Develop Reference

reusing Room or SQLite database in the app?

I'm trying to figure out an android app that stores user's data in a database on sdcard.
But I don't know if it's possible to have these too:
even if the user deletes the app, the db remains and the user can access it.
So later they can re-install and give the app the path to the db file. The app uses that file as a database again.
Something like WhatsApp db, but the user must have the database as a file on their phone so they can transfer and store it anywhere. The data is large so it's not a good idea to get a backup file.
Is it possible to create it with Room or SQLite? and reuse it again?

Under what circumstance will the SQLite database file got lost or destroyed?

I know that one instance where an App's SQLite file may be removed from the System is when the user uninstall the Application. Apart from this situation, under what circumstance(s) will the SQLite file get lost or be destroyed in the Android System?
Again, under what circumstance will the SQLite database file loose all it's content even if the App is not uninstalled?
Will there be an instance where the Android System does this?

Settings -> App -> Data -> Clear Data would also delete the SQL. Also rooted phone can do whatever he likes with the SQLite files.

There is no way that the Android system will erase or remove your file. Database files are stored, along with other app data, under {package_name}/data/data folder so no one except your app can touch it (ignore rooted devices).
Only the following can happen:
1. your code cleared/corrupted the db file
2. user has cleared app data from device settings

How to take Backup of Data when user uninstall app and re-install app all data recover

I am try to take backup of my sqlite database when user uninstall app. and recover that sqlite data when user Re-install app. I am try custom BackupAgentHelper but i am install app and insert data of sqlite database and then uninstall app. and reinstall app then my database is empty. If any one have solution of this issue send me source code of this

You could try saving the database to the SD Card. However, you will lose access to the database if the user changes the SD Card .
Another option would be to back it up to a server at regular intervals.

You can save data on Google drive.
Use App Folder service
https://developers.google.com/drive/web/appdata
https://developers.google.com/drive/android/appfolder

What happens if an android app, which creates database, is then uninstalled?

I developed and install an android application which create a sqlite database.
If I uninstall this app the database will be automatically dropped?

The database is a file in private storage ( /data/data/{package.name}/databases/db.file )
when you uninstall an app the /data/data/{package.name}/ is deleted, either the user associated to the app is.

YES....
After create Database it will be located at data/data/YourPackage/mydatabase.db.
when you install application on Emulator or Phone then it will be visible in File Explorer.
This mydatabase.db file will be deleted when you uninstall your application but if you reinstall this application then this database file again created and will be available in your private folder.
Edit
Suppose you want to store some value in Database(SQLite), For this you need to create one java class like MySQLiteHelper and then you can simply write your value in database.
If you uninstall you application then your value and database will be deleted but if you again reinstall your application then your database again created but previous value will be lost.

I think so, database will be dropped with all files in your app's private folder :)

Sqlite database lifecycle? It is deleted when the app is closed?

I'm following a simple tutorial that creates a class which extends from SQLiteOpenHelper and creates a DB with one table and 5 rows.
OK, but I need to understand some more about android Sqlite databases. For example, what happens if the app is closed or the phone is off? Is the database deleted?

Of course the database isn't deleted. I assume you're doing it the "proper" way. In which case the database is persistent. (of course if you choose to create a database in a temporary directory or something similar then its not going to work properly).
Think of it like this. The database is basically a text file. What you're doing to the database is modifying the contents of that text file (ok its a little bit more complicated in real life, but its a good way to think about it).
Once you've made a change to the database (e.g. added a row) the database file is saved onto the disk thus persisting it. If the phone is turned off or the app is quit then the database file persists and you can keep connecting to it in the future.

The database is deleted only when your app is deleted, the user clears the data associated with it or you do it programmatically.
Therefore, your app can be killed or the phone rebooted and your database persists. That's why database is considered to be a persistent storage.

what happens if the app is closed or the phone is off?
Answer is No, database not deleted, your data is only deleted when you Uninstall the Application or Clear data from Application->Manage Application->Application_Name from your device.

When a database is created it lives in your applications private file store and is only deleted when you explicitly delete it (using Context.deleteDatabase) or when your application is uninstalled.