Android: ClassNotFoundException when passing serializable object to Activity

Question

I have a few crash report logs from android market similar to this:

Exception class: java.lang.ClassNotFoundException

Source method: PathClassLoader.findClass()

java.lang.RuntimeException: Unable to start activity ComponentInfo{my.app.package/my.app.package.MyActivity}: java.lang.RuntimeException: Parcelable encounteredClassNotFoundException reading a Serializable object (name = my.app.package.a.ae)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2833)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2854)
at android.app.ActivityThread.access$2300(ActivityThread.java:136)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2179)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:143)
at android.app.ActivityThread.main(ActivityThread.java:5068)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.RuntimeException: Parcelable encounteredClassNotFoundException reading a Serializable object (name = my.app.package.a.ae)
at android.os.Parcel.readSerializable(Parcel.java:1951)
at android.os.Parcel.readValue(Parcel.java:1822)
at android.os.Parcel.readMapInternal(Parcel.java:2008)
at android.os.Bundle.unparcel(Bundle.java:208)
at android.os.Bundle.getBundle(Bundle.java:1078)
at android.app.Activity.onRestoreInstanceState(Activity.java:861)
at android.app.Activity.performRestoreInstanceState(Activity.java:835)
at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2811)
... 11 more
Caused by: java.lang.ClassNotFoundException: my.app.package.a.ae
at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:235)
at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:2590)
at java.io.ObjectInputStream.readNewClassDesc(ObjectInputStream.java:1846)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:826)
at java.io.ObjectInputStream.readNewObject(ObjectInputStream.java:2066)
at java.io.ObjectInputStream.readNonPrimitiveContent(ObjectInputStream.java:929)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2285)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2240)
at android.os.Parcel.readSerializable(Parcel.java:1945)
... 19 more
Caused by: java.lang.NoClassDefFoundError: my.app.package.a.ae
... 29 more
Caused by: java.lang.ClassNotFoundException: my.app.package.a.ae in loader dalvik.system.PathClassLoader[.]
at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
... 29 more 

Please note that I am using proguard -> that's why the "missing" class name is "a.ae".
Actually, "a.ae" is the name proguard gave to the class "MyObject", which is shown below.

Any ideia on why this happens?

I don't think it has to do with proguard, because if it was a problem caused by proguard class renaming, it should happen all times and I would be able to reproduce this issue myself.

Does it have to do with passing a serializable object to MyActivity?
In MyActivity I have

public void onCreate(Bundle savedInstanceState) {  
     myObj = (MyObject) getIntent().getSerializableExtra("nameOfMyObject");  
//here I am trying to read myObj's properties and app seems to crash here  

}

MyObject is just an entity with several types of class members, ex:
public class MyObject implements Serializable {

    /** Generated serialVersionUID */
    static final long serialVersionUID = -267025879233327409L;

    static final String CONSTANT1 = "xpto";

    LinkedHashMap<String, Object> components;

    ArrayList<String> prop1;

    (...)
}

I am starting MyActivity with:

MyObject obj = new MyObj(stuff);
Intent intent;
intent = new Intent(CurrentActivity.this, MyActivity.class);
intent.putExtra("nameOfMyObject",  obj);
CurrentActivity.this.startActivity(intent);

Do you think it has to do with the way the object is being passed (as a serializable extra)?
In the case that I don't find any other solution I think I will "serialize" the object myself to a String and then pass the String extra. What do you think about this?

EDIT: I have tried to reproduce this issue, without success, in the emulator and in the following devices:

-Motorola Milestone 2 Android 2.2
-Samsung Galaxy Tab Android 2.2
-Vodafone 845 Android 2.1
-HTC Tatoo Android 1.6
-Xperia X10 Android 1.6
-Nexus One Android 2.2
-Google G1 Android 1.5

Any new ideas?

Dragoman

Is you object serializable at all? – Cardialgia

We need some code to see what you are trying to do... – Serration

@Flo: Yes, my object is Serializable – Dragoman

@Beasly: public void onCreate(Bundle savedInstanceState) { myObj = (MyObject) getIntent().getSerializableExtra("nameOfMyObject"); //here I am trying to read myObj's properties and app seems to crash here } – Dragoman

Write a quick test class which serializes and then un-serializes your object just to confirm there's not a class further down in the chain that's causing the problem. – Travers

@John J Smith I have done that and and run passed the Serializable object thousands of times but I was unable to reproduce the issue :S I guess that it is some kind of rare occurrence that only happens in some devices / situations – Dragoman

Answer 1

Finally reached a conclusion on this issue: it was being caused by Proguard, or more specifically, because I didn't have a propper Proguard configuration.

It turns out Proguard was changing my Serializable's classes names, which makes Class.forName(className) fail.

I had to reconfigure my proguard.cfg file adding the following lines:

-keep class * implements java.io.Serializable

-keepclassmembers class * implements java.io.Serializable {
    static final long serialVersionUID;
    private static final java.io.ObjectStreamField[] serialPersistentFields;
    !static !transient <fields>;
    !private <fields>;
    !private <methods>;
    private void writeObject(java.io.ObjectOutputStream);
    private void readObject(java.io.ObjectInputStream);
    java.lang.Object writeReplace();
    java.lang.Object readResolve();
}

Dragoman

after almost 2 years you saved my day buddy .. thanks +1. I also appreciate your attitude towards posting your own answer – Pickaback

Official ProGuard explaination: proguard.sourceforge.net/manual/examples.html#serializable – Jenellejenesia

what if proguard is not enabled? and this error is still occurring – Him

I also faced this issue in some Samsung devices while Progurd is disabled. – Ubangi

Answer 2

You should look into implementing Parcelable. These two links should get you started: http://developer.android.com/reference/android/os/Parcel.html http://developer.android.com/reference/android/os/Parcelable.html

Ultimogeniture

This was how I finally resolved a similar crash after trying the Proguard changes. – Sedgemoor

Answer 3

LinkedHashMap doesn't implement Serializable so this may be causing the error. Try either implementing a small test to serialize this class or try removing the LinkedHashMap and see if the error persists.

Cataract

Thanks for the tip. I'll try this, but the main issue is that I'm not able to reproduce the problem anyway, so I can't even be sure that any solution that I find effectively solves the issue :( – Dragoman