I want to build a fairly simple Android application.
The basic data model of my app consist on several basic elements with relationships between them.
I want the data to be persistant so I'm thinking about using an sqlite DB.
I looked at the Android Developer website, and the closest thing that I could find that is relevant to my question is the "NotePad Tutorial" which make use of an sqlite DB to store notes.
I think by now I got the handle on the basics, but I still have some questions though:
In the tutorial they have only one table in the DB. If my application requires a more complicated scheme - should I still use the same method? that is - putting everything inside a subclass of SQLiteOpenHelper? Or is there a more "structured" way to go?
Should I bother creating classes for all the data elements stored in my DB? I mean this is what I learned that I should do, but in the documentation there is no hint about that.
If I Should create classes - How should I use them correctly? I mean, since the result of the query is a Cursor object, and not a collection of rows, Should/Can I parse that into objects?
Thanks!
Define all the tables in the same subclass, this makes easy to see all the table at one place and possibly write SQL for upgade etc
Yes, that would be easier for manipulation in the java side and makes code clean
Read from the cursor and initialize an arraylist of objects one by one.
Related
I want to store a little bit of data on my server that can be accessed easily by anyone. It's for a game I am making and I want to store a few things such as:
Game version (String)
Description (Long String)
News (Array of Strings)
Changelog (Array of Strings)
etc...
I figured that making a whole database and table for this would be overkill. I would like to be able to access the information using various types of media but I at least ant it to work with PHP (web) and Java (Desktop and android). Also the data will be updated and inputted manually by only me but readable publicly so that other websites can use it if they choose. What would I use for this kind of thing?
Extra: I might eventually want to input data manually. Things such as "Players Joined" would be managed by my server and would increment it automatically.So if it can do that too that would be great.
I have decided to use a Database and access the data with MySQL. I already have one for my game so it is a good choice because of that (this means I won't be creating a whole database just for this). I will create a table that will store this data and the table will only have 1 row (ID = 0). I will access it by selecting the row with ID = 0. I will have to create other tables with news and changelogs too.
If you have a similar question to mine, check this out:
http://www.dummies.com/how-to/content/storing-data-with-php-flat-file-or-database.html
It provided some useful advice. Also look into JSON or XML and SQLite.
You might want to check out H2 database. It can run as an embedded database (just include a jar, no extra installation, etc.), is very solid and you can get up and running very quickly.
I am planning on creating an android application sometime in the future in which I'll want it to display a lot of constant data on the screen.
I'm not sure the best way to do this but I see two options:
Storing the data within the code itself such as creating a constants class.
Using an embedded database to hold the data.
I'm guessing option #2 is the best way? But it just seems weird using a database if I'm not going to be doing any updating to the database, I would only be selecting.
The total amount of data that I need the application to display is maybe about 400 lines consisting of a string and two integers...
Is there a different way people use for such a situation that I don't know about?
But it just seems weird using a database if I'm not going to be doing
any updating to the database
I am totally disagree with you. Database is not only for updating. It can be used as a better storage and definitely a best way for searching. So as you want to preserve the data then it is definitely wise to use database.
But if you want to handle data which will not persists , i,e you will use different datas for different run then you can use temporary class or other data structure to store data.
Finally, If you are planning to have portability then File storage is an easier solution.
SO you can see, that it totally depends on what you want.
I´m a bit confused as to why there is no widely proposed model of storing your SQLite database structure in Android. Surely it would be nothing but advantageous to keep your column and table names somewhere central for reference, keeping you from going through your entire project when the database changes in structure. How are you handling this? I was thinking of creating a seperate class file called DatabaseConstants with the entire structure in static strings, but I would like to know if there is a better way?
Thanks for your time.
You can look at the ContactsContract for example to see the column names for Android Contacts.
I am making a java desktop application for billing customers that will be using a mysql database (so I can make a php frontend using the same database later). I was wondering if I should make a class that puts all the mysql info into arrays on startup so I can work with the arrays or if I should just query the database when I need to access data.
I was wondering what is the most efficient, fastest etc... Has anyone got an good pointers?
You should query the database when you need the data. That's what databases are for. If you bring all the data into Java arrays, then you will end up building querying methods on those arrays, or limiting yourself to simplistic ways of accessing the data.
If your data is small enough to fit easily into RAM, then MySQL will cache it all anyway, and it will go just as fast as if you had pulled it into arrays first.
Putting data into arrays might make sense if it's static - I'd call that caching.
But billing data seems more dynamic to me, depending on how you define it. In that case, I'd query the database each time.
Query as needed rather than pre-loading all the information. This will use potentially a lot less memory. Some of your data may need to be cached while working, but odds are most of it doesn't. The RDBMS is already designed and optimized to store and retrieve data as needed, so it is best allowed to do its job.
For a university assignment I have been assigned I have a Prize object which contains either text, image, or video content. I would like to persist this information into a BLOB field within an Apache Derby database (which will be running on a low powered PDA). How can I add this data to the database?
Thanks in advance.
In this article Five Steps to Managing Unstructured Data with Derby
you can read how to do this.
It describes how to insert binary data into a column with the BLOB datatype in Apache Derby using JDBC.
I assume you'll be connecting via JDBC. If so, simply write your SQL and look at the setBlob method of a PreparedStatement. Should be pretty straightforward.
Serialization is the easy way to do it, however if possible you could make it look like a real database table with a structure containing id (bigint), datatype (smallint), creationdate (date) and data (blob) and specifically make the client code to save the object's data there. This way you could do searches like "get all video prizes created between January 1st 2008 and January 15th 2009" and it wouldn't break down old data if your class would change too much for the serialization to stop working.
This sort of solution would be easy to extend in the future too if there would be need for it; I understand this is a school assignment and such need most likely won't ever surface but if your teacher/professor knows his stuff, I bet he's willing to give an extra point or two for doing this excercise in this way since it takes a bit more time and shows that you can take the steps to prepare in advance for coping in the everchanging landscape of software development.
If you are using Netbeans (I assume Eclipse has similar functionality) you can setup your database schema and the create new Java entity classes from the database and it will generate the appropriate JPA classes for you.
http://hendrosteven.wordpress.com/2008/03/06/simple-jpa-application-with-netbeans/
This is nice as it allows you to focus on your code rather than the database glue code.
The best solution , is to use Derby, because it keep being a multi platform app developed via Java.