When onCreate() and onUpgrade() method run in SQLiteOpenHelper

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Anonymous User · Accepted Answer

SQLiteOpenHelperand onCreate()andand onUpgrade()and and callbacks are invoked when the database is actually opened, for example byand a call toand getWritableDatabase(). The database is not opened when the database helper object itself is created.SQLiteOpenHelper versions the database files. The version number is the int argument passed to theand constructor. In theand database file, the version number is stored inand PRAGMA user_versiononCreate() is only run when the database file did not exist and was just created. If onCreate() returns successfully (doesn't throw an exception), the database is assumed to be created with the requested version number. As an implication, you should not catch SQLExceptions in onCreate() yourself.onUpgrade() is only called when the database file exists but the stored version number is lower than requested in constructor. The onUpgrade() should update the table schema to the requested version.When changing the table schema in code (onCreate()), you should make sure the database is updated. Two main approaches:Delete the old database file so that onCreate() is run again. This is often preferred at development time where you have control over the installed versions and data loss is not an issue. Some ways to to delete the database file:Uninstall the application. Use the application manager or adb uninstall your.package.name from shell.Clear application data. Use the application manager.Increment the database version so that onUpgrade() is invoked. This is slightly more complicated as more code is needed.For development time schema upgrades where data loss is not an issue, you can just use execSQL("DROP TABLE IF EXISTS andlt;tablenameandgt;") in to remove your existing tables and call onCreate() to recreate the database.For released versions, you should implement data migration in onUpgrade() so your users don't lose their data.

Aryan Kumar · Answer

In the SQLiteOpenHelper class, the onCreate() and
onUpgrade() methods are used to manage the creation and upgrading of an SQLite database. These methods are called in specific scenarios as follows:
onCreate():
The onCreate() method is called when the database is being created for the first time.It is executed automatically by the SQLiteOpenHelper class when you instantiate it with a database name that does not exist.In the onCreate() method, you define the initial schema and structure of your database by executing SQL statements to create tables and define their columns.You should also perform any necessary initial data population in this method if required.
onUpgrade():
The onUpgrade() method is called when a new version of the database is detected.It is executed automatically by the SQLiteOpenHelper class when you instantiate it with an increased database version number compared to the existing database on the device.In the onUpgrade() method, you handle the necessary database schema changes and data migrations to accommodate the new version.Typically, you use conditional statements (IF or CASE) to check the current database version and apply the appropriate database alterations using SQL statements such as
ALTER TABLE or DROP TABLE.You can also perform data transformations or migrations if required.It's important to handle version upgrades carefully to avoid data loss or inconsistencies, and to ensure backward compatibility with existing installations.
The SQLiteOpenHelper class manages the database lifecycle and determines when to call the
onCreate() and onUpgrade() methods based on the database version provided. It internally keeps track of the database version and compares it with the version specified during instantiation.
When you instantiate an instance of the SQLiteOpenHelper class, you provide a database name, an initial database version, and optionally, an implementation of the
onCreate() and onUpgrade() methods. The framework takes care of invoking these methods as needed when you interact with the database using the helper class.
It's worth noting that the onCreate() method is only called once, during the initial creation of the database, while the
onUpgrade() method is called whenever the database version is incremented.

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When onCreate() and onUpgrade() method run in SQLiteOpenHelper

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