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.
Public Constructors | |||||||||||
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Create a helper object to create, open, and/or manage a database.
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Create a helper object to create, open, and/or manage a database.
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Public Methods | |||||||||||
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Close any open database object.
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Return the name of the SQLite database being opened, as given to
the constructor.
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Create and/or open a database.
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Create and/or open a database that will be used for reading and writing.
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Called when the database connection is being configured, to enable features
such as write-ahead logging or foreign key support.
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Called when the database is created for the first time.
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Called when the database needs to be downgraded.
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Called when the database has been opened.
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Called when the database needs to be upgraded.
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Enables or disables the use of write-ahead logging for the database.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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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.
context | to use to open or create the database |
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name | of the database file, or null for an in-memory database |
factory | to use for creating cursor objects, or null for the default |
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
|
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.
context | to use to open or create the database |
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name | of the database file, or null for an in-memory database |
factory | to use for creating cursor objects, or null for the default |
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 |
errorHandler | the DatabaseErrorHandler to be used when sqlite reports database
corruption, or null to use the default error handler.
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Return the name of the SQLite database being opened, as given to the constructor.
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()
.
getWritableDatabase()
or close()
is called.
SQLiteException | if the database cannot be opened |
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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()
.
close()
is called
SQLiteException | if the database cannot be opened for writing |
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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.
db | The database. |
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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.
db | The database. |
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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.
db | The database. |
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oldVersion | The old database version. |
newVersion | The new database version. |
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.
db | The database. |
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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.
db | The database. |
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oldVersion | The old database version. |
newVersion | The new database version. |
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.
enabled | True if write-ahead logging should be enabled, false if it should be disabled. |
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