How should I handle "No internet connection" with Retrofit on Android

Question

What I ended up doing is creating a custom Retrofit client that checks for connectivity before executing a request and throws an exception.

public class ConnectivityAwareUrlClient implements Client {

    Logger log = LoggerFactory.getLogger(ConnectivityAwareUrlClient.class);

    public ConnectivityAwareUrlClient(Client wrappedClient, NetworkConnectivityManager ncm) {
        this.wrappedClient = wrappedClient;
        this.ncm = ncm;
    }

    Client wrappedClient;
    private NetworkConnectivityManager ncm;

    @Override
    public Response execute(Request request) throws IOException {
        if (!ncm.isConnected()) {
            log.debug("No connectivity %s ", request);
            throw new NoConnectivityException("No connectivity");
        }
        return wrappedClient.execute(request);
    }
}

and then use it when configuring RestAdapter

RestAdapter.Builder().setEndpoint(serverHost)
                     .setClient(new ConnectivityAwareUrlClient(new OkHttpClient(), ...))

Since retrofit 1.8.0 this has been deprecated

retrofitError.isNetworkError()

you have to use

if (retrofitError.getKind() == RetrofitError.Kind.NETWORK)
{

}

there are multiple types of errors you can handle:

NETWORK An IOException occurred while communicating to the server, e.g. Timeout, No connection, etc...

CONVERSION An exception was thrown while (de)serializing a body.

HTTP A non-200 HTTP status code was received from the server e.g. 502, 503, etc...

UNEXPECTED An internal error occurred while attempting to execute a request. It is best practice to re-throw this exception so your application crashes.

With Retrofit 2, we use an OkHttp Interceptor implementation to check for network connectivity ahead of sending the request. If no network, throw an exception as appropriate.

This allows one to specifically handle network connectivity issues before hitting Retrofit.

import java.io.IOException;

import okhttp3.Interceptor;
import okhttp3.Response;
import io.reactivex.Observable

public class ConnectivityInterceptor implements Interceptor {

    private boolean isNetworkActive;

    public ConnectivityInterceptor(Observable<Boolean> isNetworkActive) {
       isNetworkActive.subscribe(
               _isNetworkActive -> this.isNetworkActive = _isNetworkActive,
               _error -> Log.e("NetworkActive error " + _error.getMessage()));
    }

    @Override
    public Response intercept(Interceptor.Chain chain) throws IOException {
        if (!isNetworkActive) {
            throw new NoConnectivityException();
        }
        else {
            Response response = chain.proceed(chain.request());
            return response;
        }
    }
}

public class NoConnectivityException extends IOException {

    @Override
    public String getMessage() {
        return "No network available, please check your WiFi or Data connection";
    }
}

@AlexV are you sure that the RetrofitError contains a timeout as a reason (SocketTimeOutException when getCause() is called) when there is no internet connection?

As far as I know when there is no internet connection the RetrofitError contains a ConnectionException as cause.

If you implement an ErrorHandler you can do something like this:

public class RetrofitErrorHandler implements ErrorHandler {

    @Override
    public Throwable handleError(RetrofitError cause) {
        if (cause.isNetworkError()) {
            if (cause.getCause() instanceof SocketTimeoutException) {
                return new MyConnectionTimeoutException();
            } else {
                return new MyNoConnectionException();
            }
        } else {
            [... do whatever you want if it's not a network error ...]  
        }
    }

}

just do this you will notified even for issues like

UnknownHostException

,

SocketTimeoutException

and others.

 @Override public void onFailure(Call<List<BrokenGitHubRepo>> call, Throwable t) {  
if (t instanceof IOException) {
    Toast.makeText(ErrorHandlingActivity.this, "this is an actual network failure :( inform the user and possibly retry", Toast.LENGTH_SHORT).show();
    // logging probably not necessary
}
else {
    Toast.makeText(ErrorHandlingActivity.this, "conversion issue! big problems :(", Toast.LENGTH_SHORT).show();
    // todo log to some central bug tracking service
} }

For Retrofit 1

When you get a Throwable error from your http request, you can detect whether it is a network error with a method like this:

String getErrorMessage(Throwable e) {
    RetrofitError retrofitError;
    if (e instanceof RetrofitError) {
        retrofitError = ((RetrofitError) e);
        if (retrofitError.getKind() == RetrofitError.Kind.NETWORK) {
            return "Network is down!";
        }
    }
}