Where does Room store the database and how can I force a rebuild of the DB? I've tried looking for the DB under:
data/data/com.me.myapp/No database directory here
data/user/0/com.me.myapp/No database directory here
I want to see exactly what data is in the database using SQLLite so I followed these directions "Access database in Android Studio" but I only see a cache and codecache directory stored there. No database directory.
The reason for wanting to see the DB is that I changed the model to add a few fields, but I can't figure out how to force Room to recreate and repopulate the DB with data. I added breakpoints inside my data generator class; however they don't seem to ever get hit.
if you change your entities structure (aka add fields) then in order not to loose data and get the fields added when user updates the current version of the app you need to implement migration . See the docs how to do it. So updating the app version will make your db "rebuild" and not lose data. When I just work with test version I delete app and build it on device again it'll implement the changes in db structure but you'll lose the data.
You should definitively see db files in the directories you named.
If you want some other method to debug a database you could use this library git link
Related
This is my first time working on a Xamarin App and I am new to the app development world so I need some help figuring out this process.
Currently I run a php web service that generates some SQL files that I run in DB Browser and I get a database file which I then put into my Assets and Resources Folder. Using each platform's API I copy the database into a writable folder and use that to run my queries.
I followed this really helpful tutorial and it worked perfectly fine.
https://medium.com/#hameedkunkanoor/creating-a-sqlite-databse-and-storing-your-data-in-your-android-and-ios-application-in-xamarin-2ebaa79cdff0 .
After the "initial" setup I store a timestamp in a local table and and the next time the user opens the app I pass that timestamp and retrieve data that is older than that timestamp. The I update that timestamp and continue the process. That data is sent back in JSON format and make the updates to the tables.
My only concern is if a new version were to come out where I add a new table or a new column which is not present in the current version of my Database, how should I take care of those update Web Service calls? Is there a way of monitoring my DB version? I read somewhere where I could just ignore the new data that is not present already, like table or columns, but I'm not really sure how to do that.
I also saw that if I call CreateTable on my current tables I could potentially update them?
Also for future reference each time I develop a new app would I need to regenerate a new database file to store in the assets/resources folder? Is there a more automated process for this? Along with monitoring the version of my database?
Any Help/Tutorials/Suggestions would be greatly appreciated.
You have to remember that CreateTable it's already doing the columns update for you, because internally it calls a method called MigrateTable which you can see here for further clarification: https://github.com/praeclarum/sqlite-net/blob/master/src/SQLite.cs#L562.
However you could have to handle more advanced modification to your database, like adding triggers or something similar.
In that case i suggest you to perform modifications manually.
In Xamarin Forms i've ended up with this:
https://gist.github.com/matpag/b2545cc22c8e22449cd7eaf6b4910396
Could not be the best strategy ever but seems to work for me.
Summarizing :
You have to save the database version in an internal flag of the SQlite database called user_version accessible with PRAGMA keyword.
Every time you get the database connection, you have to perform a check and see if the current database version is the same as the app last database version.
If not you need to perform a database update and set the new current version.
Reference here.
I have an android application that relies on a sqlite database, and use OrmLite to access my DB.
Instead of OrmLite creating the tables I rely on downloading the database from a central server as the user will often want to "sync" things. Currently I don't have the fancy sync code written so the app replaces the db. The steps are:
1 Download the latest SQLite db file from the server, as a zip
2 Expand the file to produce a database.sqlite file in a temporary folder
3 Deletes the contents of a data folder, which contains the live database.sqlite file
4 Move the database.sqlite file from the temporary folder to the data folder.
The problem is that the new database file seems to get ignored and DAO queries I run return old data. The only way to show data from the new version of the DB is to restart the application.
To test things I created a table with a timestamp that records when the database was generated, each time you request a new copy of the sqlite db from the server this is updated. I have a fragment that displays this time so you know how fresh your data is. In the fragments onResume method I make a call to the DAO to get the timestamp and put value on screen. I've stepped through this and I see the call to the DAO but the value that comes back is from the old, now deleted, db. Restart the app and the correct value is shown.
So my question is, if I replace the underlying sqlite db file that stores my database, how can I tell ormlite to pick it up or refresh the connection or whatever it has to do???
I tried calling clearObjectCache on the DAO, made no difference.
I'm new to programing for android and i'm still learning. So I have a question about the location of the SQLite database. Is it stored in the same file system as the application ?
And also i'm not sure can the database be created before the app is installed(can it come with the app) or can the database only be created from inside the app ?
And what if i wanted my app to come with a database that already has tables and records which is local and not on a server. Would that be possible ?
SQLite is available on every Android device. Using an SQLite database in Android does not require any database setup or administration.
You only have to define the SQL statements for creating and updating the database. Afterwards the database is automatically managed for you by the Android platform.
Access to an SQLite database involves accessing the filesystem. This can be slow. Therefore it is recommended to perform database operations asynchronously, for example inside the AsyncTask class.
If your application creates a database, this database is by default saved in the directory DATA/data/APP_NAME/databases/FILENAME.
The parts of the above directory are constructed based on the following rules. DATA is the path which the Environment.getDataDirectory() method returns. APP_NAME is your application name. FILENAME is the name you specify in your application code for the database.
You can also follow this tutorial for further understanding.
http://www.androidhive.info/2011/11/android-sqlite-database-tutorial/
Database is created after the app installation or after the db changes. The db is stored in /data/data/your_package/databases/
I have Database in my application which is created by just coping the SQLite database file from the assets folder but now in the next release I want to update the database without losing the previous data.
Is there any Logic or way to copy the previous data and create a new database through SQLiteOpenHelper so that in near future I will not face this problem.
Thanks
Use this gist
In the OnUpgrade method, copy your previous data from the old database.
In the doUpgrade method, use your copied data to update the new database.
Previous data will be kept by default when users update to a new version. but you must keep in mind there will be new users never get a former version app. So you should add complete database in the assets folder.
I have an SQLite database for my Android app that stores a copy of some data from another database on a server. When the user opens the app, I want to sync the local copy to the external master. The user may have been on the related website and inserted/updated/deleted data.
If it was just insert/update, timestamps could be used, but as they could delete data, I'm not sure how to go about checking for deleted rows.
So, what's the best way to tell what's changed and update the local copy?
I'd add a table to audit the deletes (containing key fields of the deleted records) and transfer that on sync, and after a successful sync clear the table down.
Hm, we are working on iOS project, which will sync it's database with server if server will respond what it have newer version.
Our server incrementally stores performed SQL and on request if compounds all those changes to specific date and gziped sends to the application, where my Objective-C wrapper execute SQL statement from downloaded file.
May be same approach will be good for you too.