将数据传输到新的数据库版本android

我正在尝试编写一个函数，它将获取数据库中的当前信息，并使用onUpgrade方法将其放入新版本中。这就是我所拥有的

public void updateTable(SQLiteDatabase db) {
    Cursor c = db.rawQuery(
            "select DISTINCT tbl_name from sqlite_master where tbl_name = '"
                    + tableName + "'", null);
    if (c != null && c.getCount() > 0) {
        c = db.rawQuery("select * from " + tableName, null);
        ArrayList<Transaction> tempList = new ArrayList<Transaction>();
        while (c.moveToNext()) {
            Transaction t = createTransaction(c);
            if (t != null)
                tempList.add(t);
        }
        dropTable(db);
        createTable(db);
        for (Transaction t : tempList) {
            addOccurrence(t);
        }
    } else {
        throw new RuntimeException("Couldn't find new table for updating");
    }
}

问题是，我从onUpgrade方法获得的数据库中没有任何内容！所以我只是删除了我的数据库。。。。有没有办法做到这一点，或者我必须依赖ALTER语句的有限使用。谢谢

public void onUpgrade(SQLiteDatabase new_db, int oldVersion,
                int newVersion) {
            // TODO Auto-generated method stub
            System.out.println("onUpgrade()");
            new_db.execSQL("DROP TABLE IF EXISTS " + TableName + ";");
            onCreate(new_db);
        }

public void onUpgrade(SQLiteDatabase new_db, int oldVersion,
                int newVersion) {
            // TODO Auto-generated method stub
            System.out.println("onUpgrade()");
            new_db.execSQL("DROP TABLE IF EXISTS " + TableName + ";");
            onCreate(new_db);
        }