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I have an OkHttp client which uses my custom network interceptor in order to insert token into requests header.

I keep on getting the exception

E/AndroidRuntime: FATAL EXCEPTION: OkHttp Dispatcher 
   Process: com.edstart.tazuzu, PID: 32093
   java.lang.NullPointerException: interceptor com.edstart.tazuzu.RestAPI.RequestsErrorInterceptor@2bde70f returned null
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:157)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
       at com.edstart.tazuzu.RestAPI.TazuzuRequestsInterceptor.intercept(TazuzuRequestsInterceptor.kt:30)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
       at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
       at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
       at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
       at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:126)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
       at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:254)
       at okhttp3.RealCall$AsyncCall.execute(RealCall.java:200)
       at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
       at java.lang.Thread.run(Thread.java:764)
I have tried surrounding the interceptor with try/catch. and also throwing error in order to avoid app crash but with no good results.
The interceptor code:
package com.edstart.tazuzu.RestAPI
import android.util.Log
import com.edstart.tazuzu.Managers.ServerManager
import okhttp3.Interceptor
import okhttp3.Response
import java.net.InetAddress
import kotlin.Exception
 * interceptor for the tazuzu api requests to insert the token before the request
 * send to the server (for authentication)
class TazuzuRequestsInterceptor : Interceptor {
    override fun intercept(chain: Interceptor.Chain?): Response? {
        try {
            if (!isInternetAvailable()) {
                throw Exception()
            } else {
                var request = chain?.request()
                if (request != null) {
                    val builder = request.newBuilder()
                    if (builder != null) {
                        builder.addHeader("x-access-token", ServerManager.token)
                        request = builder.build()
                        if (request != null && chain != null) {
                            return chain.proceed(request)
        } catch (e: java.lang.Exception) {
            Log.e("###", e.toString())
            throw e
        return null
    private fun isInternetAvailable(): Boolean {
        return try {
            val ipAddr = InetAddress.getByName("google.com")
            //You can replace it with your name
            !ipAddr.equals("")
        } catch (e: Exception) {
            false
Please help, looking for ways controlling exceptions in a way it won't make the app crash.
                The stacktrace says it's RequestsErrorInterceptor and not TazuzuRequestsInterceptor you posted.
– laalto
                Jan 22, 2019 at 9:22
class ErrorHandlingInterceptor : Interceptor {
    override fun intercept(chain: Interceptor.Chain): Response {
        val request = chain.request()
        val response = chain.proceed(request)
        if (!isInternetAvailable()) {
            // Do your thing
            // 1. Either throw a generic exception
            // 2. Throw an exception with your own custom status code that can be checked on the callbacks
            // 3. Create an interface callback
            // example throw invocation
            throw Exception()
        } else {
            val builder = request.newBuilder()
            builder?.let { builder ->
                builder.addHeader("x-access-token", ServerManager.token)
            request = builder.build()
            // No need for this additional checks
            // if (request != null && chain != null) { ... }
            return chain.proceed(request)
private fun isInternetAvailable(): Boolean {
    return try {
        val ipAddr = InetAddress.getByName("google.com")
        //You can replace it with your name
        !ipAddr.equals("")
    } catch (e: Exception) {
        false
If for example, you have chosen to throw an exception when there's no internet connection, you could just handle everything in onFailure()callback of the retrofit call. 
Or if you are using rxjava, you can just subscribe for the error on the error callback handler.
Read more on
https://futurestud.io/tutorials/retrofit-2-catch-server-errors-globally-with-response-interceptor
https://medium.com/@tsaha.cse/advanced-retrofit2-part-1-network-error-handling-response-caching-77483cf68620
I had this error when tried to launch request in Main Thread. Try to use coroutines, just wrap your Retrofit-request call with CoroutineScope:
val apiService = RetrofitFactory.makeRetrofitService()
    CoroutineScope(Dispatchers.IO).launch {
        val response = apiService.myPostRequest()
        // process response...
        
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