I'm trying to use Proguard in my Xamarin.Android project, yet the compilation fails with the error Unsupported class version number [52.0] (maximum 51.0, Java 1.7)

I saw from those two questions that it may be a mismatch between Java 7 and Java 8, more precisely some versions of proguard don't support Java 8. However in Xamarin Preferences -> SDK Location, Java SDK points to JDK 7 : /Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home

Is there any place where proguard can be configured more precisely ? Any other idea ?

Here's the failure log : Can't read [/Library/Frameworks/Xamarin.Android.framework/Versions/7.0.0-18/lib/xbuild-frameworks/MonoAndroid/v7.0/] (Can't process class [android/app/ActivityTracker.class] (Unsupported class version number [52.0] (maximum 51.0, Java 1.7))) at proguard.InputReader.readInput( at proguard.InputReader.readInput( at proguard.InputReader.readInput( at proguard.InputReader.execute( at proguard.ProGuard.readInput( at proguard.ProGuard.execute( at proguard.ProGuard.main( Caused by: Can't process class [android/app/ActivityTracker.class] (Unsupported class version number [52.0] (maximum 51.0, Java 1.7)) at at at at at at proguard.InputReader.readInput( ... 6 more Caused by: java.lang.UnsupportedOperationException: Unsupported class version number [52.0] (maximum 51.0, Java 1.7) at proguard.classfile.util.ClassUtil.checkVersionNumbers( at at proguard.classfile.ProgramClass.accept( at ... 11 more

9 Warning(s) 1 Error(s)

4 Answers 11

up vote 95 down vote accepted

You need to update the default Android SDK proguard.jar with the latest version of Proguard found here:

I would recommend that you install this on the side of the default version that Android ships in android-sdk\tools\proguard. Simply rename the existing folder to something else and add the new version of proguard.

This is listed in the Xamarin.Android 7.0 release notes:

In which the following bug was logged as well:

Which is coordinated with a Pull Request in the Xamarin.Android repository:

2 upvote
This works for me, for the details I replace the Android tools/proguard/lib folder by the lib folder inside the latest Proguard release from sourceforge (5.3.2 at this time). – Guillaume Perrot
7 upvote
If you replace the whole proguard directory, make sure to copy the config files from the old directory: proguard-android-optimize.txt, proguard-android.txt, proguard-project.txt. – rooby
The most fantastic thing is that it really helps even 2 years ago ) Thx man, you've saved my day. – Darkmike
1 upvote
Thanks man you save my day. I wish I can give 100 up vote to you, – Ironman
this solution works even if you have the latest version. sometimes you may get the error, just redownload and replace with the existing. I dont know why but it works like that – batmaci
yes, yes and yes !!! – Philippe
My android sdk folder doesn't contain a proguard folder, it doesn't even contain a tools folder.... And when I download the latest version of proguard, it doesn't contain a proguard-android.txt file so it errors on Xamarin build. What gives? – Justin
@Justin Create a new Stack Overflow question with more details and I'll try to answer. – Jon Douglas

I was also facing the same issue on my Windows 10 x64 and visual studio 2015. I have set the JDK path to JDK 1.8 under android settings in Visual studio tools ->options ->xamarin ->java development kit location. it was pointing to "C:\Program Files (x86)\Java\jdk1.7.0_55" and I made it to "C:\Program Files\Java\jdk1.8.0_31", and issue has been fixed.

Does changing the path fixed this issue?? – Femil Shajin
No it does not work for me, whether I use Java 7 or Java 8 in VS/Xamarin Studio I get the same error. – Guillaume Perrot
This does not fix the problem, if using ProGuard or Multi-Dex, because those depend on a tool inside android sdk/tools/proguard, as described in Jon Douglas answer. On the other hand, it should fix the problem for anyone not using either ProGuard or Multi-Dex, if they are getting this error trying to use Nougat [API 24], or some package/library that depends on an API 24 feature. – ToolmakerSteve

Simple Answer

According to documentation you need update proguard version (starting from version 5 it support Java 8 ) and make sure you are using jdk1.8

JDK 1.8 - up to API 24+

JDK 1.7 - up to API 23

JDK 1.6 - up to API 20

how to update from package console write this command

PM> Install-Package name.atsushieno.proguard.facebook

or download proguard manually and replace it with current version

YOUR_SDK --> tools --> proguard --> (delete all old files , unzip new version )

Detailed Answer if you enable target android Nogut and you enable Multi-Dex or ProGuard you need use proper ProGuard version (as ToolMakerSteve said they have dependency on ProGuard) so make sure you target java 8 from tools ->options ->xamarin ->java and update ProGuard version

Update Answer

make sure your support library version compatible with target version , if you target

Android 7 (api 24) mean your support library should be 24

Android 7.1 (api 25 ) mean your support library should be 25

to all support library and if you using google play services as well

I had a problem where Proguard was removing the Google Play Services libraries from my app.

In addition to following @Jon Douglas' answer above, I had to add the following lines of text to the proguard-android.txt file found in this folder:

/(Path to your Android SDK Folder)/tools/proguard

-keep public class* { public *; }

Complete proguard-android.txt File

-keep public class* { public *; }

# This is a configuration file for ProGuard.


# 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).
# 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
# file.

-keepattributes *Annotation*
-keep public class
-keep public class

# For native methods, see
-keepclasseswithmembernames class * {
    native <methods>;

# keep setters in Views so that animations can still work.
# see
-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 {
   public void *(android.view.View);

# For enumeration classes, see
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);

-keepclassmembers class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator 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.

# Understand the @Keep support annotation.
-keep class

-keep class * {*;}

-keepclasseswithmembers class * { <methods>;

-keepclasseswithmembers class * { <fields>;

-keepclasseswithmembers class * { <init>(...);

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