Firebase Remote Config : NullPointerException on Map.keySet()

Question

I am getting the following crash for a lot of users :

Fatal Exception: java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Set java.util.Map.keySet()' on a null object reference
   at com.google.android.gms.internal.zzbtn.zza(Unknown Source)
   at com.google.android.gms.internal.zzbtn.run(Unknown Source)
   at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
   at java.lang.Thread.run(Thread.java:818)

I searched through external libraries and found that the source of crash is firebase-config library in the following class zzbtn(see method - zza()).

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.google.android.gms.internal;

import android.content.Context;
import android.util.Log;
import com.google.android.gms.internal.zzbtl;
import com.google.android.gms.internal.zzbto;
import com.google.android.gms.internal.zzbtr;
import com.google.android.gms.internal.zzbxt;
import com.google.android.gms.internal.zzbts.zza;
import com.google.android.gms.internal.zzbts.zzb;
import com.google.android.gms.internal.zzbts.zzc;
import com.google.android.gms.internal.zzbts.zzd;
import com.google.android.gms.internal.zzbts.zze;
import com.google.android.gms.internal.zzbts.zzf;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class zzbtn implements Runnable {
public final Context mContext;
public final zzbto zzclY;
public final zzbto zzclZ;
public final zzbto zzcma;
public final zzbtr zzclQ;

    public zzbtn(Context var1, zzbto var2, zzbto var3, zzbto var4, zzbtr var5) {
        this.mContext = var1;
        this.zzclY = var2;
        this.zzclZ = var3;
        this.zzcma = var4;
        this.zzclQ = var5;
    }

    private zza zza(zzbto var1) {
        zza var2 = new zza();
        if(var1.zzace() != null) {
            Map var3 = var1.zzace();
            ArrayList var4 = new ArrayList();
            Iterator var5 = var3.keySet().iterator();

            while(var5.hasNext()) {
                String var6 = (String)var5.next();
                ArrayList var7 = new ArrayList();
                Map var8 = (Map)var3.get(var6);
                /* Crash is here when reading keySet() on null map */
                Iterator var9 = var8.keySet().iterator();

                while(var9.hasNext()) {
                    String var10 = (String)var9.next();
                    zzb var11 = new zzb();
                    var11.zzaB = var10;
                    var11.zzcml = (byte[])var8.get(var10);
                    var7.add(var11);
                }

                zzd var16 = new zzd();
                var16.zzaGP = var6;
                zzb[] var12 = new zzb[var7.size()];
                var16.zzcmq = (zzb[])var7.toArray(var12);
                var4.add(var16);
            }

            zzd[] var15 = new zzd[var4.size()];
            var2.zzcmi = (zzd[])var4.toArray(var15);
        }

        if(var1.zzzD() != null) {
            List var13 = var1.zzzD();
            byte[][] var14 = new byte[var13.size()][];
            var2.zzcmj = (byte[][])var13.toArray(var14);
        }

        var2.timestamp = var1.getTimestamp();
        return var2;
    }

    public void run() {
        zze var1 = new zze();
        if(this.zzclY != null) {
            var1.zzcmr = this.zza(this.zzclY);
        }

        if(this.zzclZ != null) {
            var1.zzcms = this.zza(this.zzclZ);
        }

        if(this.zzcma != null) {
            var1.zzcmt = this.zza(this.zzcma);
        }

        if(this.zzclQ != null) {
            zzc var2 = new zzc();
            var2.zzcmm = this.zzclQ.getLastFetchStatus();
            var2.zzcmn = this.zzclQ.isDeveloperModeEnabled();
            var2.zzcmo = this.zzclQ.zzacj();
            var1.zzcmu = var2;
        }

        if(this.zzclQ != null && this.zzclQ.zzach() != null) {
            ArrayList var8 = new ArrayList();
            Map var3 = this.zzclQ.zzach();
            Iterator var4 = var3.keySet().iterator();

            while(var4.hasNext()) {
                String var5 = (String)var4.next();
                if(var3.get(var5) != null) {
                    zzf var6 = new zzf();
                    var6.zzaGP = var5;
                    var6.zzcmx = ((zzbtl)var3.get(var5)).zzacd();
                    var6.resourceId = ((zzbtl)var3.get(var5)).zzacc();
                    var8.add(var6);
                }
            }

            zzf[] var11 = new zzf[var8.size()];
            var1.zzcmv = (zzf[])var8.toArray(var11);
        }

        byte[] var9 = zzbxt.zzf(var1);

        try {
            FileOutputStream var10 = this.mContext.openFileOutput("persisted_config", 0);
            var10.write(var9);
            var10.close();
        } catch (IOException var7) {
            Log.e("AsyncPersisterTask", "Could not persist config.", var7);
        }

