Android Open Source - OpenQOTD Quote Database

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 *  Copyright 2011 Thibault Jouannic <thibault@jouannic.fr>. All Rights Reserved.
 *  This file is part of OpenQOTD.//from  w w w .java2 s  .c om
 *
 *  OpenQOTD is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  OpenQOTD is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with OpenQOTD. If not, see <http://www.gnu.org/licenses/>.
 */

package fr.miximum.qotd;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.util.Log;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;

public class QuoteDatabase {
    /**
     * The basic db name, located is the asset directory
     */
    private static final String DB_NAME = "qotd.db";

    /**
     * We need to suffix the db with a dummy extension, to prevent android to compress it
     */
    private static final String DB_FILE_FAKE_EXTEN = ".mp3";

    /**
     * Current db version
     */
    private static final int DB_VERSION = 1;

    /**
     * Name of the table containing quotes
     */
    private static final String QUOTES_TABLE_NAME = "quote";

    /**
     * Helper to manage database creation and upgrade
     */
    private final QuoteDbHelper mDbHelper;

    /**
     * Column map projection
     */
    private static final HashMap<String,String> mColumnMap = buildColumnMap();

    /**
     * Constructor
     * @param context The Context within which to work, used to create the DB
     */
    public QuoteDatabase(Context context) {
      mDbHelper = new QuoteDbHelper(context);
      mDbHelper.initializeDatabase();
    }

    /**
     * Builds a map for all columns that may be requested, which will be given to the
     * SQLiteQueryBuilder. This is a good way to define aliases for column names, but must include
     * all columns, even if the value is the key. This allows the ContentProvider to request
     * columns w/o the need to know real column names and create the alias itself.
     */
    private static HashMap<String,String> buildColumnMap() {
        HashMap<String,String> map = new HashMap<String,String>();
        map.put(Quote._ID, Quote._ID);
        map.put(Quote.QUOTE, Quote.QUOTE);
        return map;
    }

    /**
     * Returns a Cursor positioned at the quote given id
     *
     * @param id id of quote to retrieve
     * @return Cursor positioned to matching word, or null if not found.
     */
    public Cursor getQuote(int id) {
        String selection = Quote._ID + " = ?";
        String[] selectionArgs = new String[] { String.valueOf(id) };

        /* This builds a query that looks like:
         *     SELECT <columns> FROM <table> WHERE rowid = <rowId>
         */
        Cursor c = query(selection, selectionArgs);
        if (!c.moveToFirst()) {
            c.close();
        }
        return c;
    }

    /**
     * Performs a database query.
     * @param selection The selection clause
     * @param selectionArgs Selection arguments for "?" components in the selection
     * @return A Cursor over all rows matching the query
     */
    private Cursor query(String selection, String[] selectionArgs) {
        /* The SQLiteBuilder provides a map for all possible columns requested to
         * actual columns in the database, creating a simple column alias mechanism
         * by which the ContentProvider does not need to know the real column names
         */
        SQLiteQueryBuilder builder = new SQLiteQueryBuilder();
        SQLiteDatabase db = mDbHelper.getReadableDatabase();

        builder.setTables(QUOTES_TABLE_NAME);
        builder.setProjectionMap(mColumnMap);

        Cursor cursor = builder.query(db,
                null, selection, selectionArgs, null, null, null);

        if (!cursor.moveToFirst()) {
            cursor.close();
        }

        db.close();
        return cursor;
    }

    /**
     * Get a random quote
     * @param lang Filter by lang
     */
    public Cursor getRandomQuote(String lang) {
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
        qb.setTables(QUOTES_TABLE_NAME);
        qb.setProjectionMap(mColumnMap);

        qb.appendWhere("lang == ?");
        String[] whereArgs = new String[] { lang };

        Cursor c = qb.query(mDbHelper.getReadableDatabase(), null, null, whereArgs, null, null, "RANDOM()", "1");

        if (!c.moveToFirst()) {
            c.close();
        }
        return c;
    }

    /** Helps create and open the database file */
    private static class QuoteDbHelper extends SQLiteOpenHelper {

        private Context mContext;
        private boolean createDatabase = false;
        private boolean upgradeDatabase = false;

        QuoteDbHelper(Context context) {
            super(context, DB_NAME, null, DB_VERSION);
            mContext = context;
        }

        /** Db will be created later */
        @Override
        public void onCreate(SQLiteDatabase db) {
            Log.d("QOTD", "Database needs to be created");
            createDatabase = true;
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.d("QOTD", "Database needs to be upgraded");
            upgradeDatabase = true;
        }

        /** This method has to be called after constructor */
        public void initializeDatabase() {
            // Make sure we request database, to initialize creation variables
            getWritableDatabase();

            if (createDatabase) {
                copyDatabase();
            }
            else if (upgradeDatabase) {
                upgradeDatabase();
            }
            close();
        }

        /* To create database, we copy the one provided in assets */
        public void copyDatabase() {
            Log.d("QOTD", "Creating database");

            // We need to close the db handle to overwrite the newly created db
            close();

            try {
                // Fixtures db is in assets
                InputStream myInput = mContext.getAssets().open(DB_NAME + DB_FILE_FAKE_EXTEN);

                //Open the empty db as the output stream
                String outFileName = mContext.getDatabasePath(DB_NAME).getAbsolutePath();
                OutputStream myOutput = new FileOutputStream(outFileName);

                //transfer bytes from the inputfile to the outputfile
                byte[] buffer = new byte[1024];
                int length;
                while ((length = myInput.read(buffer)) > 0) {
                    myOutput.write(buffer, 0, length);
                }

                myOutput.flush();
                myOutput.close();
                myInput.close();

                // Access the db to set the access timestamp (prevents a "corrupted" error)
                getWritableDatabase();
                close();
            } catch (IOException ioe) {
                Log.e("QOTD", "Cannot create db : " + ioe.getMessage());
            }
        }

        /** Just wipe out the current db, and replace it with the fixture's one */
        public void upgradeDatabase() {
            Log.d("QOTD", "Updating database.");
            copyDatabase();
        }
    }
}

Java Source Code List

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