public abstract class SQLiteOpenHelper { private static final String TAG = SQLiteOpenHelper.class .getSimpleName(); private final Context mContext; private final String mName; private final CursorFactory mFactory; private final int mNewVersion; private SQLiteDatabase mDatabase = 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 * [email protected] #getWritableDatabase} or [email protected] #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, [email protected] #onUpgrade} will be used to upgrade the database */ public SDCardSQLiteOpenHelper(Context context, 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; } /** * 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 * [email protected] #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 [email protected] #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 { String path = getDatabasePath(mName).getPath(); db = SQLiteDatabase.openOrCreateDatabase(path, 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; } catch (Exception e) { e.printStackTrace(); } finally { mIsInitializing = false; if (success) { if (mDatabase != null) { try { mDatabase.close(); } catch (Exception e) { } } mDatabase = db; } else { if (db != null) db.close(); } } return db; } /** * Create and/or open a database. This will be the same object returned by * [email protected] #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 [email protected] #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. * * @throws SQLiteException * if the database cannot be opened * @return a database object valid until [email protected] #getWritableDatabase} or * [email protected] #close} is called. */ public synchronized SQLiteDatabase getReadableDatabase() { if (mDatabase != null && mDatabase.isOpen()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException( "getReadableDatabase called recursively"); } try { return getWritableDatabase(); } catch (SQLiteException e) { if (mName == null) throw e; // Can't open a temp database read-only! Log.e(TAG, "Couldn't open " + mName + " for writing (will try read-only):", e); } SQLiteDatabase db = null; try { mIsInitializing = true; String path = getDatabasePath(mName).getPath(); db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READWRITE); if (db.getVersion() != mNewVersion) { throw new SQLiteException( "Can't upgrade read-only database from version " + db.getVersion() + " to " + mNewVersion + ": " + path); } onOpen(db); Log.w(TAG, "Opened " + mName + " in read-only mode"); mDatabase = db; return mDatabase; } 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; } } public File getDatabasePath(String name) { String EXTERN_PATH = null; if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED) == true) { String dbPath = mContext.getString(R.string.dir) + mContext.getString(R.string.db_dir) + "/"; EXTERN_PATH = android.os.Environment.getExternalStorageDirectory() .getAbsolutePath() + dbPath; File f = new File(EXTERN_PATH); if (!f.exists()) { f.mkdirs(); } } return new File(EXTERN_PATH + name); } /** * 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 * [email protected] SQLiteDatabase#isReadOnly} before updating the database. * * @param db * The database. */ public void onOpen(SQLiteDatabase db) { }}其实也就是改了一下生成文件的 路径。