I am very new to android and am trying to understand db persistence.
Consider this scenario
on device1 local db created
it syncs with google via the BackupAgent by backing up the db file
on device2 db file is restored and local db is now in sync
The problem I think I may have what happens if there is no remote connection. Then this could happen
on device1 local db created
it syncs with google via the BackupAgent by backing up the db file
on device2 previous db file is updated offline
device2 goes online. Syncs with backup agent and device2 changes are lost
There are various scenarios where I think this pattern will cause conflicts between devices. Am I missing a simpler better way to store and sync data between multiple devices. Perhaps just only store things on a remote databse perhaps.
As i said I am new to this so any advice would be greatly received.
Thanks
From the docs:
The backup service is not designed for synchronizing application data with other clients or saving data that you'd like to access during the normal application lifecycle. You cannot read or write backup data on demand and cannot access it in any way other than through the APIs provided by the Backup Manager.
The backup agent is not meant to be used in the way you are using it. It is not meant to provide real-time syncing of data between multiple client devices. It is only designed to backup stuff such as user preferences so that if users move to a new device or reset their phones, they can restore their settings and things like that .
When you request a backup, the agent does not do it immediately. It does it at a later time based on a number of different parameters (such as network efficiency). It is generally meant to store the latest version of a users preferences.
If you want real-time syncing between devices, you would need to implement your own backend or try out one of the BAAS (Backend-As-A-Service) providers such as Parse or Firebase.
Related
From this site: https://developer.android.com/training/data-storage/room
".. The most common use case is to cache relevant pieces of data. That way, when the device cannot access the network, the user can still browse that content while they are offline. Any user-initiated content changes are then synced to the server after the device is back online."
Why is rooming trying to access the network, when the data is stored locally as Room is a local database?
That description seems wrong or do I misunderstand something?
Room doesn't require network access.
That is just giving an example of a situation where SQLite (and therefore Room) can be useful as SQlite is an embedded database. That is if the App gets data via the network but the device may not always have access then some data can be stored locally on the device freeing it from permenant newtwork access.
It is quite feasible to have Apps that use Room that have no network access at all. In which case the data would either be input by the device's user or perhaps distributed via the APK.
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 am planning to switch to Firebase as my local and online database for my Android app. As per the docs, Firebase stores changes to the local database first and then pushed it to the online DB when network is available.
In my app, I would be putting some really sensitive data about the user in the database. So here are my questions,
How secure is the local Firebase database?
How difficult is it for a well-intentioned hacker with the right tools to hack it?
Is it just a simple JSON file like the online database, which anyone with root access can open?
Thanks.
In a general sense, Firebase Realtime Database can be used while offline. However, the expectation is that the app is supposed to be connected most of the time, and changes to the database that happen while offline will be synchronized when it has connectivity. 100% offline use is not really a supported use case, because the canonical data store is on the server.
The local copy of the database is limited to (10MB, at least on Android this is the case). If you intend to write to the database beyond this limit while offline, it will evict part of your cached data to make room for whatever you’re adding. Then, you will no longer be able to read those evicted values until the app goes back online. Worse, managing a growing list of writes to apply when back online is taxing on the app, so you don’t want to plan a lot of writes while offline.
Also, if you have permissions or validations defined for your database, these can only be checked on the server. So, if you’re doing offline writing to your local cache and you no longer have an active listener, you may never know if those writes fail.
Because of these caveats, it’s better not to think of Firebase Realtime Database as an “offline” database. It’s better to think of it as a “synchronized” database that actively syncs to the server while connectivity is present.
I'd like to make a basic to do app in android to get my feet wet. I have a rest api and online DB that handles the basic CRUD when there is a connection present.
Most task apps I've used however, allow creating tasks when there is no connection present.
What are the best practices for stuff like this?
Do apps usually store a copy of ALL data for a user locally so there is access to it when a connection is not present?
It looks like the app I use (astrid tasks) has no problem accessing all my tasks/history regardless of connection
If this is the case, how is syncing handled as far as the remote data's primary keys are concerned?
You have some encoding, let say one request per single data change to be executed atomically encoded as xml or json. Make a base class which is parent of connection and use it to send data update to remote db. If connection isn't present store entire command into file or sqlite. You can create multiple files (if going by file approach) based on their sizes, date etc. Create some rules how the oldest record will be chosen - if you need to update db in ordered manner.
One solution would be to have a local database in your application. When there's no internet connection store the data in this database.
Now let your application listen for network changes. When the device is connected to the network, you could upload the cached data from local database to the server without user interaction.
In my app I have a SQLite DB want to backup to server but what I want is one to one synchronization for off-line backup (e.g. standalone SQLite file instead of a centralized MySQL server, mainly performance reason and I don't need real time query)
Ideally I don't want to upload the database everytime when I need to sync, prefer only sync the changes?
Are there any existing solution for this? (I can consider using other file DB as currently I mainly use SQLite as Key-Value database)
Thanks.
As you are willing to consider using a different DB, take a look at TouchDB-Android. This syncs a database on an Android device to a CouchDB server. There is a related project SyncPoint, that automates setting up a database for each user.
We are using TouchDb-iOS for our product at the moment are planning work on an Android version using TouchDB-Android soon.
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