Android Open Source - BusFollower Database Helper

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright 2012-2014 Clayton Smith//w w  w . ja  va  2 s.  c o  m
 *
 * This file is part of Ottawa Bus Follower.
 *
 * Ottawa Bus Follower 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, or (at
 * your option) any later version.
 *
 * Ottawa Bus Follower 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 Ottawa Bus Follower; see the file COPYING.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

package net.argilo.busfollower.ocdata;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.content.SharedPreferences;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.util.Log;

public class DatabaseHelper {
    private static final String TAG = "DatabaseHelper";
    private static final String DATABASE_PREFS = "DbPrefsFile";
    private static final int DATABASE_VERSION = 16; // Increment this whenever the DB is changed

    Context context;
    private final String DATABASE_FOLDER;
    private final String DATABASE_PATH;
    
    public DatabaseHelper(Context context) {
        this.context = context;
        String filesDir = context.getFilesDir().getPath();
        DATABASE_FOLDER = filesDir.substring(0, filesDir.lastIndexOf("/")) + "/databases";
        DATABASE_PATH = DATABASE_FOLDER + "/db";
    }
    
    public SQLiteDatabase getReadableDatabase() throws SQLiteException {
        try {
            writeDatabaseIfNecessary();
        } catch (IOException e) {
            throw new SQLiteException("Couldn't write database file.");
        }
        return SQLiteDatabase.openDatabase(DATABASE_PATH, null, SQLiteDatabase.OPEN_READONLY);
    }

    private void writeDatabaseIfNecessary() throws IOException {
        File folder = new File(DATABASE_FOLDER);
        if (!folder.exists()) {
            if (!folder.mkdir()) {
                throw new IOException("Couldn't create folder " + DATABASE_FOLDER);
            }
        }
        
        SharedPreferences dbPrefs = context.getSharedPreferences(DATABASE_PREFS, Context.MODE_PRIVATE);
        int dbVersion = dbPrefs.getInt("dbVersion", 0);
        
        if (dbVersion != DATABASE_VERSION) {
            Log.d(TAG, "Attempting to write database file.");
            InputStream is = context.getAssets().open("db");

            // Copy the database into the destination
            OutputStream os = new FileOutputStream(new File(DATABASE_PATH));
            byte[] buffer = new byte[1024];
            int length;
            while ((length = is.read(buffer)) > 0) {
                os.write(buffer, 0, length);
            }
            os.flush();

            os.close();
            is.close();
            Log.d(TAG, "Successfully wrote database file.");
            
            SharedPreferences.Editor editor = dbPrefs.edit();
            editor.putInt("dbVersion", DATABASE_VERSION);
            editor.commit();
            Log.d(TAG, "Wrote new database version number to preferences file.");
        }
    }
}

Java Source Code List

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