Android Open Source - grtransit Database Helper

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright 2011 Giles Malet.// w  w w . ja va2 s  .  c  o  m
 *
 * This file is part of GRTransit.
 * 
 * GRTransit 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.
 * 
 * GRTransit 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 GRTransit.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.kw.shrdlu.grtgtfs;

import android.app.AlertDialog;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.Environment;
import android.util.Log;

import java.io.File;

public class DatabaseHelper {
  private static final String TAG = "DatabaseHelper"; // getClass().getSimpleName();

  private static String DB_PATH = null;
  private static int DB_VERSION = -1;
  private static final String DB_NAME = "GRT.db";
    private static SQLiteDatabase DB = null;

  /**
   * Constructor takes and keeps a reference of the passed context in order to access the application assets and resources.
   */
  public DatabaseHelper(Context context) {

        // Fallback to old-style location if we're struggling....
    final String DB_OLD_PATH = context.getApplicationInfo().dataDir + "/databases/";

      // Returns something like
    // /mnt/sdcard/Android/data/net.kw.shrdlu.grtgtfs/files/
        File f = context.getExternalFilesDir(null);
        if (f != null) {
            DB_PATH = f.getPath();
        } else {
      DB_PATH = DB_OLD_PATH;
            f = new File(DB_PATH);
    }

    if (!f.exists() && !f.mkdirs()) {
      Log.e(TAG, "can't create sdcard dirs, using phone storage :-(");
      DB_PATH = DB_OLD_PATH;
    }
    if (f.exists() && !f.canWrite()) {
      Log.e(TAG, "can't write to sdcard dirs, using phone storage :-(");
      DB_PATH = DB_OLD_PATH;
    }

    // Delete the old database if it exists, and recreate on the sdcard.
    if (!DB_PATH.equals(DB_OLD_PATH)) {
      final File olddb = new File(DB_OLD_PATH + DB_NAME);
      if (olddb.exists() && !olddb.delete()) {
        Log.e(TAG, "failed to delete old db...!?");
      }

      // The database is on the sdcard.
      final String sdstate = Environment.getExternalStorageState();
      if (!sdstate.equals(Environment.MEDIA_MOUNTED)) {
        final AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle("The external database is unavailable.")
        .setMessage("The sdcard is in state `" + sdstate
            + "'.\nPlease retry when it is available.").create().show();
        return;
      }
    }

    // Do this once, as we don't need them separate anymore.
    DB_PATH += "/" + DB_NAME;
  }

  /* Return path to the database. */
  public static String GetDBPath()
  {
    return DB_PATH;
  }

  /* Force close the DB so we can recreate it */
  public static void CloseDB()
  {
    if (DB != null) {
      DB.close();
      DB = null;
    }
  }
  /* Return a handle for reading the database. */
  public static SQLiteDatabase ReadableDB() {

    if (DB == null) {
      try {
        DB = SQLiteDatabase.openDatabase(DB_PATH, null, SQLiteDatabase.OPEN_READONLY);

        // Stash the version
        final Cursor csr = DB.rawQuery("PRAGMA user_version", null);
        csr.moveToPosition(0);
        DB_VERSION = csr.getInt(0);
        csr.close();

      } catch (final SQLiteException e) {
        // bah
      }
    }

    return DB;
  }

  /* Return version of current DB */
  public static int GetDBVersion() {
    if (DB == null) {
      ReadableDB();
    }
    return DB_VERSION;
  }
}

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