What do we need?
- A rooted Android phone
- Titanium Backup
- SQLite Editor
Any other similar app should also do the trick. Before changing your phone, ROM or whatever, you need to create a backup of the LINE app, so we have the saved data of the app before doing anything.
How to restore
- Do a fresh install of LINE from the App Store, but don't open it right away.
- Restore LINE app data from the Titanium Backup backup.
- Open SQLite Editor and in the apps tab select LINE app.
- SQLite should open the app and show you the available .db files, select naver_line
- You should now see all the tables inside that .db file, select setting
- Once you're inside the table, seeing all the data it contains, select Menu > Delete All
- Open LINE app and login with your username
- You will receive a pop-up telling that the previous account will be deleted along with the chat history. Just click OK.
- Follow the rest of the setup process
- Once finished, you should be able to see all your saved chat history.
And that is, we now have our restored data in LINE.
If the above doesn't work for you, there's another way to do it with SQLite Manager
Update: Another way to do it
- As before, do a previous backup.
- Restore your backup on your new phone or ROM
- Use a root file explorer to go to /data/data/jp.naver.line.android/databases
- Copy naver_line to your PC and rename it as naver_line_old
- Do a fresh install and do the whole setup process
- Again use a root explorer to get the new version of naver_line and save it as naver_line_new on your PC
- In your PC, open naver_line_old and export chat_history table to a file.
- In your PC, open naver_line_new and import the exported file.
- Copy naver_line_new to /data/data/jp.naver.line.android/databases/naver_line
- Restart your phone.
With these steps, you should have all your chat history restored, but it won't be visible until the people in your chat conversations message you again.