NetworkStatusTracker_full.kt

import android.content.Context
import android.net.ConnectivityManager
import android.net.Network
import android.net.NetworkCapabilities
import android.net.NetworkRequest
import android.os.Bundle
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.FlowPreview
import kotlinx.coroutines.channels.awaitClose
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.callbackFlow
import kotlinx.coroutines.flow.distinctUntilChanged
import kotlinx.coroutines.flow.flatMapConcat
import kotlinx.coroutines.flow.map

class MainActivity : AppCompatActivity() {

    private val viewModel: NetworkStatusViewModel by lazy {
        ViewModelProvider(
            this,
            object : ViewModelProvider.Factory {
                override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                    val networkStatusTracker = NetworkStatusTracker(this@MainActivity)
                    return NetworkStatusViewModel(networkStatusTracker) as T
                }
            },
        ).get(NetworkStatusViewModel::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        viewModel.state.observe(this) { state ->
            findViewById<TextView>(R.id.textView).text = when (state) {
                MyState.Fetched -> "Fetched"
                MyState.Error -> "Error"
            }
        }
    }
}

sealed class MyState {
    object Fetched : MyState()
    object Error : MyState()
}

class NetworkStatusViewModel(
    networkStatusTracker: NetworkStatusTracker,
) : ViewModel() {

    val state =
        networkStatusTracker.networkStatus
            .map(
                onAvailable = { MyState.Fetched },
                onUnavailable = { MyState.Error },
            )
            .asLiveData(Dispatchers.IO)
}

sealed class NetworkStatus {
    object Available : NetworkStatus()
    object Unavailable : NetworkStatus()
}

class NetworkStatusTracker(context: Context) {

    private val connectivityManager =
        context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

    val networkStatus = callbackFlow<NetworkStatus> {
        val networkStatusCallback = object : ConnectivityManager.NetworkCallback() {
            override fun onUnavailable() {
                println("onUnavailable")
                offer(NetworkStatus.Unavailable)
            }

            override fun onAvailable(network: Network) {
                println("onAvailable")
                offer(NetworkStatus.Available)
            }

            override fun onLost(network: Network) {
                println("onLost")
                offer(NetworkStatus.Unavailable)
            }
        }

        val request = NetworkRequest.Builder()
            .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
            .build()
        connectivityManager.registerNetworkCallback(request, networkStatusCallback)

        awaitClose {
            connectivityManager.unregisterNetworkCallback(networkStatusCallback)
        }
    }
        .distinctUntilChanged()
}

@FlowPreview
inline fun <Result> Flow<NetworkStatus>.map(
    crossinline onUnavailable: suspend () -> Result,
    crossinline onAvailable: suspend () -> Result,
): Flow<Result> = map { status ->
    when (status) {
        NetworkStatus.Unavailable -> onUnavailable()
        NetworkStatus.Available -> onAvailable()
    }
}

@FlowPreview
inline fun <Result> Flow<NetworkStatus>.flatMap(
    crossinline onUnavailable: suspend () -> Flow<Result>,
    crossinline onAvailable: suspend () -> Flow<Result>,
): Flow<Result> = flatMapConcat { status ->
    when (status) {
        NetworkStatus.Unavailable -> onUnavailable()
        NetworkStatus.Available -> onAvailable()
    }
}

Great gist and great article! I'm just curious, why not use normal enum classes if all sealed class subclasses are just objects?

Thank you very much, am glade you like it.
I prefer sealed class over enum class. That's it. I use enum class regularly just chose sealed class here. In this case either one is valid.

This is super helpful — thank you for generously taking the time to share such an important example!

And one tiny request: if you could add the imports at the top of the file, it would help clarify where everything comes from.

Am glad you find this helpful! Thank you for kind words. I will add imports, thanks for suggestion.

The first time you enter it is not called to know the status of the connection, it is only called when it changes. Only happens when you dont have connection. Google issue? https://issuetracker.google.com/issues/144891976

excellent code

@thotluna thank you very much. am really glad you like it!

