Usage of Java 8 with jack compiler on Android Pre L devices

Question

I'm currently updating my app to work with java 8. Therefore I'm using the jack compiler.

That works perfectly for every device with Android 5.0 or higher. On older devices with Pre Lollipop versions, I'm getting the following exception:

Caused by: java.lang.ClassNotFoundException: Didn't find class "de.gelbeseiten.android.GelbeSeitenApplication" on path: DexPathList[[zip file "/data/app/de.gelbeseiten.android-1.apk"],nativeLibraryDirectories=[/data/app-lib/de.gelbeseiten.android-1, /vendor/lib, /system/lib, /system/lib/arm]] at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56) at java.lang.ClassLoader.loadClass(ClassLoader.java:497) at java.lang.ClassLoader.loadClass(ClassLoader.java:457) at android.app.Instrumentation.newApplication(Instrumentation.java:981) at android.app.LoadedApk.makeApplication(LoadedApk.java:511) at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4722)  at android.app.ActivityThread.access$1600(ActivityThread.java:172)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1368)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:146)  at android.app.ActivityThread.main(ActivityThread.java:5653)  at java.lang.reflect.Method.invokeNative(Native Method)  at java.lang.reflect.Method.invoke(Method.java:515)

I'm 99% sure, the change to Java 8 is the reason for that, as that does happen if I check out the current public version and change nothing except including java 8.

Unfortunately I can't find anything in google for this. On the google android site for the java 8 support, nothing's written about a minimum android version needed. https://developer.android.com/guide/platform/j8-jack.html

I don't think the complete build.gradle file is useful, but here's a snippet:

android {
    useLibrary 'org.apache.http.legacy'

    defaultConfig {
        [...]
        multiDexEnabled = true
        jackOptions {
            enabled true
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    packagingOptions {
        exclude 'META-INF/DEPENDENCIES.txt'
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/NOTICE.txt'
        exclude 'META-INF/NOTICE'
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/DEPENDENCIES'
        exclude 'META-INF/notice.txt'
        exclude 'META-INF/license.txt'
        exclude 'META-INF/dependencies.txt'
        exclude 'META-INF/LGPL2.1'
    }
}

I've never manually changed the proguard-rules.txt, but here it is:

# Add project specific ProGuard rules here.
# By teilnehmer, the flags in this file are appended to flags     specified
# in /Applications/Android Studio.app/sdk/tools/proguard/proguard-android.txt
# You can edit the include path and order by changing the ProGuard
# include property in project.properties.
#
# 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 *;
#}

##---------------Begin: proguard configuration common for all Android apps ----------
-dontobfuscate
-optimizationpasses 5
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontskipnonpubliclibraryclassmembers
-dontpreverify
-verbose
-dump class_files.txt
-printseeds seeds.txt
-printusage unused.txt
-printmapping mapping.txt
-optimizations             !code/simplification/arithmetic,!field/*,!class/merging/*

-allowaccessmodification
-keepattributes *Annotation*
-renamesourcefileattribute SourceFile
-keepattributes SourceFile,LineNumberTable
-repackageclasses
-libraryjars libs

# The official support library.
-keep class android.support.v4.app.** { *; }
-keep interface android.support.v4.app.** { *; }

# Library JARs.
-keep class de.greenrobot.dao.** { *; }
-keep interface de.greenrobot.dao.** { *; }
-keep class org.joda.** { *; }
-keep interface org.joda.** { *; }
-keep class com.loopj.android.http.** { *; }
-keep interface com.loopj.android.http.** { *; }

-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
-dontnote com.android.vending.licensing.ILicensingService

# Espress: java.lang.NoSuchMethodError:     android.support.test.espresso.Espresso
-keep class android.support.v7.widget.RecyclerView { *; }

# adjust
-keep class com.adjust.sdk.** { *; }
-keep class com.google.android.gms.common.** { *; }
-keep class com.google.android.gms.ads.identifier.** { *; }

-keep class com.adjust.sdk.plugin.MacAddressUtil {
    java.lang.String getMacAddress(android.content.Context);
}
-keep class com.adjust.sdk.plugin.AndroidIdUtil {
    java.lang.String getAndroidId(android.content.Context);
}
-keep class com.google.android.gms.common.ConnectionResult {
    int SUCCESS;
}
-keep class com.google.android.gms.ads.identifier.AdvertisingIdClient {
    com.google.android.gms.ads.identifier.AdvertisingIdClient$Info getAdvertisingIdInfo (android.content.Context);
}
-keep class com.google.android.gms.ads.identifier.AdvertisingIdClient$Info {
    java.lang.String getId ();
    boolean isLimitAdTrackingEnabled();
}

#keep all classes that might be used in XML layouts
-keep public class * extends android.view.View
-keep public class * extends android.app.Fragment
-keep public class * extends android.support.v4.Fragment

# Explicitly preserve all serialization members. The Serializable interface
# is only a marker interface, so it wouldn't save them.
-keepclassmembers class * implements java.io.Serializable {
static final long serialVersionUID;
private static final java.io.ObjectStreamField[] serialPersistentFields;
private void writeObject(java.io.ObjectOutputStream);
private void readObject(java.io.ObjectInputStream);
java.lang.Object writeReplace();
java.lang.Object readResolve();
}

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

-keepclassmembers class fqcn.of.javascript.interface.for.webview {
   public *;
}


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

# Preserve all native method names and the names of their classes.
-keepclasseswithmembernames class * {
native <methods>;
}


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

# Preserve static fields of inner classes of R classes that might be     accessed
# through introspection.
-keepclassmembers class **.R$* {
public static <fields>;
}

# Preserve the special static methods that are required in all     enumeration classes.
-keepclassmembers enum * {
public static **[] values();
public static ** valueOf(java.lang.String);
}

-keep public class * {
public protected *;
}

-keep class * implements android.os.Parcelable {
public static final android.os.Parcelable$Creator *;
}
##---------------End: proguard configuration common for all Android apps ----------

##---------------Begin: proguard configuration for Gson ----------
# Gson uses generic type information stored in a class file when working with fields. Proguard
# removes such information by teilnehmer, so configure it to keep all of it.
-keepattributes Signature

# For using GSON @Expose annotation
-keepattributes *Annotation*

# Gson specific classes
-keep class sun.misc.Unsafe { *; }
#-keep class com.google.gson.stream.** { *; }

# Application classes that will be serialized/deserialized over Gson
-keep class com.google.gson.examples.android.model.** { *; }

##---------------End: proguard configuration for Gson ----------

Stackoverflow displays part of the file as a comment but in my proguard file in Android Studio that's not the case.

Soo...does anyone have more information on this topic? Or maybe even a fix to get the app running on Pre L devices as well?

Thanks in advance!
Ben

Answer 1

First of all, if you are using Instant Run disable it. Not works with Java 8 at the moment.

Also, you should add:

-keep class de.gelbeseiten.android.** { *; }

Also make sure that de.gelbeseiten.android.GelbeSeitenApplication is in your main dex file (probably is classes.dex).

If not here, you should do some like this:

android {
    buildTypes {
        debug {
            ...
            multiDexEnabled true
            multiDexKeepFile file('multidex_keep_file.txt')
        }
    }
}

And in your multidex_keep_file.txt you needs to specify which classes will be in your main dex.

 de/gelbeseiten/android/GelbeSeitenApplication.class
 de/gelbeseiten/android/MainActivity.class (for example)

This text file that specifies additional classes that will be compiled into the main dex file.

Classes specified in the file are appended to the main dex classes computed using aapt.

If set, the file should contain one class per line, in the following format: com/example/MyClass.class