What the version mean in the abstract class SQLiteOpenHelper of Android

Question

There is a parameter in the constructor of the virtual class SQLiteOpenHelper called version(like below shows)

public SQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) {
        this(context, name, factory, version, null);
    }

What i want to know is what's the meaning of the version?Can anyone help me on this?

Answer 1

Its the Database version you ship with the Application. So in the future if you want to add a table or delete a column or anything which differs from the previous Database version. This version Number will come handy.

This is an example of how I manuplated DB on upgrades of my application: The method is defined by the framework, onUpgrade()

Class Level Variable:

private static final int DATABASE_VERSION = 4;

Check against the current version:

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            if (oldVersion < 2) {
                db.execSQL(DATABASE_CREATEX);
            }
            if (oldVersion < 3) {
                db.execSQL(DATABASE_CREATEC);
            }
            if (oldVersion < 4) {
                final String ALTER_TBL = "ALTER TABLE " + DATABASE_TABLE1
                        + " ADD COLUMN Vcost text;";
                final String ALTER_TBL1 = "ALTER TABLE " + DATABASE_TABLE1
                        + " ADD COLUMN Vmedicine text;";
                db.execSQL(ALTER_TBL);
                db.execSQL(ALTER_TBL1);

                final String ALTER_TBL2 = "ALTER TABLE " + DATABASE_TABLE2
                        + " ADD COLUMN Dcost text;";
                final String ALTER_TBL3 = "ALTER TABLE " + DATABASE_TABLE2
                        + " ADD COLUMN Dmedicine text;";
                db.execSQL(ALTER_TBL2);
                db.execSQL(ALTER_TBL3);

            }

        }

So it checks based on all versions of the DB and it acts according to the current version which is present on the device.

Answer 2

Its a way for you to version your database, which is why you're also required to override the onUpgrade method to handle database upgrades. So say you launch your app with a SQLite database and then later on you change your tables. You would then increment the database version, and when the app updates the onUpgrade method would be executed.

Answer 3

Version :

number of the database (starting at 1); if the database is older, onUpgrade(SQLiteDatabase, int, int) will be used to upgrade the database; if the database is newer, onDowngrade(SQLiteDatabase, int, int) will be used to downgrade the database

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