Question

Currently, I’m having experience that, a piece of code, which makes use of Google Drive API is running fine without introducing ProGuard.

However, after introducing ProGuard, I’m getting the following run-time error.

    at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.NullPointerException
    at com.google.api.client.util.Types.getActualParameterAtPosition(Types.java:329)
    at com.google.api.client.util.Types.getIterableParameter(Types.java:309)
    at com.google.api.client.json.JsonParser.parseValue(JsonParser.java:546)
    at com.google.api.client.json.JsonParser.parse(JsonParser.java:350)
    at com.google.api.client.json.JsonParser.parseValue(JsonParser.java:586)
    at com.google.api.client.json.JsonParser.parse(JsonParser.java:289)
    at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:76)
    at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:71)
    at com.google.api.client.http.HttpResponse.parseAs(HttpResponse.java:491)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:456)
    at com.jstock.c.b.a(CloudFile.java:136)

Note, the crash happens at my code (which is com.jstock.c.b.a if I retrace using mapping.txt)

// request is Files.List
FileList files = request.execute();

In my proguard, I thought having the following 2 key instructions, able to prevent the crash from happen : I tell ProGuard never touch on jackson and Google libraries.

-keep class org.codehaus.** { *; }
-keep class com.google.** { *; }
-keep interface org.codehaus.** { *; }
-keep interface com.google.** { *; }

But that doesn’t work. NPE still happen at Types.java

Note that, I had another try is that, I thought obfuscate process causes NPE happens. Hence, I try to disable it using -dontobfuscate. But this time, I will not able to generate APK file, and getting a popular error message : Conversion to Dalvik format failed with error 1

Here is the proguard configuration which causes NPE at Google Drive API.

-optimizationpasses 1
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontpreverify
-verbose
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*

# Comment out the following line, will cause popular "Conversion to Dalvik format failed with error 1"
##-dontobfuscate

-dontwarn sun.misc.Unsafe
-dontwarn com.google.common.collect.MinMaxPriorityQueue
-dontwarn javax.swing.**
-dontwarn java.awt.**
-dontwarn org.jasypt.encryption.pbe.**
-dontwarn java.beans.**
-dontwarn org.joda.time.**
-dontwarn com.google.android.gms.**
-dontwarn org.w3c.dom.bootstrap.**
-dontwarn com.ibm.icu.text.**
-dontwarn demo.**

# Hold onto the mapping.text file, it can be used to unobfuscate stack traces in the developer console using the retrace tool
-printmapping mapping.txt

# Keep line numbers so they appear in the stack trace of the develeper console 
-keepattributes *Annotation*,EnclosingMethod,SourceFile,LineNumberTable

-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference
-keep public class com.android.vending.licensing.ILicensingService

-keep class android.support.v4.app.** { *; }
-keep interface android.support.v4.app.** { *; }
-keep class com.actionbarsherlock.** { *; }
-keep interface com.actionbarsherlock.** { *; }

# https://sourceforge.net/p/proguard/discussion/182456/thread/e4d73acf
-keep class org.codehaus.** { *; }
-keep class com.google.** { *; }
-keep interface org.codehaus.** { *; }
-keep interface com.google.** { *; }

-assumenosideeffects class android.util.Log {
  public static int d(...);
  public static int i(...);
  public static int e(...);
  public static int v(...);  
}

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers class * extends android.app.Activity {
   public void *(android.view.View);
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

-assumenosideeffects class android.util.Log {
    public static *** d(...);
    public static *** v(...);
    public static *** i(...);
}

-keepclasseswithmembers class com.google.common.base.internal.Finalizer{
    <methods>;
}

Is there anything else I can try?

I’m not sure it might be caused by the combination of the libraries. (Although things run pretty well without introducing ProGuard)

If I look at the NPE crash location (Types.getActualParameterAtPosition(Types.java:329))

private static Type getActualParameterAtPosition(Type type, Class<?> superClass, int position) {
    ParameterizedType parameterizedType = Types.getSuperParameterizedType(type, superClass);
    Type valueType = parameterizedType.getActualTypeArguments()[position];
    // this is normally a type variable, except in the case where the class of iterableType is
    // superClass, e.g. Iterable<String>
    if (valueType instanceof TypeVariable<?>) {
      Type resolve = Types.resolveTypeVariable(Arrays.asList(type), (TypeVariable<?>) valueType);
      if (resolve != null) {
        return resolve;
      }
    }
    return valueType;
}

I suspect Types.getSuperParameterizedType returning null. So, I further look into Types.getSuperParameterizedType.

public static ParameterizedType getSuperParameterizedType(Type type, Class<?> superClass) {
    if (type instanceof Class<?> || type instanceof ParameterizedType) {
    outer: while (type != null && type != Object.class) {
     Class<?> rawType;
     if (type instanceof Class<?>) {
       // type is a class
       rawType = (Class<?>) type;
     } else {
       // current is a parameterized type
       ParameterizedType parameterizedType = (ParameterizedType) type;
       rawType = getRawClass(parameterizedType);
       // check if found Collection
       if (rawType == superClass) {
         // return the actual collection parameter
         return parameterizedType;
       }
       if (superClass.isInterface()) {
         for (Type interfaceType : rawType.getGenericInterfaces()) {
           // interface type is class or parameterized type
           Class<?> interfaceClass =
               interfaceType instanceof Class<?> ? (Class<?>) interfaceType : getRawClass(
                   (ParameterizedType) interfaceType);
           if (superClass.isAssignableFrom(interfaceClass)) {
             type = interfaceType;
             continue outer;
           }
         }
       }
     }
     // move on to the super class
     type = rawType.getGenericSuperclass();
    }
    }
    return null;
}

What is the possible root cause that may cause getSuperParameterizedType returning null, after processed by ProGuard?

Answer 1

A combination of the following has worked for me:

-keep class com.google.** { *;}
-keep interface com.google.** { *;}
-dontwarn com.google.**

-dontwarn sun.misc.Unsafe
-dontwarn com.google.common.collect.MinMaxPriorityQueue
-keepattributes *Annotation*,Signature
-keep class * extends com.google.api.client.json.GenericJson {
*;
}
-keep class com.google.api.services.drive.** {
*;
}

This provided a working proguard compatible solution for a recent Google Drive project.

Cannot take all credit for this solution though, originally found at this link here