Problem unmarshalling parcelables

Question

I\'ve got a few classes that implement Parcelable and some of these classes contain each other as properties. I\'m marshalling the classes into a Parcel to pass them between

Answer 1

I got this exception because I was missing a constructor. The same must be done for all classes that implement Parcelable:

// add new constructor
@RequiresApi(Build.VERSION_CODES.N)
private LocationType(Parcel dest, ClassLoader loader) {
    super(dest, loader);
    locid = dest.readInt();
    desc  = dest.readString();
    dir   = dest.readString();
    lat   = dest.readDouble();
    lng   = dest.readDouble();
}

public static final Creator<LayoverType> CREATOR = new ClassLoaderCreator<LayoverType>() {

    // add createFromParcel method with ClassLoader
    @Override
    public LayoverType createFromParcel(Parcel in, ClassLoader loader)
    {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.N ? new LayoverType(in, loader) : new LayoverType(in);
    }

    public LayoverType createFromParcel(Parcel in) {
        // call other createFromParcel method.    
        return createFromParcel(in, null);
    }

    public LayoverType[] newArray(int size) {
        return new LayoverType[size];
    }
};

Answer 2

I had the same problem with the following setup: some handler creates a Message and sends its over a Messenger to a remote service.

the Message contains a Bundle where I put my Parcelable descendant:

final Message msg = Message.obtain(null, 0);
msg.getData().putParcelable("DOWNLOADFILEURLITEM", downloadFileURLItem);

messenger.send(msg);

I had the same exception when the remote service tried to unparcel. In my case, I had overseen that the remote service is indeed a separate os process. Therefore, I had to set the current classloader to be used by the unparcelling process on the service side:

final Bundle bundle = msg.getData();
bundle.setClassLoader(getClassLoader());

DownloadFileURLItem urlItem = (DownloadFileURLItem)
bundle.getParcelable("DOWNLOADFILEURLITEM");

Bundle.setClassLoader sets the classloader which is used to load the appropriate Parcelable classes. In a remote service, you need to reset it to the current class loader.

Answer 3

If you have an Object with a property of type of List objects you should pass the class loader when you read the property for example:

public class Mall implements Parcelable {

    public List<Outstanding> getOutstanding() {
        return outstanding;
    }

    public void setOutstanding(List<Outstanding> outstanding) {
        this.outstanding = outstanding;
    }        

    protected Mall(Parcel in) {
        outstanding = new ArrayList<Outstanding>();
        //this is the key, pass the class loader
        in.readList(outstanding, Outstanding.class.getClassLoader());
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeList(outstanding);
    }

    public static final Parcelable.Creator<Mall> CREATOR = new Parcelable.Creator<Mall>() {
        public Mall createFromParcel(Parcel in) {
            return new Mall(in);
        }

        public Mall[] newArray(int size) {
            return new Mall[size];
        }
    };
}

Note: Is important that the class Outstanding implements the Parceable interface.

Answer 4

I am not very familiar with Parcelable but if it's anything like Serialization each call to write an object that implements the interface will cause a recursive call to writeToParcel(). Therefore, if something along the call stack fails or writes a null value the class that initiated the call may not be constructed correctly.

Try: Trace the writeToParcel() call stack through all the classes starting at the first call to writeToParcel() and verify that all the values are getting sent correctly.