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A library jar that provides APIs for Applications written for the Google Android Platform.

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/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.database.sqlite;

import android.content.Context;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.util.Log;

/**
 * A helper class to manage database creation and version management.
 *
 * 

You create a subclass implementing {@link #onCreate}, {@link #onUpgrade} and * optionally {@link #onOpen}, 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 {@link android.content.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 abstract class SQLiteOpenHelper { private static final String TAG = SQLiteOpenHelper.class.getSimpleName(); // When true, getReadableDatabase returns a read-only database if it is just being opened. // The database handle is reopened in read/write mode when getWritableDatabase is called. // We leave this behavior disabled in production because it is inefficient and breaks // many applications. For debugging purposes it can be useful to turn on strict // read-only semantics to catch applications that call getReadableDatabase when they really // wanted getWritableDatabase. private static final boolean DEBUG_STRICT_READONLY = false; private final Context mContext; private final String mName; private final CursorFactory mFactory; private final int mNewVersion; private SQLiteDatabase mDatabase; private boolean mIsInitializing; private boolean mEnableWriteAheadLogging; private final DatabaseErrorHandler mErrorHandler; /** * 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 {@link #getWritableDatabase} or * {@link #getReadableDatabase} is called. * * @param context to use to open or create the database * @param name of the database file, or null for an in-memory database * @param factory to use for creating cursor objects, or null for the default * @param version number of the database (starting at 1); if the database is older, * {@link #onUpgrade} will be used to upgrade the database; if the database is * newer, {@link #onDowngrade} will be used to downgrade the database */ public SQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) { this(context, name, factory, version, null); } /** * Create a helper object to create, open, and/or manage a database. * The database is not actually created or opened until one of * {@link #getWritableDatabase} or {@link #getReadableDatabase} is called. * *

Accepts input param: a concrete instance of {@link DatabaseErrorHandler} to be * used to handle corruption when sqlite reports database corruption.

* * @param context to use to open or create the database * @param name of the database file, or null for an in-memory database * @param factory to use for creating cursor objects, or null for the default * @param version number of the database (starting at 1); if the database is older, * {@link #onUpgrade} will be used to upgrade the database; if the database is * newer, {@link #onDowngrade} will be used to downgrade the database * @param errorHandler the {@link DatabaseErrorHandler} to be used when sqlite reports database * corruption, or null to use the default error handler. */ public SQLiteOpenHelper(Context context, String name, CursorFactory factory, int version, DatabaseErrorHandler errorHandler) { if (version < 1) throw new IllegalArgumentException("Version must be >= 1, was " + version); mContext = context; mName = name; mFactory = factory; mNewVersion = version; mErrorHandler = errorHandler; } /** * Return the name of the SQLite database being opened, as given to * the constructor. */ public String getDatabaseName() { return mName; } /** * 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. * * @param enabled True if write-ahead logging should be enabled, false if it * should be disabled. * * @see SQLiteDatabase#enableWriteAheadLogging() */ public void setWriteAheadLoggingEnabled(boolean enabled) { synchronized (this) { if (mEnableWriteAheadLogging != enabled) { if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) { if (enabled) { mDatabase.enableWriteAheadLogging(); } else { mDatabase.disableWriteAheadLogging(); } } mEnableWriteAheadLogging = enabled; } } } /** * 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 * {@link #onCreate}, {@link #onUpgrade} and/or {@link #onOpen} 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 {@link #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 {@link android.content.ContentProvider#onCreate ContentProvider.onCreate()}. * * @throws SQLiteException if the database cannot be opened for writing * @return a read/write database object valid until {@link #close} is called */ public SQLiteDatabase getWritableDatabase() { synchronized (this) { return getDatabaseLocked(true); } } /** * Create and/or open a database. This will be the same object returned by * {@link #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 {@link #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 {@link #getWritableDatabase}, this method may * take a long time to return, so you should not call it from the * application main thread, including from * {@link android.content.ContentProvider#onCreate ContentProvider.onCreate()}. * * @throws SQLiteException if the database cannot be opened * @return a database object valid until {@link #getWritableDatabase} * or {@link #close} is called. */ public SQLiteDatabase getReadableDatabase() { synchronized (this) { return getDatabaseLocked(false); } } private SQLiteDatabase getDatabaseLocked(boolean writable) { if (mDatabase != null) { if (!mDatabase.isOpen()) { // Darn! The user closed the database by calling mDatabase.close(). mDatabase = null; } else if (!writable || !mDatabase.isReadOnly()) { // The database is already open for business. return mDatabase; } } if (mIsInitializing) { throw new IllegalStateException("getDatabase called recursively"); } SQLiteDatabase db = mDatabase; try { mIsInitializing = true; if (db != null) { if (writable && db.isReadOnly()) { db.reopenReadWrite(); } } else if (mName == null) { db = SQLiteDatabase.create(null); } else { try { if (DEBUG_STRICT_READONLY && !writable) { final String path = mContext.getDatabasePath(mName).getPath(); db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY, mErrorHandler); } else { db = mContext.openOrCreateDatabase(mName, mEnableWriteAheadLogging ? Context.MODE_ENABLE_WRITE_AHEAD_LOGGING : 0, mFactory, mErrorHandler); } } catch (SQLiteException ex) { if (writable) { throw ex; } Log.e(TAG, "Couldn't open " + mName + " for writing (will try read-only):", ex); final String path = mContext.getDatabasePath(mName).getPath(); db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY, mErrorHandler); } } onConfigure(db); final int version = db.getVersion(); if (version != mNewVersion) { if (db.isReadOnly()) { throw new SQLiteException("Can't upgrade read-only database from version " + db.getVersion() + " to " + mNewVersion + ": " + mName); } db.beginTransaction(); try { if (version == 0) { onCreate(db); } else { if (version > mNewVersion) { onDowngrade(db, version, mNewVersion); } else { onUpgrade(db, version, mNewVersion); } } db.setVersion(mNewVersion); db.setTransactionSuccessful(); } finally { db.endTransaction(); } } onOpen(db); if (db.isReadOnly()) { Log.w(TAG, "Opened " + mName + " in read-only mode"); } mDatabase = db; return db; } finally { mIsInitializing = false; if (db != null && db != mDatabase) { db.close(); } } } /** * Close any open database object. */ public synchronized void close() { if (mIsInitializing) throw new IllegalStateException("Closed during initialization"); if (mDatabase != null && mDatabase.isOpen()) { mDatabase.close(); mDatabase = null; } } /** * 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 {@link #onCreate}, {@link #onUpgrade}, * {@link #onDowngrade}, or {@link #onOpen} 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 {@link SQLiteDatabase#enableWriteAheadLogging} * {@link SQLiteDatabase#setForeignKeyConstraintsEnabled}, * {@link SQLiteDatabase#setLocale}, {@link SQLiteDatabase#setMaximumSize}, * or executing PRAGMA statements. *

* * @param db The database. */ public void onConfigure(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. * * @param db The database. */ public abstract void onCreate(SQLiteDatabase db); /** * 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. *

* * @param db The database. * @param oldVersion The old database version. * @param newVersion The new database version. */ public abstract void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion); /** * Called when the database needs to be downgraded. This is strictly similar to * {@link #onUpgrade} 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. *

* * @param db The database. * @param oldVersion The old database version. * @param newVersion The new database version. */ public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) { throw new SQLiteException("Can't downgrade database from version " + oldVersion + " to " + newVersion); } /** * Called when the database has been opened. The implementation * should check {@link SQLiteDatabase#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 {@link #onConfigure} instead. *

* * @param db The database. */ public void onOpen(SQLiteDatabase db) {} }




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