package com.newsrob.util;
/*
* 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.
*/
import java.io.File;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
/**
* 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.
* <p>
* For an example, see the NotePadProvider class in the NotePad sample
* application, in the <em>samples/</em> directory of the SDK.
* </p>
*/
public abstract class SQLiteOpenHelper {
private static final String TAG = SQLiteOpenHelper.class.getSimpleName();
private final Context mContext;
private final String mName;
private final String mPath;
private final CursorFactory mFactory;
private final int mNewVersion;
private SQLiteDatabase mDatabase = null;
private SQLiteDatabase mReadOnlyDatabase = null;
private boolean mIsInitializing = false;
/**
* 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.
*
* @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
*/
public SQLiteOpenHelper(Context context, String path, String name, CursorFactory factory, int version) {
if (version < 1)
throw new IllegalArgumentException("Version must be >= 1, was " + version);
mContext = context;
mName = name;
mFactory = factory;
mNewVersion = version;
mPath = path;
}
/**
* Create and/or open a database that will be used for reading and writing.
* 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 it.
*
* <p>
* Errors such as bad permissions or a full disk may cause this operation to
* fail, but future attempts may succeed if the problem is fixed.
* </p>
*
* @throws SQLiteException
* if the database cannot be opened for writing
* @return a read/write database object valid until {@link #close} is called
*/
public synchronized SQLiteDatabase getWritableDatabase() {
if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
return mDatabase; // The database is already open for business
}
if (mIsInitializing) {
throw new IllegalStateException("getWritableDatabase called recursively");
}
// If we have a read-only database open, someone could be using it
// (though they shouldn't), which would cause a lock to be held on
// the file, and our attempts to open the database read-write would
// fail waiting for the file lock. To prevent that, we acquire the
// lock on the read-only database, which shuts out other users.
boolean success = false;
SQLiteDatabase db = null;
try {
mIsInitializing = true;
if (mName == null) {
db = SQLiteDatabase.create(null);
} else {
if (mPath != null)
db = SQLiteDatabase.openOrCreateDatabase(new File(mPath, mName), mFactory);
else
db = mContext.openOrCreateDatabase(mName, 0, mFactory);
}
int version = db.getVersion();
if (version != mNewVersion) {
db.beginTransaction();
try {
if (version == 0) {
onCreate(db);
} else {
onUpgrade(db, version, mNewVersion);
}
db.setVersion(mNewVersion);
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}
}
onOpen(db);
success = true;
return db;
} finally {
mIsInitializing = false;
if (success) {
if (mDatabase != null) {
try {
mDatabase.close();
} catch (Exception e) {
}
}
mDatabase = db;
} else {
if (db != null)
db.close();
}
}
}
/**
* Create and/or open a database that will be used for reading and writing.
* 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 it.
*
* <p>
* Errors such as bad permissions or a full disk may cause this operation to
* fail, but future attempts may succeed if the problem is fixed.
* </p>
*
* @throws SQLiteException
* if the database cannot be opened for writing
* @return a read/write database object valid until {@link #close} is called
*/
public synchronized SQLiteDatabase getReadOnlyDatabase() {
// Do the actual initialization first
if (mDatabase == null)
getWritableDatabase();
if (mReadOnlyDatabase != null && mReadOnlyDatabase.isOpen() && !mReadOnlyDatabase.isReadOnly()) {
return mReadOnlyDatabase; // The database is already open for
// business
}
/*
* if (mIsInitializing) { throw new
* IllegalStateException("getReadOnlyDatabase called recursively"); }
*/
// If we have a read-only database open, someone could be using it
// (though they shouldn't), which would cause a lock to be held on
// the file, and our attempts to open the database read-write would
// fail waiting for the file lock. To prevent that, we acquire the
// lock on the read-only database, which shuts out other users.
boolean success = false;
SQLiteDatabase db = null;
try {
// mIsInitializing = true;
if (mName == null) {
db = SQLiteDatabase.create(null);
} else {
if (mPath != null)
db = SQLiteDatabase.openOrCreateDatabase(new File(mPath, mName), mFactory);
else
db = mContext.openOrCreateDatabase(mName, 0, mFactory);
}
// skip as it's done above already
if (false) {
int version = db.getVersion();
if (version != mNewVersion) {
db.beginTransaction();
try {
if (version == 0) {
onCreate(db);
} else {
onUpgrade(db, version, mNewVersion);
}
db.setVersion(mNewVersion);
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}
}
}
onOpen(db);
success = true;
return db;
} finally {
// mIsInitializing = false;
if (success) {
if (mReadOnlyDatabase != null) {
try {
mReadOnlyDatabase.close();
} catch (Exception e) {
}
}
mReadOnlyDatabase = db;
} else {
if (db != null)
db.close();
}
}
}
/**
* 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.
*
* <p>
* The SQLite ALTER TABLE documentation can be found <a
* href="http://sqlite.org/lang_altertable.html">here</a>. 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.
*
* @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 has been opened. Override method should check
* {@link SQLiteDatabase#isReadOnly} before updating the database.
*
* @param db
* The database.
*/
public void onOpen(SQLiteDatabase db) {
}
}