android/database/sqlite/SQLiteOpenHelper.java - platform/prebuilts/fullsdk/sources/android-28 - Git at Google

 /*
  * 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.annotation.IntRange;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.Context;
 import android.database.DatabaseErrorHandler;
 import android.database.SQLException;
 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 import android.os.FileUtils;
 import android.util.Log;

 import com.android.internal.util.Preconditions;

 import java.io.File;

 /**
  * A helper class to manage database creation and version management.
  *
  * <p>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>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.
  *
  * <p>For an example, see the NotePadProvider class in the NotePad sample application,
  * in the <em>samples/</em> directory of the SDK.</p>
  *
  * <p class="note"><strong>Note:</strong> this class assumes
  * monotonically increasing version numbers for upgrades.</p>
  */
 public abstract class SQLiteOpenHelper {
     private static final String TAG = SQLiteOpenHelper.class.getSimpleName();

     private final Context mContext;
     private final String mName;
     private final int mNewVersion;
     private final int mMinimumSupportedVersion;

     private SQLiteDatabase mDatabase;
     private boolean mIsInitializing;
     private SQLiteDatabase.OpenParams.Builder mOpenParamsBuilder;

     /**
      * 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 for locating paths to the 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(@Nullable Context context, @Nullable String name,
             @Nullable 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.
      *
      * <p>Accepts input param: a concrete instance of {@link DatabaseErrorHandler} to be
      * used to handle corruption when sqlite reports database corruption.</p>
      *
      * @param context to use for locating paths to the 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(@Nullable Context context, @Nullable String name,
             @Nullable CursorFactory factory, int version,
             @Nullable DatabaseErrorHandler errorHandler) {
         this(context, name, factory, version, 0, errorHandler);
     }

     /**
      * 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 for locating paths to the the database
      * @param name of the database file, or null for an in-memory database
      * @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 openParams configuration parameters that are used for opening {@link SQLiteDatabase}.
      *        Please note that {@link SQLiteDatabase#CREATE_IF_NECESSARY} flag will always be
      *        set when the helper opens the database
      */
     public SQLiteOpenHelper(@Nullable Context context, @Nullable String name, int version,
             @NonNull SQLiteDatabase.OpenParams openParams) {
         this(context, name, version, 0, openParams.toBuilder());
     }

     /**
      * Same as {@link #SQLiteOpenHelper(Context, String, CursorFactory, int, DatabaseErrorHandler)}
      * but also accepts an integer minimumSupportedVersion as a convenience for upgrading very old
      * versions of this database that are no longer supported. If a database with older version that
      * minimumSupportedVersion is found, it is simply deleted and a new database is created with the
      * given name and version
      *
      * @param context to use for locating paths to the the database
      * @param name the name of the database file, null for a temporary in-memory database
      * @param factory to use for creating cursor objects, null for default
      * @param version the required version of the database
      * @param minimumSupportedVersion the minimum version that is supported to be upgraded to
      *            {@code version} via {@link #onUpgrade}. If the current database version is lower
      *            than this, database is simply deleted and recreated with the version passed in
      *            {@code version}. {@link #onBeforeDelete} is called before deleting the database
      *            when this happens. This is 0 by default.
      * @param errorHandler the {@link DatabaseErrorHandler} to be used when sqlite reports database
      *            corruption, or null to use the default error handler.
      * @see #onBeforeDelete(SQLiteDatabase)
      * @see #SQLiteOpenHelper(Context, String, CursorFactory, int, DatabaseErrorHandler)
      * @see #onUpgrade(SQLiteDatabase, int, int)
      * @hide
      */
     public SQLiteOpenHelper(@Nullable Context context, @Nullable String name,
             @Nullable CursorFactory factory, int version,
             int minimumSupportedVersion, @Nullable DatabaseErrorHandler errorHandler) {
         this(context, name, version, minimumSupportedVersion,
                 new SQLiteDatabase.OpenParams.Builder());
         mOpenParamsBuilder.setCursorFactory(factory);
         mOpenParamsBuilder.setErrorHandler(errorHandler);
     }

     private SQLiteOpenHelper(@Nullable Context context, @Nullable String name, int version,
             int minimumSupportedVersion,
             @NonNull SQLiteDatabase.OpenParams.Builder openParamsBuilder) {
         Preconditions.checkNotNull(openParamsBuilder);
         if (version < 1) throw new IllegalArgumentException("Version must be >= 1, was " + version);

         mContext = context;
         mName = name;
         mNewVersion = version;
         mMinimumSupportedVersion = Math.max(0, minimumSupportedVersion);
         setOpenParamsBuilder(openParamsBuilder);
     }

