[SOLVED] Should full backup content xml file be empty or not added at all to include all?

Should full backup content xml file be empty or not added at all to include all?

So I was adding some stuff to my application manifest and I saw that I had a warning on my application tag:

On SDK version 23 and up, your app data will be automatically backed up and restored on app install. Consider adding the attribute android:fullBackupContent to specify an @xml resource which configures which files to backup.

And then I searched up for that. Apparently there are only 2 tags for that: <include> and <exclude>. I don't want to exclude any files from the backup as I don't have any local-depending files, and I don't need any <include> tags as

<include>: Specifies a set of resources to back up, instead of having the system back up all data in your app by default.

When I saw that if I don't put any <include> tags, then the system will back up all data in your app by default, which is exactly what I want.

Now I have this question: should I add the backup_content.xml file, but empty as the default settings are good, or not add the file at all? (in which case Android Studio will complain)

Solution

I also struggled the same question and couldn't find an answer. So for backup all, I tried making a backup.xml file like that:

<?xml version="1.0" encoding="utf-8"?>
   <full-backup-content>

   </full-backup-content>

and it works fine.

EDIT 06/04/21

Just got an official answer from Google IssueTracker:

The answer to your question appears at the beginning of the section titled Include and exclude files: "By default, the system backs up almost all app data". In order to back up all supported data, don't include android:fullBackupContent in your manifest file.