Migrate data from one version to another - Android Sqlite

Question

In the application I am working on, I have to save the data from a specific table when the application is updated. This action needs to happen before the table is discarded in the onUpgrade method. I need to do this because when the application is updated I want the user to continue logging into the system after the update. User data is the only data I want to reuse. my onUpgrade method is like this:

public void onUpgrade(SQLiteDatabase db, ConnectionSource connectionSource, int oldVersion, int newVersion) {
try {

    TableUtils.dropTable(connectionSource, User.class, true);
    ... other tables


    // after we drop the old databases, we create the new ones
    onCreate(db, connectionSource);

} catch (SQLException e) {
    Log.e(DatabaseHelper.class.getName(), "Can't drop databases", e);
    throw new RuntimeException(e);
}
}

How can I implement this persistence?

Answer 1

I don’t know what kind of upgrade you want to do to the database but this upgrade can be done with or without the need to delete and then recreate all tables.
For this, in the method onUpdate(), use SQL commands of type ALTER TABLE and CREATE TABLE to make the changes.

If this is not feasible/practical or just want to keep some data, read this data to memory, do the drop of the tables, call the method onCreate() and restore saved data.

Answer 2

One option would be to not save the user data in the database but in sharedPreferences, that do not work with upgrade.