Android:Copy database in assets folder null pointer exception

I have read almost all the topics related to my problem in here so please do not say it is duplicate or has been questioned before.

I created the tables and the database in Sqlite Expert Personal 3. I copied it in assets folder. Right now I want to tell the android to check if there isnt already a database, copy the database from assets folder. so I do this:

datasource = new DataSource(this);
    List<Prayer> prayers = datasource.findAllPrayers();

    if (prayers.size == 0)
    {
        dbopenhelper.copyDataBase();
    }
    datasource.open();

Here it should check if there is any row at the table "prayers" and if there wasn't any rows, it should copy the database. but when I run the program, I get nullPointerException.

Here is my findAllPrayers() method which is in datasource class:

public List<Prayer> findAllPrayers()
{

    List<Prayer> prayerlist = new ArrayList<Prayer>();
    //
    Cursor cursor = database.query(DBOpenHelper.TABLE_PRAYER,
            allPrayerColumns, null, null, null, null, null);
    //
    Log.i(LOGTAG, "Child Cursor returned " + cursor.getCount() + " row(s).");

    if (cursor.getCount() > 0)
    {

        while (cursor.moveToNext())
        {

            Prayer p = new Prayer();
            p.setPrayer_name(cursor.getString(cursor
                    .getColumnIndex(DBOpenHelper.COLUMN_PRAYER_NAME)));

            p.setPrayer_ID(cursor.getLong(cursor
                    .getColumnIndex(DBOpenHelper.COLUMN_PRAYER_ID)));
            p.setPrayer(cursor.getString(cursor
                    .getColumnIndex(DBOpenHelper.COLUMN_PRAYER)));

            prayerlist.add(p);
        }
    }

    return prayerlist;

}

---

And here is my OpenHelper class:

package org.bihe.database;

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

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

public class DBOpenHelper extends SQLiteOpenHelper
{

    public static final String LOGTAG = "PRAYERBOOK_APP";
    //
    private static Context context;
    //
    private static String DB_PATH;
    //
    public static final String DATABASE_NAME = "Prayers.db";
    public static final int DATABASE_VERSION = 1;
    // ***Tables***
    public static final String TABLE_PRAYERTOPIC = "prayertopic";
    public static final String TABLE_PRAYER = "prayer";
    public static final String TABLE_FAVORITES = "favorites";
    public static final String TABLE_PRAYEROFTOPIC = "prayeroftopic";
    public static final String TABLE_FAVORITEPRAYERS = "favoriteprayers";
    public static final String TABLE_AUDIOPRAYERS = "audioprayers";
    // ***Table prayertopic columns***
    public static final String COLUMN_PRAYERTOPIC_ID = "prayertopic_ID";
    public static final String COLUMN_PRAYERTOPIC_NAME = "prayertopic_name";
    // ***Table prayer columns***
    public static final String COLUMN_PRAYER_ID = "prayer_ID";
    public static final String COLUMN_PRAYER_NAME = "prayer_name";
    public static final String COLUMN_PRAYER = "prayer";
    // ***Table favorites columns***
    public static final String COLUMN_FAVORITE_ID = "favorite_ID";
    public static final String COLUMN_FAVORITE_NAME = "favorite_name";
    // ***Table prayeroftopic columns***
    public static final String COLUMN_PRAYEROFTOPIC_ID = "prayeroftopic_ID";
    public static final String COLUMN_PRAYER_ID_POT = "prayer_ID";
    public static final String COLUMN_PRAYERTOPIC_ID_POT = "prayertopic_ID";
    // ***Table favoriteprayer columns***
    public static final String COLUMN_FAVORITEPRAYER_ID = "favoriteprayer_ID";
    public static final String COLUMN_FAVORITE_ID_FP = "favorite_ID";
    public static final String COLUMN_PRAYER_ID_FP = "prayer_ID";
    // ***Table auidioprayers***
    public static final String COLUMN_AUDIOPRAYER_ID = "audioprayer_ID";
    public static final String COLUMN_AUDIOPRAYER_NAME = "audioprayer_name";
    public static final String COLUMN_AUDIOPRAYER_ADDRESS = "audioprayer_address";

    // ***Creating Tables***
    private static final String CREATE_PRAYER_TABLE = "CREATE TABLE "
            + TABLE_PRAYER + " (" + COLUMN_PRAYER_ID
            + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_PRAYER_NAME
            + " TEXT, " + COLUMN_PRAYER + " TEXT " + ")";
    //
    private static final String CREATE_PRAYERTOPIC_TABLE = "CREATE TABLE "
            + TABLE_PRAYERTOPIC + " (" + COLUMN_PRAYERTOPIC_ID
            + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_PRAYERTOPIC_NAME
            + " TEXT" + ")";
    //
    private static final String CREATE_PRAYEROFTOPIC_TABLE = "CREATE TABLE "
            + TABLE_PRAYEROFTOPIC + " (" + COLUMN_PRAYEROFTOPIC_ID
            + " INTEGER PRIMARY KEY AUTOINCREMENT, " + " FOREIGN KEY("
            + COLUMN_PRAYER_ID_POT + ") REFERENCES " + TABLE_PRAYER + "("
            + COLUMN_PRAYER_ID + ") ON UPDATE CASCADE ON DELETE CASCADE "
            + " FOREIGN KEY(" + COLUMN_PRAYERTOPIC_ID_POT + ") REFERENCES "
            + TABLE_PRAYERTOPIC + "(" + COLUMN_PRAYERTOPIC_ID
            + ") ON UPDATE CASCADE ON DELETE CASCADE " + ") ";

    public DBOpenHelper(Context ctx)
    {
        super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
        context = ctx;
        DB_PATH = "/data/data/" + context.getPackageName() + "/" + "databases/";
    }

    //
    public static void copyDataBase()
    {
        try
        {
            InputStream input = context.getAssets().open(DATABASE_NAME);
            FileOutputStream output = new FileOutputStream(DB_PATH
                    + DATABASE_NAME);
            byte[] data = new byte[1024];
            int buffer;
            while ((buffer = input.read(data)) != -1)
            {
                output.write(data, 0, buffer);
            }
            output.flush();
            output.close();
            input.close();
        } catch (IOException ex)
        {
            Log.e(LOGTAG, "Error in copying database...");
        }
    }

    //

    // ***--***
    @Override
    public void onCreate(SQLiteDatabase db)
    {
        db.execSQL(CREATE_PRAYER_TABLE);
        Log.i(LOGTAG, "Table has been created");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
    {
        // db.execSQL("DROP TABLE IF EXISTS " + TABLE_PRAYER);
        onCreate(db);

    }

}

I would be very grateful if someone could tell me what is wrong with my code. THANKS IN ADVANCE