blog-connectivitylivedata-class.kt

import android.app.Application
import android.arch.lifecycle.LiveData
import android.content.Context
import android.net.ConnectivityManager
import android.net.Network
import android.net.NetworkInfo
import android.net.NetworkRequest
import android.os.Build
import android.support.annotation.RequiresPermission
import android.support.annotation.VisibleForTesting

/**
 * A LiveData class which wraps the network connection status
 * Requires Permission: ACCESS_NETWORK_STATE
 *
 * See https://developer.android.com/training/monitoring-device-state/connectivity-monitoring
 * See https://developer.android.com/reference/android/net/ConnectivityManager
 * See https://developer.android.com/reference/android/net/ConnectivityManager#CONNECTIVITY_ACTION
 */
class ConnectivityLiveData @VisibleForTesting internal constructor(private val connectivityManager: ConnectivityManager)
    : LiveData<Boolean>() {

    @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
    constructor(application: Application) : this(application.getSystemService(Context.CONNECTIVITY_SERVICE)
        as ConnectivityManager)

    private val networkCallback = object : ConnectivityManager.NetworkCallback() {
        override fun onAvailable(network: Network?) {
            postValue(true)
        }

        override fun onLost(network: Network?) {
            postValue(false)
        }
    }

    override fun onActive() {
        super.onActive()

        val activeNetwork: NetworkInfo? = connectivityManager.activeNetworkInfo
        postValue(activeNetwork?.isConnectedOrConnecting == true)

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            connectivityManager.registerDefaultNetworkCallback(networkCallback)
        } else {
            val builder = NetworkRequest.Builder()
            connectivityManager.registerNetworkCallback(builder.build(), networkCallback)
        }
    }

    override fun onInactive() {
        super.onInactive()
        connectivityManager.unregisterNetworkCallback(networkCallback)
    }
}

How to use this in viewmodel

    val getConnectivity: ConnectivityLiveData by lazy {
       ...??
    }

You can create one by using the constructor which takes an Application. Ensure your ViewModel is an AndroidViewModel then you'll have access to an Application.

Something a bit like this would work:

internal class MyViewModel(
    application: Application
    private val connectivity: LiveData<Boolean>
) : AndroidViewModel(application) {

    constructor(application: Application) : this(
        application = application,
        connectivity = ConnectivityLiveData(application)
    )

    // ...

}

Or if you want to use lazy it should be something like:

val getConnectivity: ConnectivityLiveData by lazy {
    ConnectivityLiveData(getApplication<Application>())
}

FYI, this is the accompanying blog post https://android.jlelse.eu/connectivitylivedata-6861b9591bcc

Ley me know if this doesn't work for you.

Hey, Thanks,
I modified your solution a little, by detecting network to check if there is an internet connection, using ping

class ConnectivityLiveData internal constructor(private val connectivityManager: ConnectivityManager) :
    LiveData<Boolean>() {

    @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
    constructor(application: Application) : this(
        application.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
    )

    private val networkCallback = object : ConnectivityManager.NetworkCallback() {
        override fun onAvailable(network: Network?) {
            postValue(isInternetOn())
        }

        override fun onLost(network: Network?) {
            postValue(false)
        }

    }

    override fun onActive() {
        super.onActive()
        postValue(isInternetOn())

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            connectivityManager.registerDefaultNetworkCallback(networkCallback)
        } else {
            val builder = NetworkRequest.Builder()
                .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR)
                .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
            connectivityManager.registerNetworkCallback(builder.build(), networkCallback)
        }
    }

    override fun onInactive() {
        super.onInactive()
        connectivityManager.unregisterNetworkCallback(networkCallback)
    }

    fun isNetworkIsAvailable(): Boolean {
        val activeNetwork: NetworkInfo? = connectivityManager.activeNetworkInfo
        return activeNetwork?.isConnected == true
    }

    fun isInternetOn(): Boolean {
        if (isNetworkIsAvailable()) {
            try {
                val p = java.lang.Runtime.getRuntime().exec("ping -c 1 www.google.com")
                val value = p.waitFor()
                return value == 0

            } catch (e: Exception) {
                e.printStackTrace()
            }
        }
        return false
    }
}

Interesting approach. I have never seen something like this java.lang.Runtime.getRuntime().exec("ping -c 1 www.google.com") before. Is this thread safe?

Yes, at the moment what is found works in all versions of Android, the alternative is to use .isRecheable but it does not offer the same reliability
I see in. https://stackoverflow.com/questions/9922543/why-does-inetaddress-isreachable-return-false-when-i-can-ping-the-ip-address

Very interesting. Thank you for sharing.