How to Perform Minification and Obfuscation with the Jack Compiler

How to perform minification and obfuscation with the JACK compiler?

J.A.C.K. obfuscation does not appear to be supported in the latest released Gradle Plugin (v2.1.0).

If you enable JACK when using the latest v2.1.0 plugin, it will tell you Jack requires Build Tools 24.0.0 or later requiring you to use the preview tools.

Using android gradle v2.2.0-alpha1, Build Tools-v24rc4, Platform Tools-v24rc3, and Sdk Tools-v25.1.7rc1 I was able to get obfuscation to be performed by JACK.

When enabled inside defaultConfig it complained Minifying the variant used for tests is not supported when using Jack., because minifyEnabled true was configured in the debug build.

So, I created a custom build type and enabled it there:

buildTypes {
    ...
    custom {
        minifyEnabled true
        proguardFiles 'proguard-android-JACK.txt-2.2.0-alpha1'
        jackOptions {
            enabled true
        }
    }

There was a problem when using proguardFiles getDefaultProguardFile('proguard-android.txt'). It errorred with: com.android.jack.api.v01.ConfigurationException: Error while parsing ..., . So, I just removed the lines it complained about and then just manually specified my modified configuration file.

Jack and Jill minify equivalent

Nothing I have read suggests that there is any change needed with regard to minifyEnabled true. And that Jack does support it and works with multidex.

From: http://tools.android.com/tech-docs/jackandjill#TOC-Overview

...Jack also handles any requested code minification (shrinking and/or obfuscation). The output is then assembled into an APK file as normal. Including support for multiple dex files if you have enabled that support.

Jack's Shrinking and Obfuscation does not support all of proguard's options however. There is a list here:

http://tools.android.com/tech-docs/jackandjill#TOC-Shrinking-and-Obfuscation-support

How to enable Jack (Java Android Compiler Kit) in android studio

The details on what is required to use Jack and how can be found in the documentation.

Here is the relevant part from the docs that goes in build.gradle on how to use jackOptions and set the compileOptions for java 1.8.

android {
    ...
    defaultConfig {
        ...
        jackOptions {
            enabled true
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

UPDATE

The Jack toolchain is now considered deprecated according to this post and work is being done to natively support Java 8 features as part of the Android build system in the coming weeks according to the post.

The post also mentions that there should be little to no work migrating from Jack to the new method in case you still wanted to try enabling Java 8 features with Jack.

UPDATE 2 Preview Built-in Support

You can now try out the new built-in support for Java 8 using the latest Android Studio preview 2.4 preview 6.

For more information on how to enable it or migrate from Jack or Retrolambda see the documentation.

Error:Jack is required to support java 8 language features

Error:Jack is required to support java 8 language features. Either
enable Jack or remove sourceCompatibility JavaVersion.VERSION_1_8.

The error say that you have to enable Jack.

To enable support for Java 8 in your Android project, you need to configure your build.gradle file like that

android {
  ...

  compileSdkVersion 23
  buildToolsVersion "24rc2"
  defaultConfig {
  ...
    jackOptions {
      enabled true
    }
  }

  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
} 

Crashlytics don't compile when using Jack

Crashlytics task depends on dex task, which will not be created, because Jack does dexing internally. This is most likely something Crashlytics team will have to deal with soon and fix.

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