title: How can I start two asynchronous threads which join to common execution once both are complete?
body: <p>I'm looking for a design pattern or approach for the following scenario.  I wish to kick off two separate background threads for data retrieval from different sources.  I then want one method (on the UI thread) to be called once both background threads have completed their work.  As the data from the two sources must be combined to be useful, I must wait until both have finished retrieving before manipulating the data.  How can I achieve this on the Android platform?</p>