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@marenovakovic
Last active July 18, 2024 08:18
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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()
}
}
@marenovakovic
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Author

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

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

@gsrathoreniks
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gsrathoreniks commented Jun 24, 2022

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

@Drjacky
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Drjacky commented Aug 26, 2022

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 🎉

@sralpert
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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

@Drjacky
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Drjacky commented Oct 21, 2022

@marenovakovic
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@sralpert I will check it out

@marenovakovic
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@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

@sralpert
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sralpert commented Nov 8, 2022 via email

@PatricioIN
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PatricioIN commented Nov 8, 2022

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

@Drjacky
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Drjacky commented Nov 9, 2022

@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()

@hafiz013
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Can have checking connection in kotlin multiplatform instead of seperate android and ios?

@marenovakovic
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marenovakovic commented Jul 18, 2024

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