Unable to generate signed APK with proguard enabled when Joda Time is used

Question

I tried to build a signed APK. I am also using proguard. In my application I used JodaTime for some purposes. I used joda-time-2.7.jar in there. First I could get a signed APK without enabling proguard, there were no errors. Then I enabled proguard and tried to generate the APK but I it generated errors. Below are the errors generated.

Warning:org.joda.time.LocalDateTime: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.LocalTime: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.LocalTime: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.Minutes: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Minutes: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.MonthDay: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.MonthDay: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.Months: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Months: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.MutableDateTime: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.MutablePeriod: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Period: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Seconds: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Seconds: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.Weeks: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Weeks: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.YearMonth: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.YearMonth: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.Years: can't find referenced class org.joda.convert.FromString
Warning:org.joda.time.Years: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.base.AbstractDateTime: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.base.AbstractDuration: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.base.AbstractInstant: can't find referenced class org.joda.convert.ToString
Warning:org.joda.time.base.AbstractPeriod: can't find referenced class org.joda.convert.ToString
Warning:there were 37 unresolved references to classes or interfaces.
     You may need to add missing library jars or update their versions.
     If your code works fine without the missing classes, you can suppress
     the warnings with '-dontwarn' options.
     (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
Exception while processing task java.io.IOException: Please correct the above warnings first.
  at proguard.Initializer.execute(Initializer.java:473)
  at proguard.ProGuard.initialize(ProGuard.java:233)
  at proguard.ProGuard.execute(ProGuard.java:98)
  at proguard.gradle.ProGuardTask.proguard(ProGuardTask.java:1074)
  at com.android.build.gradle.tasks.AndroidProGuardTask.doMinification(AndroidProGuardTask.java:139)
  at com.android.build.gradle.tasks.AndroidProGuardTask$1.run(AndroidProGuardTask.java:115)
  at com.android.builder.tasks.Job.runTask(Job.java:48)
  at com.android.build.gradle.tasks.SimpleWorkQueue$EmptyThreadContext.runTask(SimpleWorkQueue.java:41)
  at com.android.builder.tasks.WorkQueue.run(WorkQueue.java:227)
  at java.lang.Thread.run(Thread.java:745)

Below is my build.gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        applicationId "com.theacetechnologies.voicetype"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
    compile files('libs/joda-time-2.7.jar')
}

Any idea why I am unable to generate the singed APK when proguard is enabled? I believe this is something related to Joda Time as well, because I have generated proguard enabled signed APKs previously without JODA time.

Answer 1

Add these lines to your proguard file

-dontwarn org.joda.convert.**
-dontwarn org.joda.time.**
-keep class org.joda.time.** { *; }
-keep interface org.joda.time.** { *;}