@PatricioIN I didn't encounter any issues. I will retest it and update gist if I encounter any errors

If your requirement is "NOTIFY only if no network connection exists neither Wifi nor Mobile Internet or one of them exists" then this modification can be helpful --> NetworkCheck

The first time you enter it is not called to know the status of the connection, it is only called when it changes. Only happens when you dont have connection. Google issue?

The same issue as @PatricioIN
It doesn't trigger for the first time. Although, I use this collectIn directly to collect the emission:

inline fun <T> Flow<T>.collectIn(
    owner: LifecycleOwner,
    minActiveState: Lifecycle.State = Lifecycle.State.STARTED,
    coroutineContext: CoroutineContext = EmptyCoroutineContext,
    crossinline action: suspend (T) -> Unit,
) = owner.lifecycleScope.launch(coroutineContext) {
    owner.lifecycle.repeatOnLifecycle(minActiveState) {
        collect {
            action(it)
        }
    }
}

but when I change the wifi/data, it works!

---

Update:
I followed what you did and still, it doesn't work when the internet is already disconnected.

---

Update:
I had to add connectivityManager.requestNetwork(request, networkStatusCallback, 1000) too, now it works 🎉

I'm just starting to tinker with this (and Compose). With latest studio and up-to-date implementations I have a error I don't know how to fix.
In the construction of the ViewModel via the Factory, I received an error pinned on the "object" line which reads:
Inheritance from an interface with '@JvmDefault' members is only allowed with -Xjvm-default option
Have you seen this and do you have any suggestions on what I should do to fix it?
thanks,
steve

@sralpert Better to ask that on Stackoverflow but maybe this helps: https://stackoverflow.com/questions/70992947/how-do-i-resolve-error-message-inheritance-from-an-interface-with-jvmdefault

@sralpert I will check it out

@sralpert sorry for late response. I can't reproduce that, no issues when I try to implement it. best is to follow that StackOverflow link

I'll try to implement it again in a small project. If it recurs, I'll try to email to you. /steve

…

On 11/8/2022 5:17 AM, Marko Novakovic wrote: Re: marenovakovic/NetworkStatusTracker_full.kt ***@***.**** commented on this gist. -------------------------------------------------------------------------------- @sralpert <https://github.com/sralpert> sorry for late response. I can't reproduce that, no issues when I try to implement it. best is to follow that StackOverflow link — Reply to this email directly, view it on GitHub <https://gist.github.com/9466bfc1b765e06e1b3600efbc4da2f8#gistcomment-4362166> or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABNZPETSS44647C3HJLZYWTWHISDLBFKMF2HI4TJMJ2XIZLTSKBKK5TBNR2WLJDHNFZXJJDOMFWWLK3UNBZGKYLEL52HS4DFQKSXMYLMOVS2I5DSOVS2I3TBNVS3W5DIOJSWCZC7OBQXE5DJMNUXAYLOORPWCY3UNF3GS5DZVRZXKYTKMVRXIX3UPFYGLK2HNFZXIQ3PNVWWK3TUUZ2G64DJMNZZDAVEOR4XAZNEM5UXG5FFOZQWY5LFVEYTAOBXGM4DGNBUU52HE2LHM5SXFJTDOJSWC5DF>. You are receiving this email because you were mentioned. Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

-- Steve Alpert ***@***.***

@Drjacky sorry. Where did you put the line connectivityManager.requestNetwork(request, networkStatusCallback, 1000)? Thank you very much

@PatricioIN

...
    val request = NetworkRequest.Builder()
            .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
            .build()

        connectivityManager.registerNetworkCallback(request, callback)
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            connectivityManager.requestNetwork(request, callback, 1000) //THISSSS
        }

        awaitClose {
            connectivityManager.unregisterNetworkCallback(callback)
        }
    }
        .distinctUntilChanged()