If you need to do a Facebook Connect implementation in Java, please give it a try and let me know what you think!

public interface Operation<V, E extends Throwable> {
  V execute() throws E;
}

…would love to see this (as well as a Pair<A,B> class) in a future cut of Java.

There isn’t much to the example – just a single controller and datasource. It’s pretty straightforward to bolt on additional functionality like a “load more” button (just read the TTCatalog and Three20 source) and hook into the other nice table features Three20 offers out of the box. Until better docs are available, hopefully this example can serve as a starting point for your own experimentation. Feedback is welcome!

Some screenshots so you know what you’re getting…first, the controller (registered as a datasource delegate) gets a notification that the datasource is in a loading state – this view is then automatically shown by the framework:

Second, the data has been loaded and the datasource has notified the controller that it’s ready. The controller then retrieves data from the datasource and displays it:

(I’m using a feed provided by the Yahoo Image Search Service API: here’s the raw JSON.)

Update, October 3 9:30 AM EDT
It’s come to my attention that some people are still using this code – please don’t! It was based on three20 as it existed back in March/April 2009 and is now very much out-of-date. If you’re looking for current and correct three20 sample code, Keith Lazuka’s github has what you need. Thanks!

One approach to this problem is to subclass a canned datasource, which gets us a bunch of stuff for free right off the bat:

@interface MyDataSource : TTListDataSource<TTURLRequestDelegate> {
 @private
  BOOL _loading;
  BOOL _loaded;
}

You’ll want to provide meaningful implementations of accessors like loadedTime:, isLoading:, isLoadingMore:, isLoaded:, etc. Your controller will query the datasource using those selectors to know what state to show (e.g. loading, error, data, no data).

Write a load:nextPage: implementation that hits the network:

- (void)load:(TTURLRequestCachePolicy)cachePolicy nextPage:(BOOL)nextPage {
  TTURLRequest *request =
   [TTURLRequest requestWithURL:@"http://test.com/test.json" delegate:self];

  request.cachePolicy = cachePolicy;
  request.response = [[[TTURLDataResponse alloc] init] autorelease];
  request.httpMethod = @"GET";
  [request send];
}

Write a requestDidFinishLoad: implementation that pulls JSON out of the response (maybe using Stig Brautaset’s very nice JSON framework) and let your controller know that data’s available via dataSourceDidFinishLoad:.

- (void)requestDidFinishLoad:(TTURLRequest*)request {
  TTURLDataResponse *response = request.response;
  NSString *json = [[NSString alloc] initWithData:response.data encoding:NSUTF8StringEncoding];

  // Load up self.items with json data however you'd like

  [json release];

  _loading = NO;
  _loaded = YES;  

  [self dataSourceDidFinishLoad];
}

Don’t forget to implement requestDidStartLoad:, request:didFailLoadWithError:, and requestDidCancelLoad: and have them notify any interested delegates of the request’s status. Here’s an example:

- (void)request:(TTURLRequest*)request didFailLoadWithError:(NSError*)error {
  _loading = NO;
  _loaded = YES;
  [self dataSourceDidFailLoadWithError:error];
}

In your controller, createDataSource: might look like this:

- (id<TTTableViewDataSource>)createDataSource {
  MyDataSource *dataSource = [[[MyDataSource alloc] init] autorelease];
  [dataSource.delegates addObject:self];
  [dataSource load:TTURLRequestCachePolicyDefault nextPage:NO];
  return dataSource;
}

Have fun out there.

Update, April 11 10:30 AM EDT
I’ve added a new post with a downloadable example project and (finally) cleaned up the above code. I apologize for previous typos; I really should make sure the code I post actually compiles instead of writing/tweaking it in a wordpress edit window.

Update, October 3 9:30 AM EDT
It’s come to my attention that some people are still using this code – please don’t! It was based on three20 as it existed back in March/April 2009 and is now very much out-of-date. If you’re looking for current and correct three20 sample code, Keith Lazuka’s github has what you need. Thanks!

Needs more background-repeat: no-repeat;

Luckily, I found this guy (girl?) in the same boat, who figured out that you just need to flip a system property to get correct behavior – in my case, passing in the VM argument -Djava.net.preferIPv4Stack=true on Tomcat startup.

The reason I mention this is because Amazon’s Elastic Block Storage was released today – finally, persistent non-S3 storage inside the compute cloud. We could slap Hadoop and a database and webserver on that bitch and be ready to roll. Great stuff, really excited to see old-fashioned webhosting die.