We are using firebase realtime database and I was thinking about implementing a cache locally to reduce repeated calls.
So I came up with an algorithm which involves room persistence library.
stream only the latest data from firebase
store in room cache
when requested fetch all data from room cache and return
But then I started thinking about the cache that firebase provides and started realizing that I might be able to avoid room library at all.
stream only the latest data from firebase
when requested call fetch data using a singleValueListener
Since we are using single value listener only the cached data would be fetched from firebase.
What are the drawbacks of using the second approach? I know that firebase cache is limited to 10MB so that might be one
The one big thing you need to know here is that the cache managed by the SDK is almost fully outside your control. You can set the size of the cache, and you could clear it by trying to find the database file it uses, but otherwise, you can't configure it.
If you write code on your own, will have to make every decision about how it works, and it will be a lot of code to get everything right.
Unlike in Cloud Firestore, where offline persistence is enabled by default, in Firebase realtime database to enable offline capabilities you need to use the following line of code:
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
This means that you'll have by default a local copy of your database. So there is no need to add another one. So in this way you'll only get new data, otherwise everyhing is you get is from cache.
I am currently developing an application that provides some temporary static, but often changing data.
You can think of it like a telephone book. Most of the entries might never change, but there might be cases where people change their telephone number or move in/out. The dataset isnt large but has to be available at any time.
My first thought was to implement a clientside-SQLDatabase which queries a backend in certain intervals asking for updates (stored in another database on the backend server). If there was an update since the last query, the updated data will be send over and stored in the local sqldatabase.
Now I stumbled over this interesting looking database model Couchbase. Altough I dont see through it completly by now, if I got it, I can use it to keep the client-side database in sync with the servers database. Is this a usecase for couchbase or should I go with another strategy?
Thanks in advance!
That's a perfect use case for Couchbase. You'll want to check out Couchbase Lite (https://github.com/couchbase/couchbase-lite-android) and the Sync Gateway (http://docs.couchbase.com/sync-gateway/).
In Twitter Android App, Once the listview is populated with tweets/items downloaded from server, it never again talks to server to fetch them again. Even if you kill the app and start it again, it still retrieves the same old data.How does twitter store this much of data. Is it using database, storing all downloaded data in a file or caching.
In my app , i have a similar requirement.For now i store the downloaded listview data in a file and then read it whenever the app is started afresh.Is there a better approach or a followed patter for this.
Thank You.
There are three ways to save/persist data on clientside. These being:
SharedPreferences (not ideal with requirements)
File I/O
SQLLite database
As far as I know there isn't a big difference is performance between file-I/O and SQLLite. But SQLLite has a lot of other advantages.
You can query the database, this is more easy then writing it yourself with file-I/O
Manipulation of data is for more easy and less painful (delete/update records etc)
Supports relations between data!
Bottom line, go for SQLLite, it seems more work to setup but you will benefit from this in the future.
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
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I want to sync data (such as db record, media) between an Android App and a Server. If you've seen Evernote or similar Applications, you certainly understand what I mean.
I have some question (imagine we want to sync DB records):
Every user has a part of server space for himself (such as Evernote or Dropbox). Maybe the user creates new records by cellphone and creates new records in server. How can I match these records together? If there are records with same ID What algorithms do you suggest me?
Except JSON, Are there any way for send data between cellphone device and server?
If SyncAdapter and ContentProvider can solve my problems, please explain exactly for me. (If you could offer some samples or tutorials to me OR Any advice or keywords to help broaden/guide my search would be appreciated as well).
I'll try to answer all your questions by addressing the larger question: How can I sync data between a webserver and an android app?
Syncing data between your webserver and an android app requires a couple of different components on your android device.
Persistent Storage:
This is how your phone actually stores the data it receives from the webserver. One possible method for accomplishing this is writing your own custom ContentProvider backed by a Sqlite database. A decent tutorial for a content provider can be found here: http://thinkandroid.wordpress.com/2010/01/13/writing-your-own-contentprovider/
A ContentProvider defines a consistent interface to interact with your stored data. It could also allow other applications to interact with your data if you wanted. Behind your ContentProvider could be a Sqlite database, a Cache, or any arbitrary storage mechanism.
While I would certainly recommend using a ContentProvider with a Sqlite database you could use any java based storage mechanism you wanted.
Data Interchange Format:
This is the format you use to send the data between your webserver and your android app. The two most popular formats these days are XML and JSON. When choosing your format, you should think about what sort of serialization libraries are available. I know off-hand that there's a fantastic library for json serialization called gson: https://github.com/google/gson, although I'm sure similar libraries exist for XML.
