2

I am looking into sharing active objects between two processes, however the documentation regarding it is often lackluster and sometimes even incorrect.

Specifically I was looking into sharing a Binder objects via parcels. The documentation states.

Active Objects

An unusual feature of Parcel is the ability to read and write active objects. For these objects the actual contents of the object is not written, rather a special token referencing the object is written. When reading the object back from the Parcel, you do not get a new instance of the object, but rather a handle that operates on the exact same object that was originally written. There are two forms of active objects available.

Binder objects are a core facility of Android's general cross-process communication system. The IBinder interface describes an abstract protocol with a Binder object. Any such interface can be written in to a Parcel, and upon reading you will receive either the original object implementing that interface or a special proxy implementation that communicates calls back to the original object. The methods to use are writeStrongBinder(IBinder), writeStrongInterface(IInterface), readStrongBinder(), writeBinderArray(IBinder[]), readBinderArray(IBinder[]), createBinderArray(), writeBinderList(List), readBinderList(List), createBinderArrayList().

However when receiving the parcel, the object returned is merely a BinderProxy, which cannot be cast to the original class or implement any calls beyond basic IBinder calls. While this is obviously the proxy object referred to in the documentation, I was wondering what the method was for referencing the original object that was alluded to in the same statement.

I was also wondering if there was a source where this topic was more thoroughly explained or documented.

Community
  • 1
  • 1
Beryllium
  • 556
  • 1
  • 7
  • 20

1 Answers1

-2

You should be able to cast the objects to its original class, given that it implement the Parcelable interface correctly. Casting it's just like this:

// in ProcessDataActivity retrieve User 
Intent intent = getIntent();
ParcelableObjectExample usr = (ParcelableObjectExample)
     intent.getParcelableExtra("parcelableExample");

For this to be successful you need to correctly implement the Parcelable interface on ParcelableObjectExample, for this you must:

  1. Implement its describeContents method
  2. Implement its abstract method writeToParcel, which takes the current state of the object and writes it to a Parcel
  3. Add a static field called CREATOR to our class, which is an object implementing the Parcelable.Creator interface
  4. Add a Constructor that takes a Parcel as parameter. The CREATOR calls that constructor to rebuild our object.
InvertedNetwork
  • 200
  • 3
  • Unfortunately, using a parcelable in that manner marshals the class then unmarshals it when it is retrieved meaning that the object is merely being recreated in the new process as opposed to it being an Active Object. – Beryllium Sep 15 '15 at 00:33