DatabaseHelper.java

package it.fdev.unisaconnect.data;

import it.fdev.utils.Utils;

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.preference.PreferenceManager;
import android.util.Log;

public class DatabaseHelper {

    private String databaseName;
    private static final int DATABASE_VERSION = 3;
    private String SP_KEY_DB_VER = "db_ver";
    private final Context mContext;

    public DatabaseHelper(Context context, String databaseName) {
    	this.databaseName = databaseName;
    	SP_KEY_DB_VER += databaseName;
        mContext = context;
        initialize();
    }

    /**
     * Initializes database. Creates database if doesn't exist.
     */
    private void initialize() {
        if (databaseExists()) {
            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
            int dbVersion = prefs.getInt(SP_KEY_DB_VER, 1);
            if (DATABASE_VERSION != dbVersion) {
            	Log.d(Utils.TAG, "Database "+ databaseName +" will be updated");
                File dbFile = mContext.getDatabasePath(databaseName);
                if (!dbFile.delete()) {
                    Log.w(Utils.TAG, "Unable to update database "+ databaseName);
                }
            }
        }
        if (!databaseExists()) {
            createDatabase();
        }
    }

    /**
     * Returns true if database file exists, false otherwise.
     * @return
     */
    private boolean databaseExists() {
        File dbFile = mContext.getDatabasePath(databaseName);
        return dbFile.exists();
    }

    /**
     * Creates database by copying it from assets directory.
     */
    private void createDatabase() {
        String parentPath = mContext.getDatabasePath(databaseName).getParent();
        String path = mContext.getDatabasePath(databaseName).getPath();

        File file = new File(parentPath);
        if (!file.exists()) {
            if (!file.mkdir()) {
                Log.w(Utils.TAG, "Unable to create database directory for: "+ databaseName);
                return;
            }
        }

        InputStream is = null;
        OutputStream os = null;
        try {
            is = mContext.getAssets().open(databaseName);
            os = new FileOutputStream(path);

            byte[] buffer = new byte[1024];
            int length;
            while ((length = is.read(buffer)) > 0) {
                os.write(buffer, 0, length);
            }
            os.flush();
            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
            SharedPreferences.Editor editor = prefs.edit();
            editor.putInt(SP_KEY_DB_VER, DATABASE_VERSION);
            editor.commit();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}