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So I run into this problem today. I got an exception saying 

"NoClassDefFoundException" class com.example.app.MainClass$3

I know what this exception means so first I looked inside classes.jar file located in /app/build/intermediates/exploded-aar/$packageName%/%versionName%/jars.

There I found the "missing" class with exactly the same signature: MainClass$3. So it WAS generated. Then on my smartphone I went to /data/app/%packageName%/ and looked inside base.apk file. Inside it I found a file named classes.dex. I opened it with Notepad++ and I found mentioning of my MainClass$3 there as well! Why this class could not be found? What else should I check? I cannot post original exception messages nor files cause it's commercial, but I'll try to clarify things as much as I can if needed.

UPDATE #1: There is something I think I need to add. The odd thing about all of this is that this class is the only one that cannot be found from the whole library. It's not new, I added it long time ago, so I just thought, maybe some exception that occurred while running some code from that class causing this error?

UPDATE #2: I debugged my app and saw the strangest thing ever: I was able to call constructor of the problematic class with arguments and the object was SUCCESSFULLY CREATED. Then I called a method of the class and got this exception. Here is the method I call

public Observable<String> getSnapshotTaker() {
        int a = 1;
        Observable<String> snapshotTaker = Observable.create(new Observable.OnSubscribe<String>() {
            @Override
            public void call(Subscriber<? super String> subscriber) {
                queueSnapshot(true, 0, subscriber);
            }
        });
        return snapshotTaker;
    }

I inserted

int a = 1;

for debugging purpose. App crashes with the exception on the second line of the method, where I'm trying to create an Observable. So, it looks like it's not the class SnapshotManager which is causing the crash but rather this Observable. But why the exception message looks like this then?

UPDATE #3: Here is the stack trace:

E/AndroidRuntime: FATAL EXCEPTION: main

 java.lang.NoClassDefFoundError: com.test.pack.SnapshotManager$3
    at com.test.pack.SnapshotManager.getSnapshotTaker(SnapshotManager.java:370)
    at com.test.pack.CameraPresenter.takePhoto(CameraPresenter.java:31)
    at com.test.pack.MainActivity$MainShutterClickListener.onClick(MainActivity.java:1100)
    at android.view.View.performClick(View.java:5204)
    at android.view.View$PerformClick.run(View.java:21153)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
jotik
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Sergey Maslov
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1 Answers1

5

I figured out the source of the problem. First of all I noticed that NoClassDefFound exception was pointing at a wrong class. I mean it was not SnapshotManager who's "def" was not found but the Observable class from RxJava library. This is what was causing the exception:

  • Main project which depends on a library I made.
  • The library which depends on rxjava
  • Main project calls some code from the library that uses rxjava classes and, as far as the main project has no rxjava dependencie, it crashes.

Solution is simple: if you have a library project with some external dependencies you should mention those dependencies in your main project as well. I know that it's not the best solution and that there might be a way not to do this, but this is what I came up with.

Sergey Maslov
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