Synchronization Service
You'll want some sort of asynchronous task which can get new data from your server and refresh the mobile content to reflect the content of the server. You'll also want to notify the server whenever you make local changes to content and want to reflect those changes. Android provides the SyncAdapter pattern as a way to easily solve this pattern. You'll need to register user accounts, and then Android will perform lots of magic for you, and allow you to automatically sync. Here's a good tutorial: http://www.c99.org/2010/01/23/writing-an-android-sync-provider-part-1/
As for how you identify if the records are the same, typically you'll create items with a unique id which you store both on the android device and the server. You can use that to make sure you're referring to the same reference. Furthermore, you can store column attributes like "updated_at" to make sure that you're always getting the freshest data, or you don't accidentally write over newly written data.
If we think about today, accepted answer is too old. As we know that we have many new libraries which can help you to make this types of application.
You should learn following topics that will helps you surely:
SyncAdapter: The sync adapter component in your app encapsulates the code for the tasks that transfer data between the device and a server. Based on the scheduling and triggers you provide in your app, the sync adapter framework runs the code in the sync adapter component.
Realm: Realm is a mobile database: a replacement for SQLite & Core Data.
Retrofit Type-safe HTTP client for Android and Java by Square, Inc. Must Learn a-smart-way-to-use-retrofit
And your sync logic for database like: How to sync SQLite database on Android phone with MySQL database on server?
Best Luck to all new learner. :)
If you write this yourself these are some of the points to keep in mind
Proper authentication between the device and the Sync Server
A sync protocol between the device and the server. It will usually go in 3 phases, authentication, data exchange, status exchange (which operations worked and which failed)
Pick your payload format. I suggest SyncML based XML mixed with JSON based format to represent the actual data. So SyncML for the protocol, and JSON for the actual data being exchanged. Using JSON Array while manipulating the data is always preferred as it is easy to access data using JSON Array.
Keeping track of data changes on both client and server. You can maintain a changelog of ids that change and pick them up during a sync session. Also, clear the changelog as the objects are successfully synchronized. You can also use a boolean variable to confirm the synchronization status, i.e. last time of sync. It will be helpful for end users to identify the time when last sync is done.
Need to have a way to communicate from the server to the device to start a sync session as data changes on the server. You can use C2DM or write your own persistent tcp based communication. The tcp approach is a lot seamless
A way to replicate data changes across multiple devices
And last but not the least, a way to detect and handle conflicts
Hope this helps as a good starting point.
#Grantismo provides a great explanation on the overall. If you wish to know who people are actually doing this things i suggest you to take a look at how google did for the Google IO App of 2014 (it's always worth taking a deep look at the source code of these apps that they release. There's a lot to learn from there).
Here's a blog post about it: http://android-developers.blogspot.com.br/2014/09/conference-data-sync-gcm-google-io.html
Essentially, on the application side: GCM for signalling, Sync Adapter for data fetching and talking properly with Content Provider that will make things persistent (yeah, it isolates the DB from direct access from other parts of the app).
Also, if you wish to take a look at the 2015's code: https://github.com/google/iosched
For example, you want to sync table todoTable from MySql to Sqlite
First, create one column name version (type INT) in todoTable for both Sqlite and MySql
Second, create a table name database_version with one column name currentVersion(INT)
In MySql, when you add a new item to todoTable or update item, you must upgrade the version of this item by +1 and also upgrade the currentVersion
In Android, when you want to sync (by manual press sync button or a service run with period time):
You will send the request with the Sqlite currentVersion (currently it is 1) to server.
Then in server, you find what item in MySql have version value greater than Sqlite currentVersion(1) then response to Android (in this example the item 3 with version 2 will response to Android)
In SQLite, you will add or update new item to todoTable and upgrade the currentVersion
Look at parseplatform.org.
it's opensource project.
(As well as you can go for commercial package available at back4app.com.)
It is a very straight forward and user friendly server side database service that gives a great android client side API
one way to accomplish this to have a server side application that waits for the data. The data can be sent using HttpRequest objects in Java or you can write your own TCP/IP data transfer utility. Data can be sent using JSON format or any other format that you think is suitable. Also data can be encrypted before sending to server if it contains sensitive information. All Server application have to do is just wait for HttpRequests to come in and parse the data and store it anywhere you want.
I would suggest using a binary webservice protocol similar to Hessian. It works very well and they do have a android implementation. It might be a little heavy but depends on the application you are building. Hope this helps.
#Grantismo gives a great overview of Android sync components.
SyncManagerAndroid library provides a simple 2-way sync implementation to plug into the Android Sync framework (AbstractThreadedSyncAdapter.OnPerformSync).
https://github.com/sschendel/SyncManagerAndroid