How to properly sync chat messages in offline/online mode?

Question

Help me in designing a better solution to sync chat messages between a single app user and server. If an app goes offline, i want to store messages in app database and push them to server when internet is available. And if at same time someone sends user a message, i want to properly arrange them based on time stamps. But are time tamps reliable in this scenario?

Answer 1

Yes timestamps are reliable. But make sure you dont update the timestamps when a message that was in pending queue is sent.

A way to look forward to this is creating a broadcast manager and since you already have an app-db things can be easy.

Step 1: Create a BroadCastReceiver to listen for network changes

A good SO post for the same can be found here where <action android:name="android.net.conn.CONNECTIVITY_CHANGE" /> is used to detect connectivity changes.

Step 2: Create int flags for your messages:

Where: assume: int

0 -> unsent

1-> sent

2-> read etc...

So whenever the user sends the message, check for the internet connectivity using this and if internet is not avail store to your app-local db with flag->0 else post to server

if you get a positive callback from the server save it as flag->1 else again with 0.

Step 3: Now in your onRecieve method of your broadcast receiver, check if the changed status is a connected one (as in network connection is established) then pull from your db all messages which are saved with flag ->0 and resend them to the server with again the validations checks in step 2: just make sure you update them this time instead of recreating a new entry!

And that should be it!