     /**
      * 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 (mOpenParamsBuilder.isWriteAheadLoggingEnabled() != enabled) {
                 if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
                     if (enabled) {
                         mDatabase.enableWriteAheadLogging();
                     } else {
                         mDatabase.disableWriteAheadLogging();
                     }
                 }
                 mOpenParamsBuilder.setWriteAheadLoggingEnabled(enabled);
             }
             // Compatibility WAL is disabled if an app disables or enables WAL
             mOpenParamsBuilder.addOpenFlags(SQLiteDatabase.DISABLE_COMPATIBILITY_WAL);
         }
     }

     /**
      * Configures <a href="https://sqlite.org/malloc.html#lookaside">lookaside memory allocator</a>
      *
      * <p>This method should be called from the constructor of the subclass,
      * before opening the database, since lookaside memory configuration can only be changed
      * when no connection is using it
      *
      * <p>SQLite default settings will be used, if this method isn't called.
      * Use {@code setLookasideConfig(0,0)} to disable lookaside
      *
      * <p><strong>Note:</strong> Provided slotSize/slotCount configuration is just a recommendation.
      * The system may choose different values depending on a device, e.g. lookaside allocations
      * can be disabled on low-RAM devices
      *
      * @param slotSize The size in bytes of each lookaside slot.
      * @param slotCount The total number of lookaside memory slots per database connection.
      */
     public void setLookasideConfig(@IntRange(from = 0) final int slotSize,
             @IntRange(from = 0) final int slotCount) {
         synchronized (this) {
             if (mDatabase != null && mDatabase.isOpen()) {
                 throw new IllegalStateException(
                         "Lookaside memory config cannot be changed after opening the database");
             }
             mOpenParamsBuilder.setLookasideConfig(slotSize, slotCount);
         }
     }

     /**
      * Sets configuration parameters that are used for opening {@link SQLiteDatabase}.
      * <p>Please note that {@link SQLiteDatabase#CREATE_IF_NECESSARY} flag will always be set when
      * opening the database
      *
      * @param openParams configuration parameters that are used for opening {@link SQLiteDatabase}.
      * @throws IllegalStateException if the database is already open
      */
     public void setOpenParams(@NonNull SQLiteDatabase.OpenParams openParams) {
         Preconditions.checkNotNull(openParams);
         synchronized (this) {
             if (mDatabase != null && mDatabase.isOpen()) {
                 throw new IllegalStateException(
                         "OpenParams cannot be set after opening the database");
             }
             setOpenParamsBuilder(new SQLiteDatabase.OpenParams.Builder(openParams));
         }
     }

     private void setOpenParamsBuilder(SQLiteDatabase.OpenParams.Builder openParamsBuilder) {
         mOpenParamsBuilder = openParamsBuilder;
         mOpenParamsBuilder.addOpenFlags(SQLiteDatabase.CREATE_IF_NECESSARY);
     }

     /**
      * Sets the maximum number of milliseconds that SQLite connection is allowed to be idle
      * before it is closed and removed from the pool.
      *
      * <p>This method should be called from the constructor of the subclass,
      * before opening the database
      *
      * @param idleConnectionTimeoutMs timeout in milliseconds. Use {@link Long#MAX_VALUE} value
      * to allow unlimited idle connections.
      */
     public void setIdleConnectionTimeout(@IntRange(from = 0) final long idleConnectionTimeoutMs) {
         synchronized (this) {
             if (mDatabase != null && mDatabase.isOpen()) {
                 throw new IllegalStateException(
                         "Connection timeout setting cannot be changed after opening the database");
             }
             mOpenParamsBuilder.setIdleConnectionTimeout(idleConnectionTimeoutMs);
         }
     }

     /**
      * 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.
      *
      * <p>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.</p>
      *
      * <p class="caution">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.
      *
      * <p class="caution">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.createInMemory(mOpenParamsBuilder.build());
             } else {
                 final File filePath = mContext.getDatabasePath(mName);
                 SQLiteDatabase.OpenParams params = mOpenParamsBuilder.build();
                 try {
                     db = SQLiteDatabase.openDatabase(filePath, params);
                     // Keep pre-O-MR1 behavior by resetting file permissions to 660
                     setFilePermissionsForDb(filePath.getPath());
                 } catch (SQLException ex) {
                     if (writable) {
                         throw ex;
                     }
                     Log.e(TAG, "Couldn't open " + mName
                             + " for writing (will try read-only):", ex);
                     params = params.toBuilder().addOpenFlags(SQLiteDatabase.OPEN_READONLY).build();
                     db = SQLiteDatabase.openDatabase(filePath, params);
                 }
             }

