使用Android支持库和Maven的NoClassDefFoundError

Question

Using the latest version 4.0.0-rc.1 of the Maven Android Plugin, some classes seem to be missing in the build. I get one of those exceptions when I start the app (two possible ways to start the app):

• java.lang.NoClassDefFoundError: android.support.v4.app.TaskStackBuilderHoneycomb
• java.lang.NoClassDefFoundError: android.support.v4.widget.EdgeEffectCompatIcs

Both missing classes are inside support-v4-21.0.0.aar/libs/internal_impl-21.0.0.jar.

My dependency definition:

    <dependency>
        <groupId>com.android.support</groupId>
        <artifactId>support-v4</artifactId>
        <version>21.0.0</version>
        <type>aar</type>
    </dependency>

Is this some configuration error? A bug in the Android Maven plugin?

Answer 1

You need to set the following config in the pom:

<includeLibsJarsFromAar>true</includeLibsJarsFromAar>

So it will look something like this:

<plugin>
    <groupId>com.jayway.maven.plugins.android.generation2</groupId>
    <artifactId>android-maven-plugin</artifactId>
    <extensions>true</extensions>
    <configuration>
        //...
        <includeLibsJarsFromAar>true</includeLibsJarsFromAar>
        //... rest of config
    </configuration>    
</plugin>

The reason for that change is that Google decided to put jars inside the aar which is a bad practice of dependencies. If you want to substitute the version or something else it is not currently possible. In short it makes dependencies much more difficult to manage.

This setting is set to false by default to discourage this behavior of creating aar's with jar's inside the libs folder.

Update:

Using the latest Android-Maven-Plugin (Now 4.1.1 soon 4.2.0) this flag is set to true by default so you do not need to add it anymore.

Answer 2

I found a temporary solution:

• cp support-v4-21.0.0.aar ~/Desktop
• cd ~/Desktop && mv support-v4-21.0.0.aar support-v4-21.0.0.jar
• jar xf support-v4-21.0.0.jar

then pull out internal_impl-21.0.0.jar from libs folder and upload to your own artifactory if you have any, and modify your pom file it should work, if you don't have your own artifactory then add it into classpath.

This works for me.

Answer 3

Are you including a jar file with a "provided" scope for the aar dependency? I think I found the same bug and have the same issue.

https://github.com/jayway/maven-android-plugin/issues/485