[Android SDK] Throw a custom exception from a service to an activity

Question

Hi,

I'm currently working on an XMPP app' on Android and I'm pondering about the best way to throw a different type of Exception than a RemoteException to my activity from my service.

As it seems impossible to throw another thing than a RemoteException using IPC (you can't declare to throw anything in your .aidl), I just see two solutions:

• Create a listener for my activity to listen on my custom XMPP exception, which in fact will not be thrown but just sent as a usual object implementing the Parcelable protocol.

• Catch my XMPPException and throw a RemoteException (with a content updated with my XMPPException) - But in that case, how could I know on my activity if it's an XMPP or a real RemoteException ? By tagging the name of the exception and parsing it on my activity ? It would be really gore.

Do you have any idea ? Did I miss something from the SDK documentation ?

Thanks.

Answer 1

If #1 means what I think it does, I'd use that -- have the service catch the exception and call a method on an AIDL-defined callback object created and supplied by the activity.

You can see an example of that technique in this client and service project, from one of my books.

Answer 2

It looks like we can throw custom exceptions derived from RemoteException. So you can have XMPPRemoteException, or just a generic MyRemoteException that will hold the original exception. Below is a demo for the second case:

Server:

try {
    ...
}
catch(XMPPException e) {
    throw new MyRemoteException(e);
}

Client:

try {
    service.someCall();
}
catch(MyRemoteException e) {
    rethrow(e);
}

Helper method:

private void rethrow(MyRemoteException e) throws Exception {
    if(e.innerException instanceof XMPPException)
        throw (XMPPException)e.innerException;
    else
        throw e.innerException;
}

Exception:

public class MyRemoteException extends RemoteException {
    private static final long serialVersionUID = 1L;
    public Exception innerException;

    public MyRemoteException() {}

    public MyRemoteException(Exception innerException) {
        this.innerException = innerException;
    }
}