             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);
                 }

                 if (version > 0 && version < mMinimumSupportedVersion) {
                     File databaseFile = new File(db.getPath());
                     onBeforeDelete(db);
                     db.close();
                     if (SQLiteDatabase.deleteDatabase(databaseFile)) {
                         mIsInitializing = false;
                         return getDatabaseLocked(writable);
                     } else {
                         throw new IllegalStateException("Unable to delete obsolete database "
                                 + mName + " with version " + version);
                     }
                 } else {
                     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();
             }
         }
     }

     private static void setFilePermissionsForDb(String dbPath) {
         int perms = FileUtils.S_IRUSR | FileUtils.S_IWUSR | FileUtils.S_IRGRP | FileUtils.S_IWGRP;
         FileUtils.setPermissions(dbPath, perms, -1, -1);
     }

     /**
      * 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.
      * <p>
      * 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.
      * </p>
      * <p>
      * 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.
      * </p>
      *
      * @param db The database.
      */
     public void onConfigure(SQLiteDatabase db) {}

     /**
      * Called before the database is deleted when the version returned by
      * {@link SQLiteDatabase#getVersion()} is lower than the minimum supported version passed (if at
      * all) while creating this helper. After the database is deleted, a fresh database with the
      * given version is created. This will be followed by {@link #onConfigure(SQLiteDatabase)} and
      * {@link #onCreate(SQLiteDatabase)} being called with a new SQLiteDatabase object
      *
      * @param db the database opened with this helper
      * @see #SQLiteOpenHelper(Context, String, CursorFactory, int, int, DatabaseErrorHandler)
      * @hide
      */
     public void onBeforeDelete(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.
      *
      * <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.
      * </p><p>
      * This method executes within a transaction.  If an exception is thrown, all changes
      * will automatically be rolled back.
      * </p>
      *
      * @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
      *
      * <p>
      * This method executes within a transaction.  If an exception is thrown, all changes
      * will automatically be rolled back.
      * </p>
      *
      * @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.
      * <p>
      * 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.
      * </p>
      *
      * @param db The database.
      */
     public void onOpen(SQLiteDatabase db) {}
 }
	/*
	* 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.annotation.IntRange;
	import android.annotation.NonNull;
	import android.annotation.Nullable;
	import android.content.Context;
	import android.database.DatabaseErrorHandler;
	import android.database.SQLException;
	import android.database.sqlite.SQLiteDatabase.CursorFactory;
	import android.os.FileUtils;
	import android.util.Log;

	import com.android.internal.util.Preconditions;

	import java.io.File;

	/**
	* A helper class to manage database creation and version management.
	*
	* <p>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>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.
	*
	* <p>For an example, see the NotePadProvider class in the NotePad sample application,
	* in the <em>samples/</em> directory of the SDK.</p>
	*
	* <p class="note"><strong>Note:</strong> this class assumes
	* monotonically increasing version numbers for upgrades.</p>
	*/
	public abstract class SQLiteOpenHelper {
	private static final String TAG = SQLiteOpenHelper.class.getSimpleName();

	private final Context mContext;
	private final String mName;
	private final int mNewVersion;
	private final int mMinimumSupportedVersion;

	private SQLiteDatabase mDatabase;
	private boolean mIsInitializing;
	private SQLiteDatabase.OpenParams.Builder mOpenParamsBuilder;

	/**
	* 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 for locating paths to the 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(@Nullable Context context, @Nullable String name,
	@Nullable 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.
	*
	* <p>Accepts input param: a concrete instance of {@link DatabaseErrorHandler} to be
	* used to handle corruption when sqlite reports database corruption.</p>
	*
	* @param context to use for locating paths to the 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(@Nullable Context context, @Nullable String name,
	@Nullable CursorFactory factory, int version,
	@Nullable DatabaseErrorHandler errorHandler) {
	this(context, name, factory, version, 0, errorHandler);
	}

	/**
	* 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 for locating paths to the the database
	* @param name of the database file, or null for an in-memory database
	* @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 openParams configuration parameters that are used for opening {@link SQLiteDatabase}.
	* Please note that {@link SQLiteDatabase#CREATE_IF_NECESSARY} flag will always be
	* set when the helper opens the database
	*/
	public SQLiteOpenHelper(@Nullable Context context, @Nullable String name, int version,
	@NonNull SQLiteDatabase.OpenParams openParams) {
	this(context, name, version, 0, openParams.toBuilder());
	}

