I there a way I can set up my app so that things like the database and images can be optionally downloaded/updated when when I make changes to the data, without updating the app. i.e. a kind of syncing with the new data?
I would have the database and images on my server and the user can update or not without having an icon on their phone saying there are updates available.
As far as I know, Android databases are just sqlite.db files. You should be able to have a button in your app that downloads a new sqlite.db file from your server. Have it replace the file that is already on the device and you should be good to go!
If you have a localized database you can modify, add to, and delete as needed based on server response. Create a robust enough Database Helper and you can use it to make the database whatever is needed, in a run time environment.
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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'd like to receive some advice from all of you.
What is the best way for me to alert users on an update to my app? My app is a very knowledge-based & it works like a dictionary, so there will always be updates to it.
The database I have used is by DB Browser for SQLite, and they are all local database where it is uploaded into the assets folder in Android Studio.
Currently, the limitations are that:
1) it's obviously not real-time because it's stored locally;
2) every update I make to the database structure, I am required to upload the new database into the assets folder again, followed by uninstalling the old app on my phone, then run the app to install in my phone again so that the new database is overwritten.
I have read (How can I regularly update a database of content on an Android app?) & some others, and it seemed like I have to have a server, a cloud-based database & live app in market, to solve the limitations?
Is there really no way for me to overcome the limitations if I want to stick to a local database? At the same time, I kinda wish to avoid setting up a server because I am not intending to make the app live on market, and also this is just a school project I am working on and as such, I have very limited skill sets & knowledge about it and would like to make it on a school-project-based level.
Thanks in advance.
One way to do it is to connect to your local DB through local network instead of assets folder. Therefore, you can update the information by querying the local DB.
As for syncing the information between DB and your application, you should create a trigger or watcher that notify your application when the DB is updated. Therefore, your application can know when to query the DB for the updates. Another way is to just query the database periodically.
Bonus: you could move your database to a cloud-based database. Usually there are several providers that provide free database hosting up to a certain size, which should be enough for your project.
I have started working with databases lately, I was able to create a local database and manage it in my Android app. Now I want to move to higher level with it but I don't know how to do it.
The users in my app need to be able to modify the database, for example insert new data in it. When a user insert new data in the database I want other users to see this change in their copy of the database.
I understand that I will need to store that database on a server or something and synchronize it with the users.
Can anyone tell me the steps to do so?
You should perfom this task in steps.
First, make the local database, and use a system to know when/what changed.
I usually work with triggers myself, but any "mark" is enough to synchronize.
Then, you must make a replica of that database somewhere else. Realise that maintaining the databases is a process, any change in the structure of one database must be performed in all other as well.
Finally, you must implement a method to transfer the data.
So, for an example:
db_local the database in the device.
db_outside the database in the internet.
db_local.trigger -> onInsert
On the applications, check for internet, then connect to your server, then upload the same command to db_outside and run it...
In this step, you must handle connection issues, and if the SQL command was succesfully executed, you have replicated the database content.
Once you have the replicated database, inform a system (like google cloud messaging), that the database was changed, and have the other users pull the info.
I have an online (postgresql) database, and a local copy of the db in an Android app. The data in these is synchronized, so the app can function offline, but can download new data and upload results when it can. Data is transfered via http GET and POST requests.
I have no problem synchronizing the data for known tables, however, I would like it to be possible to create new tables/alter tables in the online database and have that change reflected in the Android db automatically i.e. without having to release a new version with the updated synchronization code. Is there an obvious/standard way to do this that I haven't found? Google searches I have performed just refer to database migrations for two of the same system or for known schema.
Is there an obvious/standard way to do this that I haven't found?
There's no "standard" way but there are ways to do it depending on your requirements and how your app works.
It's actually a broad question but solvable if you give it a bit of thought.
My app downloads data from a server on a daily basis. Part of the download process involves downloading a DB version file (just a plain text file) similar to the following...
db_version=12345
...the string representation of the previous version (if any) is saved in SharedPreferences as an int value.
If the version in the file is greater than the one in SharedPreferences, the downloader pulls some text files which contain SQL commands for creating, dropping, altering tables etc. Only after the changes have been successfully made does the downloader pull the actual data files and update the DB data (not forgetting to update the latest version in SharedPreferences).
If the version in the file is the same as in SharedPreferences then obviously the download simply does the normal daily data download and DB data update.
I am developing an app in which i would need a local database.
So as per my knowledge there are two ways to do it:
First is to add pre filled database file in assets folder & make copy of local database from it the very first time app is started.
Second is using script to download it from Server for first time of app use?
First way have been pretty well answered by this guy Using your own sqlite database in android application
Can someone help how can i go with second way of download data from Server?
Should i use JSON/XML for getting that data from my Server?
Or should i go with first option since my app has only around 150 to 200 rows in the db file?
Go for the local db for the following reasons:
The users would have great on boarding experience as they can very quickly start seeing the utility of the app since you provide some data on first run without any delay that might be added when you fetch data from the server.
Do it for sure if the db doesn't increase the apk size significantly.
You must use php only if you need get information from the server, with php and json is better ...
http://www.vogella.com/articles/AndroidJSON/article.html
and if you only need share local information, only needs use MYsqLite ...
http://www.vogella.com/articles/AndroidSQLite/article.html