ConnectivityManager.CONNECTIVITY_ACTION deprecated

What will be deprecated is the ability for a backgrounded application to receive network connection state changes.

As David Wasser said you can still get notified of connectivity changes if the app component is instantiated (not destroyed) and you have registered your receiver programmatically with its context, instead of doing it in the manifest.

Or you can use NetworkCallback instead. In particular, you will need to override onAvailable for connected state changes.

Let me draft a snippet quickly:

public class ConnectionStateMonitor extends NetworkCallback {

   final NetworkRequest networkRequest;

   public ConnectionStateMonitor() {
       networkRequest = new NetworkRequest.Builder()
           .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR)
           .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
           .build();
   }

   public void enable(Context context) {
       ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
       connectivityManager.registerNetworkCallback(networkRequest, this);
   }

   // Likewise, you can have a disable method that simply calls ConnectivityManager.unregisterNetworkCallback(NetworkCallback) too.

   @Override
   public void onAvailable(Network network) {
       // Do what you need to do here
   }
}

I will update Sayem's answer for fix lint issues its showing to me.

class ConnectionLiveData(val context: Context) : LiveData<Boolean>() {

    private var connectivityManager: ConnectivityManager = context.getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager

    private lateinit var connectivityManagerCallback: ConnectivityManager.NetworkCallback

    private val networkRequestBuilder: NetworkRequest.Builder = NetworkRequest.Builder()
        .addTransportType(android.net.NetworkCapabilities.TRANSPORT_CELLULAR)
        .addTransportType(android.net.NetworkCapabilities.TRANSPORT_WIFI)

    override fun onActive() {
        super.onActive()
        updateConnection()
        when {
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.N -> connectivityManager.registerDefaultNetworkCallback(getConnectivityMarshmallowManagerCallback())
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.M -> marshmallowNetworkAvailableRequest()
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP -> lollipopNetworkAvailableRequest()
            else -> {
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
                    context.registerReceiver(networkReceiver, IntentFilter("android.net.conn.CONNECTIVITY_CHANGE")) // android.net.ConnectivityManager.CONNECTIVITY_ACTION
                }
            }
        }
    }

    override fun onInactive() {
        super.onInactive()
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            connectivityManager.unregisterNetworkCallback(connectivityManagerCallback)
        } else {
            context.unregisterReceiver(networkReceiver)
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun lollipopNetworkAvailableRequest() {
        connectivityManager.registerNetworkCallback(networkRequestBuilder.build(), getConnectivityLollipopManagerCallback())
    }

    @TargetApi(Build.VERSION_CODES.M)
    private fun marshmallowNetworkAvailableRequest() {
    connectivityManager.registerNetworkCallback(networkRequestBuilder.build(), getConnectivityMarshmallowManagerCallback())
    }

    private fun getConnectivityLollipopManagerCallback(): ConnectivityManager.NetworkCallback {
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
           connectivityManagerCallback = object : ConnectivityManager.NetworkCallback() {
               override fun onAvailable(network: Network?) {
                   postValue(true)
               }

               override fun onLost(network: Network?) {
                   postValue(false)
               }
           }
           return connectivityManagerCallback
       } else {
           throw IllegalAccessError("Accessing wrong API version")
       }
    }

    private fun getConnectivityMarshmallowManagerCallback(): ConnectivityManager.NetworkCallback {
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
          connectivityManagerCallback = object : ConnectivityManager.NetworkCallback() {
            override fun onCapabilitiesChanged(network: Network?, networkCapabilities: NetworkCapabilities?) {
                networkCapabilities?.let { capabilities ->
                    if (capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) && capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED)) {
                        postValue(true)
                    }
                }
            }
            override fun onLost(network: Network?) {
                postValue(false)
            }
         }
         return connectivityManagerCallback
       } else {
         throw IllegalAccessError("Accessing wrong API version")
       }
    }

    private val networkReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            updateConnection()
        }
    }

    private fun updateConnection() {
        val activeNetwork: NetworkInfo? = connectivityManager.activeNetworkInfo
        postValue(activeNetwork?.isConnected == true)
    }
}

And same usage:

    val connectionLiveData = ConnectionLiveData(context)
    connectionLiveData.observe(this, Observer { isConnected ->
           isConnected?.let {
             // do job
           }
    })

Btw thanks sayem for your solution.