Android Build with Gradle and ProGuard : "The output jar must be specified after an input jar, or it will be empty"

Question

I'm creating a build with different flavors with Gradle. It used to run quite good until now, until I wanted to enable Proguard. I enabled minifyEnabled for my Release Build and now I'm having an exception saying :

"Caused by: org.gradle.internal.UncheckedException: java.io.IOException: The output jar [.../app/build/intermediates/multi-dex/dev/release/componentClasses.jar] must be specified after an input jar, or it will be empty."

Does anybody know what is causing this exception ? I basically want to enable ProGuard before I release my application. Here is my Gradle file below.

lintOptions {
    abortOnError false
}

dexOptions{
    incremental true
    javaMaxHeapSize "4g"
}

defaultConfig {
        applicationId "..."
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
    }

buildTypes {

    release {
        minifyEnabled true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        signingConfig signingConfigs.release
    }

    debug {
        minifyEnabled false
        shrinkResources false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        signingConfig signingConfigs.debug
    }
}

ProGuard Rules file.

# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in /Users/osayilgan/Development/Android/sdk/tools/proguard/proguard-android.txt
# You can edit the include path and order by changing the proguardFiles
# directive in build.gradle.
#
# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

# Add any project specific keep options here:

# If your project uses WebView with JS, uncomment the following
# and specify the fully qualified class name to the JavaScript interface
# class:
#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
#   public *;
#}

-keepnames public class * extends io.realm.RealmObject
-keep class io.realm.** { *; }
-dontwarn javax.**
-dontwarn io.realm.**

And Here is the proguard-android file. This is the default one from Android SDK.

# This is a configuration file for ProGuard.
# http://proguard.sourceforge.net/index.html#manual/usage.html

-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-verbose

# Optimization is turned off by default. Dex does not like code run
# through the ProGuard optimize and preverify steps (and performs some
# of these optimizations on its own).
-dontoptimize
-dontpreverify
# Note that if you want to enable optimization, you cannot just
# include optimization flags in your own project configuration file;
# instead you will need to point to the
# "proguard-android-optimize.txt" file instead of this one from your
# project.properties file.

-keepattributes *Annotation*
-keep public class com.google.vending.licensing.ILicensingService
-keep public class com.android.vending.licensing.ILicensingService

# For native methods, see http://proguard.sourceforge.net/manual/examples.html#native
-keepclasseswithmembernames class * {
    native <methods>;
}

# keep setters in Views so that animations can still work.
# see http://proguard.sourceforge.net/manual/examples.html#beans
-keepclassmembers public class * extends android.view.View {
   void set*(***);
   *** get*();
}

# We want to keep methods in Activity that could be used in the XML attribute onClick
-keepclassmembers class * extends android.app.Activity {
   public void *(android.view.View);
}

# For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

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

-keepclassmembers class **.R$* {
    public static <fields>;
}

# The support library contains references to newer platform versions.
# Don't warn about those in case this app is linking against an older
# platform version.  We know about them, and they are safe.
-dontwarn android.support.**

can you provide your proguard file? – Vic Vuci Jun 03 '15 at 21:39 — Vic Vuci, Jun 03 '15 at 21:39
@VicVu I updated my question with ProGuard files. – osayilgan Jun 03 '15 at 21:45 — osayilgan, Jun 03 '15 at 21:45

score 22 · Accepted Answer · edited Oct 21 '15 at 07:58

22

It took quite a while for me to figure it out but, as I had guessed, it was all about Proguard configuration.

I started to dig through the Warnings in the Console and realized that some of the References couldn't be found by Proguard. So adding them as -dontwarn to proguard configuration file solved the problem.

In my case, I had to ignore packages below;

-dontwarn java.lang.invoke**
-dontwarn org.apache.lang.**
-dontwarn org.apache.commons.**
-dontwarn com.nhaarman.**
-dontwarn se.emilsjolander.**

edited Oct 21 '15 at 07:58

JonasVautherin

7,297
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answered Jun 04 '15 at 02:10

osayilgan

5,873
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hi @osayilgan i am facing the same issue . and it doesnt work for me i put this in my progurad rules pro file . should i put any where else – shivpal jodha Jul 14 '16 at 12:37
@shivpaljodha These proguard rules are just an example. You need to find out which dependencies make trouble for you. Pay attention to the Warnings and Errors in the LogCat so you can figure out. – osayilgan Jul 14 '16 at 18:56

Android Build with Gradle and ProGuard : "The output jar must be specified after an input jar, or it will be empty"

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