I am unable to figure this out. I have scenario, I am getting the video data in background via viewModel, coroutine and result in LiveData. The call to viewModel happens in onViewCreated of fragment. And in onResume I initialise ExoPlayer.

Now if I get the livedata result before onResume has completed and call play() by passing the videoUrl it would fail as ExoPlayer is not initialised yet.

How do I sync up this ?

And this are the 2 known solutions. 
a) init ExoPlayer instance after receive data, b) invoke ViewModel after init ExoPlayer.

But that's the recommended one by google itself in their sample app.
override fun onStart() {
        super.onStart()
        if (Util.SDK_INT > 23) {
            initializePlayer()
        }
    }

    override fun onResume() {
        super.onResume()
        if (Util.SDK_INT <= 23 || mPlayer == null) {
            initializePlayer()
        }
    }

Ha ha, may be.
That's it mark nothing else. 
And before leaving just wanted to check, is there any new books that is pipeline ?

Okay, Elements of jetpack compose is something to look for, always had a trouble with online blogs.

On a side note, if I can ask you some suggestions of how do I improve android skills on daily basis, as I feel I am left out just doing my office works which is sometimes mundane

That's it mark. Thanks. 
Have a good day.