similar app you will be offered the option of using this editor along with whatever other apps you have installed that can show or edit a text file. Files will initially be opened read only, long touch on the display or touch the edit item in the toolbar to enable editing.
There are five toolbar items which may appear:
And on the menu:
Edit the current read only text.
View the current file read only.
Save the current file if modified.
Start a new empty file. Use the Save as item to save the new file.
Choose a file to open from the chooser dialog that pops up. The parent folder will be the first in the list. See File Chooser. The file will initially be read-only. Touch the Edit toolbar item to enable editing.
Choose a file from the list that pops up. As above the file will initially be read only. The last entry, Clear list, will clear the list.
Enter a new file name in the dialog that pops up. Absolute names
starting with a slash '/' will be saved in that exact path if
possible. Names without a starting slash will be saved relative to the
main public folder, /sdcard/, or /storage/emulated/0/.
Enter search text in the field that pops up in the toolbar. The first matching item will be highlighted. Use the search button in the keyboard for find next. The exact regular expression syntax used is in the android documentation for Pattern.
You may find all recent files that contain the current search text. This menu item will only appear while the search widget is active. A dialog will pop up with a list of matching files. Touch an entry to open that file. You may repeat this or refine the search text to find the desired file.
You will be prompted to choose a viewer for an html file containing the encoded markdown from the current open file. If the text contains no markdown the result will be the same text.
If the current open file is a C, C++, Objective C, Go, Java, Javascript, Python, Shell script, Swift, CSS, HTML or Markdown file, the keywords, classes comments, strings, etc will be highlighted. See Syntax Highlighting.
If a line of text is found within the first or last two or three lines of the file which matches the mode line pattern, the mode of the editor will be changed after the file is loaded. See Mode line.
# ed: [[no]vw] [[no]ww] [[no]sg] [[no]hs] [th:l|d|r] [ts:l|m|s] [tf:m|p]If the file being edited is not a plain text file, selections created by double tapping or long touching on the text will be extended to enclosing delimiters (brackets, quotes) on the same text line.
If you touch the new, back or open button, and the current file has been modified, you will be prompted whether you want to save it, else the editor will just exit or open a file chooser. The current file may be saved on app pause using the menu option. The scroll position and name will be remembered for the last 10 files opened.
If a file has changed in storage while it was open in the editor, if you attempt to save it, or the app is resumed, you will be prompted whether to overwrite or reload the file.
If there is no open file any text entered will by default be saved in
Documents/Editor.txt. This file will be loaded on start if it
exists. Use the Save as menu item to save it elsewhere.
Text files opened or shared by another app may be viewed and
edited. Some apps may share files or text using a content URI that
is not resolvable to a path to a file in storage. In that case the
editor will read the file into the default file. The default file in
storage will not be overwritten unless the file is saved. Use the
Save as menu item to save the file elsewhere.