How should I handle “No internet connection” with Retrofit on Android

Question

I\'d like to handle situations when there is no internet connection. Usually I\'d run:

ConnectivityManager cm =
    (ConnectivityManager)context.getSystemSer         


        

Answer 1

Here's what I did on API 29 & API 30:

1. I created a simple WiFiService class that will hold the connectivityManager:

   class WifiService {
    private lateinit var wifiManager: WifiManager
    private lateinit var connectivityManager: ConnectivityManager

    companion object {
        val instance = WifiService()
    }

    fun initializeWithApplicationContext (context: Context) {
        wifiManager = context.getSystemService(Context.WIFI_SERVICE) as WifiManager
        connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
    }

    // Helper that detects if online
    fun isOnline(): Boolean {
        val capabilities = connectivityManager.getNetworkCapabilities(connectivityManager.activeNetwork)
        if (capabilities != null) {
            when {
                capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> return true
                capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> return true
                capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> return true
            }
        }
        return false
      }
   }

2. Create the ConnectivityInterceptor to check for internet access:

   class ConnectivityInterceptor: Interceptor {
    override fun intercept(chain: Interceptor.Chain): Response {
        if (!WifiService.instance.isOnline()) {
            throw IOException("No internet connection")
        } else {
            return chain.proceed(chain.request())
        }
     }
   }

3. Finally use it in Retrofit2 as follows:

   class RestApi {
    private val okHttpClient by lazy {
        OkHttpClient.Builder()
            .addInterceptor(ConnectivityInterceptor())
            .build()
    }

    // Define all the retrofit clients
    private val restApiClient by lazy {
        Retrofit.Builder()
            .baseUrl("http://localhost:10000")
            .client(okHttpClient)
            .addConverterFactory(GsonConverterFactory.create())
            .build()
     }

     // ...
   }