SQLiteOnSDCard.java :  » RSS » mobiledroidgis » mmenning » mobilegis » database » Android Open Source

/*
 * Copyright (C) 2010 by Mathias Menninghaus (mmenning (at) uos (dot) de)
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package mmenning.mobilegis.database;

import java.io.File;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Environment;

/**
 * Manages the Connection to a SQLITE Database on the SDCard. The Database will
 * be created in a folder named by the Applications package name.
 * 
 * @author Mathias Menninghaus
 * @version 23.10.2009
 */
public abstract class SQLiteOnSDCard {

  private static final String DT = "SQLiteOnSDCard";

  private static final String SDCARD = Environment.getExternalStorageDirectory().getAbsolutePath();

  private SQLiteDatabase db;

  /**
   * Connect to a SQLite Database with name name in the folder named by the
   * Contexts package name. If their is no such folder it will be created. If
   * their is no such database file a new one will be created an onCreate()
   * called.
   * 
   * @param context
   *            Context in which the SQLite database will be created.
   * @param name
   *            Name of the Database
   */
  public SQLiteOnSDCard(Context context, String name, int version) {
    db = null;
    
    String fullpath = SDCARD + File.separator + context.getPackageName()
        + File.separator + name;
    try {
      db = SQLiteDatabase.openDatabase(fullpath, null,
          SQLiteDatabase.OPEN_READWRITE);
      int oldVersion = db.getVersion();
      db.setVersion(version);
      if (oldVersion != version) {
        onUpgrade(db, oldVersion, version);
      }
    } catch (SQLException ex) {
      File path = new File(SDCARD + File.separator
          + context.getPackageName());
      if (!path.exists())
        path.mkdir();
      db = SQLiteDatabase.openOrCreateDatabase(fullpath, null);
      db.setVersion(version);
      onCreate(db);
    } finally {
      if (db != null) {
        db.close();
      }

    }
  }

  /**
   * Close the database connection if it is not closed yet.
   */
  public void close() {
    if (db != null && db.isOpen())
      db.close();
  }

  /**
   * Opens a readable database connection if it dois not exist yet.
   * 
   * @return readable SQLite database
   */
  public SQLiteDatabase getReadableDatabase() {
    if (db.isReadOnly() || !db.isOpen()) {
      db = SQLiteDatabase.openDatabase(db.getPath(), null,
          SQLiteDatabase.OPEN_READONLY);
    }
    return db;
  }

  /**
   * Opens a writable database connection if it does not exist yet.
   * 
   * @return writable SQLite database
   */
  public SQLiteDatabase getWritableDatabase() {
    if (db.isReadOnly() || !db.isOpen()) {
      db = SQLiteDatabase.openDatabase(db.getPath(), null,
          SQLiteDatabase.OPEN_READWRITE);
    }
    return db;
  }

  /**
   * Called on Version Changes
   * @param db SQLite database to change
   * @param oldVersion old database version
   * @param newVersion new database version
   */
  public abstract void onUpgrade(SQLiteDatabase db, int oldVersion,
      int newVersion);

  /**
   * Called when the Database is Created for the first time.
   * 
   * @param db
   *            the newly created Database
   */
  public abstract void onCreate(SQLiteDatabase db);

}