Transfer Android app with offline data to NEW PHONE without ROOT

Question

I've purchased a new phone and have transferred most of the data from the old device to the new one using various means.

There is one app, however, that does not have account login, so I cannot save cached data in the cloud. Meaning that I have no choice but to move/restore the app to the new device with the offline (cached) data.

This app is quite important to me, and I need the offline data.

I know of the following techniques to do this:

• Backup and restore app + cached data using Helium: copy & replace the 'sdcard/carbon' folder from the old phone to the new phone. After doing this, restore the app with data on the new phone.
• Root the device and use Titanium backup to do the same.
• Backup apps using the 'Backup' feature in Google Drive.

Helium just did not work (with a brand new phone with Android 8.0!).

I cannot use Titanium as I cannot root my old phone at this point (before backup is complete). And restoring the app this way will in all likelihood require that I root my new phone as well, which is a deal-breaker.

Does Google Drive Backup work with all third party apps? I did not see the app I want to save in the list of apps whose data was being saved by Google Drive.

What should I do? Can anyone advise?

EDIT:

All of the techniques given on various sites for both partial and full backups (including nandroid backups) are device specific, i.e. you can restore to the same device only, not from one device to another. This includes both Droid Explorer and Simple ADB Backup too, apparently.

Is there no general way of restoring an app with data to a new phone without root? Google Drive backup does this without root. If it can do that, why can't other apps?

Also, various people suggested using MyBackup Pro / Android Assistant / DrFone+. All these tools give up before even trying: they all seem to require root.

Answer 1

You can use adb backup. You can specify the package name for backup a single app (for comprehensive details refer to Nikolay Elenkov)

adb backup [-f <file>] [-apk|-noapk] [-obb|-noobb] [-shared|-noshared] [-all] [-system|nosystem] [-keyvalue|-nokeyvalue] [<packages...>]
adb restore <file>

Note: some apps won't allow adb backup. even if adb backup is allowed, cache is not included.

Find a [GUIDE] How to enable adb backup for any app, decompile, recompile and sign the apk, where you have set the following flags:

android:allowBackup="true"
android:fullBackupOnly="false"

On the source phone, update the apk with your modified one. To do this without uninstalling, this may require to increment the android:versionCode in AndroidManifest.xml, and you must sign the apk using the same original signature that was used previously for the apk from the Play Store. This is the pitfall if you are not the author of the app it is not possible. However, if you manage this the install will succeed without data loss. Otherwise install will be rejected. (You still have the option to set allowBackup directly on rooted phone, but this may be out of scope because with root you can backup app directly) apparently there is no way to override AndroidManifest.xml during runtime

Once you have installed the modified apk you can make a backup of your app from source phone, and restore it to destination phone without root.

Install the latest Platform Tools and run from cmd.exe as Administrator:

adb.exe backup "-f C:\example.ab -apk -obb com.example.package"

---

edit:

• be aware you have compiled a different app that can't be updated via PlayStore anymore

• starting with api level 30 modified apk is no longer required as the flag seems ignored
  xda-developers.com

• starting with api level 31 the flag is different

  android:debuggable="true"