    }
}

This class is used in FirebaseRemoteConfig class (see method zzt()) as given below :

https://gist.github.com/anonymous/e6f23c1dc37bf905a9224d8b72ab6cd9

And I am using FirebaseRemoteConfig in my application class as below :

public class MyApp extends MultiDexApplication {

    public static boolean sound = true;
    private static Context context;

    private Typeface regularTypeFace;
    private Typeface boldTypeFace;
    private final String LOG_TAG = "MyApp";
    private FirebaseRemoteConfig remoteConfig = null;

    @Override
    public void onCreate() {
        super.onCreate();

        Fabric.with(this, new Crashlytics());

        context = getApplicationContext();

        /* Try catch to handle any runtime exception thrown by firebase API */
        try {
            /* Initialize firebase app : Done to avoid crashes due to IllegalStateException - Default FirebaseApp is not initialized */
            FirebaseApp.initializeApp(this);
            /* Start to fetch Remote config parameters */
            startConfigFetch();
        } catch (Exception e){
            e.printStackTrace();
        }

    }

    /**
     * Description : Fetches remote config params from firebase & uses the fetched values
     */
    public void startConfigFetch() {

        /* try to get the default instance of Firebase Remote config */
        /* try-catch : To Resolve Crash #1399 */
        try {
            remoteConfig = FirebaseRemoteConfig.getInstance();
        } catch (IllegalStateException e){
            e.printStackTrace();
        }

        /* If we don't get an instance of Firebase remote config, then do nothing */
        if (remoteConfig == null){
            return;
        }

        FirebaseRemoteConfigSettings remoteConfigSettings = new FirebaseRemoteConfigSettings.Builder()
                .setDeveloperModeEnabled(BuildConfig.DEBUG)
                .build();

        remoteConfig.setConfigSettings(remoteConfigSettings);
        remoteConfig.setDefaults(R.xml.remote_config_defaults);

        /* Time for which cache lives, for now its 0 ms */
        long cacheExpiration = 0;

        OnCompleteListener<Void> onCompleteListener = new OnCompleteListener<Void>() {
            @Override
            public void onComplete(@NonNull Task<Void> task) {

                if (task.isSuccessful()) {
                    if (getContext() != null) {
                        onFetchConfigSuccess();
                    }
                } else {
                    Log.d(LOG_TAG, "Stories Fetch Fail");
                }
            }
        };

        OnFailureListener onFailListener = new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Log.d(LOG_TAG, "Stories Fetch Fail in remote config");
            }
        };

        remoteConfig.fetch(cacheExpiration).addOnCompleteListener(onCompleteListener).addOnFailureListener(onFailListener);
    }

    /**
     * Called when fetch config is success
     * */
    private void onFetchConfigSuccess() {

        /* Once the config is successfully fetched it must be activated before newly fetched */
        /* values are returned (or can be used) */
        remoteConfig.activateFetched();

        /* Get dynamic stories string */
        String dynamicStories = remoteConfig.getString(Common.KEY_DYNAMIC_STORIES_FIREBASE_CONFIG);
        /* Get bundled stories (these are app-bundled stories & dynamic stories but part of bundled stories) */
        String bundledStories = remoteConfig.getString(Common.KEY_BUNDLED_STORIES_FIREBASE_CONFIG);

    /* Do something with dynamicStories & bundledStories values */
    }

}

And class zzbto is here :

https://gist.github.com/anonymous/e2f3a67e6fd3be51ba4456fe2e847890

Please help to resolve this crash.

Answer 1

As stated in Kirril Karmizin's comment, it's a known bug since June 2017 (Github Firebase issues). I also received multiple crash reports

Fatal Exception: java.lang.NullPointerException
   at com.google.android.gms.internal.zzdyx.zzb(Unknown Source)
   at com.google.android.gms.internal.zzdyx.zza(Unknown Source)
   at com.google.android.gms.internal.zzfan.run(Unknown Source)
   at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
   at java.lang.Thread.run(Thread.java:848)

, with:

• Firebase: 12.0.1
• buildTools: 27.0.3

A probable step in the right direction for those that would want to keep Remote Config in their apps can be found in Official RemoteConfic docs:

You should set in-app default parameter values in the Remote Config object, so that your app behaves predictably before it fetches values from the Remote Config service.

For me, I could not risk more crash reports in a production app. I removed Remote Config and I've seen no crashes until now.

Answer 2

The bug @Ευάγγελος pointed out was fixed in version 15.0.0. However, that version introduced another bug that was also causing NullPointerException. Fortunately, it was quickly fixed in 15.0.2.