How to generate a jar file for a java project and use the jar in an android project

Question

I am trying to generate a jar file for a java project and then references the jar file in an android project. As a test, I create a simple java project only containing the following class

package test;
public class Test {
public static void hello(){
    System.out.println();
}
public static void main(String[] args){
    hello();
}

}

I export this project an executable Jar file under Eclipse. Then I copy this jar file into the "libs" folder of an android project, so the jar file occurs in the private library and I check the box of private libary under the "Order and Export" tab. I reference the jar file by adding the following statement into the onCreate() of the main activity of the android project

  Test.hello(); //reference the jar file

However, when I run the Android project, I get the

java.lang.NoClassDefFoundError: test.Test

error. The full error track trace is below

 10-17 23:14:52.976: E/AndroidRuntime(16725): FATAL EXCEPTION: main
 10-17 23:14:52.976: E/AndroidRuntime(16725): java.lang.NoClassDefFoundError: test.Test
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at      
  com.skyhookwireless.samples.wpsapitest.WpsApiTest.onCreate(WpsApiTest.java:71)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at    
  android.app.Activity.performCreate(Activity.java:4470)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.app.ActivityThread.access$600(ActivityThread.java:128)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
 android.os.Handler.dispatchMessage(Handler.java:99)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at 
  android.os.Looper.loop(Looper.java:137)
  10-17 23:14:52.976: E/AndroidRuntime(16725):  at     
   android.app.ActivityThread.main(ActivityThread.java:4517)
    10-17 23:14:52.976: E/AndroidRuntime(16725):    at  
    java.lang.reflect.Method.invokeNative(Native Method)
   10-17 23:14:52.976: E/AndroidRuntime(16725):     at 
  java.lang.reflect.Method.invoke(Method.java:511)
  10-17 23:14:52.976: E/AndroidRuntime(16725):  at          
  com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980) 
  10-17 23:14:52.976: E/AndroidRuntime(16725):  at  
  com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
 10-17 23:14:52.976: E/AndroidRuntime(16725):   at    
    dalvik.system.NativeStart.main(Native Method)

Attached are the screenshots of the order and export tab and the jars contained in each library.

Does anyone know how I can correct this?

I've read couple of posts (e.g. this) on this site regarding the NoClassDefFoundError and tried the solutions listed in comments or answers. But no one solves my problem in this simple scenario.

Did you follow the [android documentation](http://developer.android.com/tools/projects/index.html) on this topic? I'm using those guidelines with no problems. — Alfredo Cavalcanti, Oct 18 '13 at 03:01
i've read the article you linked. but it only talks about android library projects and does not mention how to make java projects as libraries, does it? — sma, Oct 18 '13 at 03:12
Can you share screen shots of Java Build Path>Order and Export? Have you tried checked Android Dependencies? — Amit Gupta, Oct 18 '13 at 05:21
i think this is a common use case, surprised that no applicable answer occurs yet — sma, Oct 18 '13 at 15:56

score 0 · Answer 1 · answered Oct 18 '13 at 03:07

0

I feel the main activity of your project and test class are being loaded by separate classloaders. Take a look at this to figure out where you might be missing it.

http://javareferencegv.blogspot.com/2013/10/debugging-javalangnoclassdeffounderror.html

answered Oct 18 '13 at 03:07

Gaurav Varma

1,939
4
18
36

nice article, but still not helpful for my problem at hand – sma Oct 18 '13 at 03:22
add the jar containing Test class to your classpath and try if that helps – Gaurav Varma Oct 18 '13 at 03:25
Did you see any further error or exception in stacktrace.. may be a ClassNotFoundException or ExceptionInInitializerError? – Gaurav Varma Oct 18 '13 at 03:39

score 0 · Answer 2 · answered Oct 18 '13 at 03:11

0

You can do it by following steps , this is for making jar from android library project

$ cd your_project_path
$ android update project -p .
$ ant jar

answered Oct 18 '13 at 03:11

ayon

2,150
2
16
31

score 0 · Answer 3 · answered Oct 18 '13 at 03:39

0

Why don't you import your Java project into Android workspace and then use it as a library in your Android project? This should resolve your issue.

answered Oct 18 '13 at 03:39

VikramV

1,061
2
11
27

I did. Makes no difference – sma Oct 18 '13 at 15:37

score 0 · Answer 4 · edited May 23 '17 at 12:33

0

I do not think it is possible for the Dalvik VM to run Java bytecode. And also your Java JAR does not contain any .dex files, the classes inside it would not be found.

See this answer for info on DEX format

You could convert your Java JAR into an Android JAR. Or add your Java sources into your Android project, even referencing the same source files as your Java project...

edited May 23 '17 at 12:33

Community

1
1

answered Feb 01 '17 at 21:30

Usagi Miyamoto

5,721
1
16
28

How to generate a jar file for a java project and use the jar in an android project

4 Answers4