Put an object in Handler message

Question

I need to download an image from the internet, in a different thread,
and then send that image object in the handler message, to the UI thread.

I already have this:

... Message msg = Message.obtain();  Bundle b = new Bundle(); b.putParcelable("MyObject", (Parcelable) object); msg.setData(b);  handler.sendMessage(msg); 

And when I receive this message, I want to extract the object:

... public void handleMessage(Message msg) {     super.handleMessage(msg);      MyObject objectRcvd = (MyObject) msg.getData().getParcelable("IpTile");     addToCache(ipTile);     mapView.invalidate(); } 

But this is giving me:

...java.lang.ClassCastException... 

Can anyone help?

And by the way, is this the most efficient way
to pass an object to the UI Thread?

Thank you all!

Answer 1

I know I'm late to the party, but there is an easier way if you are using the service within a single process. You can attach any arbitrary Object to your Message using this line:

msg.obj = new CustomObject() // or whatever object you like 

This is working well for me in my current projects.
Oh, and I'm moving away from using AsyncTask objects, as I believe they increase code coupling too much.

Answer 2

First: Where exactly do you get the exception? When putting the instance into the bundle, or upon retrieving it?

I believe your mixing things up. When creating your bundle, you write

b.putParcelable("MyObject", (Parcelable) object); 

So you are assigning the instance "objet " to the key "MyObject". But when retrieving your instance you write:

MyObject objectRcvd = (MyObject) msg.getData().getParcelable("IpTile"); 

Here, you are retrieving an instance from the key "IpTile". Note that "IpTile" != "MyObject". Try using the following to retrieve the object:

MyObject objectRcvd = (MyObject) msg.getData().getParcelable("MyObject"); 

or the other way around, try replacing your code which puts the instance into the bundle with this:

b.putParcelable("IpTile", (Parcelable) object); 

Another few points to check:

• Does the class MyObject implement Parcelable? (I suppose so, otherwise you wouldn't be able to compile)
• Does the variable object contain an instance which implements Parcelable?