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Added in API level 1

SQLiteOpenHelper

public abstract class SQLiteOpenHelper
extends Object

java.lang.Object
   ↳ android.database.sqlite.SQLiteOpenHelper


A helper class to manage database creation and version management.

You create a subclass implementing onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int) and optionally onOpen(SQLiteDatabase), and this class takes care of opening the database if it exists, creating it if it does not, and upgrading it as necessary. Transactions are used to make sure the database is always in a sensible state.

This class makes it easy for ContentProvider implementations to defer opening and upgrading the database until first use, to avoid blocking application startup with long-running database upgrades.

For an example, see the NotePadProvider class in the NotePad sample application, in the samples/ directory of the SDK.

Note: this class assumes monotonically increasing version numbers for upgrades.

Summary

Public constructors

SQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version)

Create a helper object to create, open, and/or manage a database.

SQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler)

Create a helper object to create, open, and/or manage a database.

Public methods

void close()

Close any open database object.

String getDatabaseName()

Return the name of the SQLite database being opened, as given to the constructor.

SQLiteDatabase getReadableDatabase()

Create and/or open a database.

SQLiteDatabase getWritableDatabase()

Create and/or open a database that will be used for reading and writing.

void onConfigure(SQLiteDatabase db)

Called when the database connection is being configured, to enable features such as write-ahead logging or foreign key support.

abstract void onCreate(SQLiteDatabase db)

Called when the database is created for the first time.

void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion)

Called when the database needs to be downgraded.

void onOpen(SQLiteDatabase db)

Called when the database has been opened.

abstract void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)

Called when the database needs to be upgraded.

void setWriteAheadLoggingEnabled(boolean enabled)

Enables or disables the use of write-ahead logging for the database.

Inherited methods

From class java.lang.Object

Public constructors

SQLiteOpenHelper

Added in API level 1
SQLiteOpenHelper (Context context, 
                String name, 
                SQLiteDatabase.CursorFactory factory, 
                int version)

Create a helper object to create, open, and/or manage a database. This method always returns very quickly. The database is not actually created or opened until one of getWritableDatabase() or getReadableDatabase() is called.

Parameters
context Context: to use to open or create the database
name String: of the database file, or null for an in-memory database
factory SQLiteDatabase.CursorFactory: to use for creating cursor objects, or null for the default
version int: 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

SQLiteOpenHelper

Added in API level 11
SQLiteOpenHelper (Context context, 
                String name, 
                SQLiteDatabase.CursorFactory factory, 
                int version, 
                DatabaseErrorHandler errorHandler)

Create a helper object to create, open, and/or manage a database. The database is not actually created or opened until one of getWritableDatabase() or getReadableDatabase() is called.

Accepts input param: a concrete instance of DatabaseErrorHandler to be used to handle corruption when sqlite reports database corruption.

Parameters
context Context: to use to open or create the database
name String: of the database file, or null for an in-memory database
factory SQLiteDatabase.CursorFactory: to use for creating cursor objects, or null for the default
version int: 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
errorHandler DatabaseErrorHandler: the DatabaseErrorHandler to be used when sqlite reports database corruption, or null to use the default error handler.

Public methods

close

Added in API level 1
void close ()

Close any open database object.

getDatabaseName

Added in API level 14
String getDatabaseName ()

Return the name of the SQLite database being opened, as given to the constructor.

Returns
String

getReadableDatabase

Added in API level 1
SQLiteDatabase getReadableDatabase ()

Create and/or open a database. This will be the same object returned by getWritableDatabase() unless some problem, such as a full disk, requires the database to be opened read-only. In that case, a read-only database object will be returned. If the problem is fixed, a future call to getWritableDatabase() may succeed, in which case the read-only database object will be closed and the read/write object will be returned in the future.

Like getWritableDatabase(), this method may take a long time to return, so you should not call it from the application main thread, including from ContentProvider.onCreate().

Returns
SQLiteDatabase a database object valid until getWritableDatabase() or close() is called.
Throws
SQLiteException if the database cannot be opened

getWritableDatabase

Added in API level 1
SQLiteDatabase getWritableDatabase ()

Create and/or open a database that will be used for reading and writing. The first time this is called, the database will be opened and onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int) and/or onOpen(SQLiteDatabase) will be called.

Once opened successfully, the database is cached, so you can call this method every time you need to write to the database. (Make sure to call close() when you no longer need the database.) Errors such as bad permissions or a full disk may cause this method to fail, but future attempts may succeed if the problem is fixed.

Database upgrade may take a long time, you should not call this method from the application main thread, including from ContentProvider.onCreate().

Returns
SQLiteDatabase a read/write database object valid until close() is called
Throws
SQLiteException if the database cannot be opened for writing

onConfigure

Added in API level 16
void onConfigure (SQLiteDatabase db)

Called when the database connection is being configured, to enable features such as write-ahead logging or foreign key support.

This method is called before onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int), onDowngrade(SQLiteDatabase, int, int), or onOpen(SQLiteDatabase) are called. It should not modify the database except to configure the database connection as required.

This method should only call methods that configure the parameters of the database connection, such as enableWriteAheadLogging() setForeignKeyConstraintsEnabled(boolean), setLocale(Locale), setMaximumSize(long), or executing PRAGMA statements.

Parameters
db SQLiteDatabase: The database.

onCreate

Added in API level 1
void onCreate (SQLiteDatabase db)

Called when the database is created for the first time. This is where the creation of tables and the initial population of the tables should happen.

Parameters
db SQLiteDatabase: The database.

onDowngrade

Added in API level 11
void onDowngrade (SQLiteDatabase db, 
                int oldVersion, 
                int newVersion)

Called when the database needs to be downgraded. This is strictly similar to onUpgrade(SQLiteDatabase, int, int) method, but is called whenever current version is newer than requested one. However, this method is not abstract, so it is not mandatory for a customer to implement it. If not overridden, default implementation will reject downgrade and throws SQLiteException

This method executes within a transaction. If an exception is thrown, all changes will automatically be rolled back.

Parameters
db SQLiteDatabase: The database.
oldVersion int: The old database version.
newVersion int: The new database version.

onOpen

Added in API level 1
void onOpen (SQLiteDatabase db)

Called when the database has been opened. The implementation should check isReadOnly() before updating the database.

This method is called after the database connection has been configured and after the database schema has been created, upgraded or downgraded as necessary. If the database connection must be configured in some way before the schema is created, upgraded, or downgraded, do it in onConfigure(SQLiteDatabase) instead.

Parameters
db SQLiteDatabase: The database.

onUpgrade

Added in API level 1
void onUpgrade (SQLiteDatabase db, 
                int oldVersion, 
                int newVersion)

Called when the database needs to be upgraded. The implementation should use this method to drop tables, add tables, or do anything else it needs to upgrade to the new schema version.

The SQLite ALTER TABLE documentation can be found here. If you add new columns you can use ALTER TABLE to insert them into a live table. If you rename or remove columns you can use ALTER TABLE to rename the old table, then create the new table and then populate the new table with the contents of the old table.

This method executes within a transaction. If an exception is thrown, all changes will automatically be rolled back.

Parameters
db SQLiteDatabase: The database.
oldVersion int: The old database version.
newVersion int: The new database version.

setWriteAheadLoggingEnabled

Added in API level 16
void setWriteAheadLoggingEnabled (boolean enabled)

Enables or disables the use of write-ahead logging for the database. Write-ahead logging cannot be used with read-only databases so the value of this flag is ignored if the database is opened read-only.

Parameters
enabled boolean: True if write-ahead logging should be enabled, false if it should be disabled.

See also:

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