	/**
	* Same as {@link #SQLiteOpenHelper(Context, String, CursorFactory, int, DatabaseErrorHandler)}
	* but also accepts an integer minimumSupportedVersion as a convenience for upgrading very old
	* versions of this database that are no longer supported. If a database with older version that
	* minimumSupportedVersion is found, it is simply deleted and a new database is created with the
	* given name and version
	*
	* @param context to use for locating paths to the the database
	* @param name the name of the database file, null for a temporary in-memory database
	* @param factory to use for creating cursor objects, null for default
	* @param version the required version of the database
	* @param minimumSupportedVersion the minimum version that is supported to be upgraded to
	* {@code version} via {@link #onUpgrade}. If the current database version is lower
	* than this, database is simply deleted and recreated with the version passed in
	* {@code version}. {@link #onBeforeDelete} is called before deleting the database
	* when this happens. This is 0 by default.
	* @param errorHandler the {@link DatabaseErrorHandler} to be used when sqlite reports database
	* corruption, or null to use the default error handler.
	* @see #onBeforeDelete(SQLiteDatabase)
	* @see #SQLiteOpenHelper(Context, String, CursorFactory, int, DatabaseErrorHandler)
	* @see #onUpgrade(SQLiteDatabase, int, int)
	* @hide
	*/
	public SQLiteOpenHelper(@Nullable Context context, @Nullable String name,
	@Nullable CursorFactory factory, int version,
	int minimumSupportedVersion, @Nullable DatabaseErrorHandler errorHandler) {
	this(context, name, version, minimumSupportedVersion,
	new SQLiteDatabase.OpenParams.Builder());
	mOpenParamsBuilder.setCursorFactory(factory);
	mOpenParamsBuilder.setErrorHandler(errorHandler);
	}

	private SQLiteOpenHelper(@Nullable Context context, @Nullable String name, int version,
	int minimumSupportedVersion,
	@NonNull SQLiteDatabase.OpenParams.Builder openParamsBuilder) {
	Preconditions.checkNotNull(openParamsBuilder);
	if (version < 1) throw new IllegalArgumentException("Version must be >= 1, was " + version);

	mContext = context;
	mName = name;
	mNewVersion = version;
	mMinimumSupportedVersion = Math.max(0, minimumSupportedVersion);
	setOpenParamsBuilder(openParamsBuilder);
	}

	/**
	* 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 (mOpenParamsBuilder.isWriteAheadLoggingEnabled() != enabled) {
	if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
	if (enabled) {
	mDatabase.enableWriteAheadLogging();
	} else {
	mDatabase.disableWriteAheadLogging();
	}
	}
	mOpenParamsBuilder.setWriteAheadLoggingEnabled(enabled);
	}
	// Compatibility WAL is disabled if an app disables or enables WAL
	mOpenParamsBuilder.addOpenFlags(SQLiteDatabase.DISABLE_COMPATIBILITY_WAL);
	}
	}

	/**
	* Configures <a href="https://sqlite.org/malloc.html#lookaside">lookaside memory allocator</a>
	*
	* <p>This method should be called from the constructor of the subclass,
	* before opening the database, since lookaside memory configuration can only be changed
	* when no connection is using it
	*
	* <p>SQLite default settings will be used, if this method isn't called.
	* Use {@code setLookasideConfig(0,0)} to disable lookaside
	*
	* <p><strong>Note:</strong> Provided slotSize/slotCount configuration is just a recommendation.
	* The system may choose different values depending on a device, e.g. lookaside allocations
	* can be disabled on low-RAM devices
	*
	* @param slotSize The size in bytes of each lookaside slot.
	* @param slotCount The total number of lookaside memory slots per database connection.
	*/
	public void setLookasideConfig(@IntRange(from = 0) final int slotSize,
	@IntRange(from = 0) final int slotCount) {
	synchronized (this) {
	if (mDatabase != null && mDatabase.isOpen()) {
	throw new IllegalStateException(
	"Lookaside memory config cannot be changed after opening the database");
	}
	mOpenParamsBuilder.setLookasideConfig(slotSize, slotCount);
	}
	}

	/**
	* Sets configuration parameters that are used for opening {@link SQLiteDatabase}.
	* <p>Please note that {@link SQLiteDatabase#CREATE_IF_NECESSARY} flag will always be set when
	* opening the database
	*
	* @param openParams configuration parameters that are used for opening {@link SQLiteDatabase}.
	* @throws IllegalStateException if the database is already open
	*/
	public void setOpenParams(@NonNull SQLiteDatabase.OpenParams openParams) {
	Preconditions.checkNotNull(openParams);
	synchronized (this) {
	if (mDatabase != null && mDatabase.isOpen()) {
	throw new IllegalStateException(
	"OpenParams cannot be set after opening the database");
	}
	setOpenParamsBuilder(new SQLiteDatabase.OpenParams.Builder(openParams));
	}
	}

	private void setOpenParamsBuilder(SQLiteDatabase.OpenParams.Builder openParamsBuilder) {
	mOpenParamsBuilder = openParamsBuilder;
	mOpenParamsBuilder.addOpenFlags(SQLiteDatabase.CREATE_IF_NECESSARY);
	}

	/**
	* Sets the maximum number of milliseconds that SQLite connection is allowed to be idle
	* before it is closed and removed from the pool.
	*
	* <p>This method should be called from the constructor of the subclass,
	* before opening the database
	*
	* @param idleConnectionTimeoutMs timeout in milliseconds. Use {@link Long#MAX_VALUE} value
	* to allow unlimited idle connections.
	*/
	public void setIdleConnectionTimeout(@IntRange(from = 0) final long idleConnectionTimeoutMs) {
	synchronized (this) {
	if (mDatabase != null && mDatabase.isOpen()) {
	throw new IllegalStateException(
	"Connection timeout setting cannot be changed after opening the database");
	}
	mOpenParamsBuilder.setIdleConnectionTimeout(idleConnectionTimeoutMs);
	}
	}

	/**
	* 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.
	*
	* <p>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.</p>
	*
	* <p class="caution">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.
	*
	* <p class="caution">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.createInMemory(mOpenParamsBuilder.build());
	} else {
	final File filePath = mContext.getDatabasePath(mName);
	SQLiteDatabase.OpenParams params = mOpenParamsBuilder.build();
	try {
	db = SQLiteDatabase.openDatabase(filePath, params);
	// Keep pre-O-MR1 behavior by resetting file permissions to 660
	setFilePermissionsForDb(filePath.getPath());
	} catch (SQLException ex) {
	if (writable) {
	throw ex;
	}
	Log.e(TAG, "Couldn't open " + mName
	+ " for writing (will try read-only):", ex);
	params = params.toBuilder().addOpenFlags(SQLiteDatabase.OPEN_READONLY).build();
	db = SQLiteDatabase.openDatabase(filePath, params);
	}
	}

	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);
	}

	if (version > 0 && version < mMinimumSupportedVersion) {
	File databaseFile = new File(db.getPath());
	onBeforeDelete(db);
	db.close();
	if (SQLiteDatabase.deleteDatabase(databaseFile)) {
	mIsInitializing = false;
	return getDatabaseLocked(writable);
	} else {
	throw new IllegalStateException("Unable to delete obsolete database "
	+ mName + " with version " + version);
	}
	} else {
	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();
	}
	}
	}

	private static void setFilePermissionsForDb(String dbPath) {
	int perms = FileUtils.S_IRUSR \| FileUtils.S_IWUSR \| FileUtils.S_IRGRP \| FileUtils.S_IWGRP;
	FileUtils.setPermissions(dbPath, perms, -1, -1);
	}

	/**
	* 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.
	* <p>
	* 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.
	* </p>
	* <p>
	* 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.
	* </p>
	*
	* @param db The database.
	*/
	public void onConfigure(SQLiteDatabase db) {}

	/**
	* Called before the database is deleted when the version returned by
	* {@link SQLiteDatabase#getVersion()} is lower than the minimum supported version passed (if at
	* all) while creating this helper. After the database is deleted, a fresh database with the
	* given version is created. This will be followed by {@link #onConfigure(SQLiteDatabase)} and
	* {@link #onCreate(SQLiteDatabase)} being called with a new SQLiteDatabase object
	*
	* @param db the database opened with this helper
	* @see #SQLiteOpenHelper(Context, String, CursorFactory, int, int, DatabaseErrorHandler)
	* @hide
	*/
	public void onBeforeDelete(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.
	*
	* <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.
	* </p><p>
	* This method executes within a transaction. If an exception is thrown, all changes
	* will automatically be rolled back.
	* </p>
	*
	* @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
	*
	* <p>
	* This method executes within a transaction. If an exception is thrown, all changes
	* will automatically be rolled back.
	* </p>
	*
	* @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.
	* <p>
	* 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.
	* </p>
	*
	* @param db The database.
	*/
	public void onOpen(SQLiteDatabase db) {}
	}