Mark Murphy - Beginning Android

Enter AsyncTask.

AsyncTaskmanages a work queue with a thread pool, so you do not need to implement that yourself. Moreover, all of the communication between foreground and background threads are handled for you. All you need to do is override a few methods to describe what you want done in the background or in the foreground.

To create an AsyncTask, simply extend one anonymously, like you might do to create a Runnable. You can then override whatever methods you need to for the pattern you want:

• Override onPreExecute()to specify something that should be done on the UI thread when the task is started

• Override doInBackground()to indicate the work that should be done in the background thread

• Override onProgressUpdate()to update your progress on the UI thread when doInBackground()calls publishProgress()(e.g., update a ProgressBar)

• Override onPostExecute()to do whatever work needs to be done on the UI thread after the background work is complete

Using your custom AsyncTaskis then a matter of calling execute()on one of its instances, such as one might call run()on a Runnable.

Of course, there are many, many more things added to Android 1.5 beyond what is covered earlier. Here is a quick recap of other capabilities you will be able to take advantage of in Android 1.5.

Android 1.1 debuted Google Voice Search, where you could tap on a microphone icon text to the search field on the home screen, speak your search request, and have the search conducted on what you said.

Android 1.5 opens this up to be available to all applications. You can start an activity using an Intent using the RecognizerIntent.ACTION_RECOGNIZE_SPEECHaction and have the converted text supplied to you in response via onActivityResult().

A common pattern, particularly when using AlarmManagerfor scheduling periodic background work, is to have a service that implements onStart()and forks a background thread to do the desired work. This runs the risk of forking too many threads, though, and managing your own work queue and thread pool can be annoying.

The IntentServiceclass wraps that pattern up for you. All you do is implement onHandleIntent(), and Android will process all inbound Intents via a work queue on a background thread. Android will also automatically stop the service when the work queue becomes empty, to help minimize the memory footprint of your application.

The SoundPoolclass, largely undocumented in Android 1.1, is now ready for widespread use in Android 1.5. The SoundPoolis designed to play back multiple overlapping sounds, particularly useful for games. Moreover, you can specify priorities for these audio streams and a maximum number of streams, so your application can simply play back clips as needed (e.g., based on game events), and Android will ensure the maximum number of streams is not exceeded. That way, you can minimize the amount of CPU power audio playback requires.

Android 1.5 also offers AudioTrack, whereby the device can play back audio that your code converts, perhaps from a streaming source, into PCM data. So, for example, should you want to implement a Voice-Over-IP (VOIP) application, you might use AudioTrackto handle playback of the audio coming off of, say, the SIP connection.

Android 1.5 also introduces the JetPlayer, designed to play back JET interactive music filesJET interactive music files.

Android 1.1 offered a MediaRecorderclass, but it would only record audio. Now, with Android 1.5, you can record video as well. You control the frame rate and size, along with the encoding (e.g., H.264) and output format (e.g., MP4). Android will then, on demand, record video off of the device’s camera to a file you specify.

http://www.icon-king.com/?p=15

http://code.google.com/android/index.html

http://www.apress.com/book/view/1430224193

http://www.apache.org/licenses/LICENSE-2.0.html

http://ant.apache.org/

http://commonsware.com/Android/

http://code.google.com/android/reference/packages.html

http://droiddraw.org/

http://windowssdk.msdn.microsoft.com/en-us/library/ms752059.aspx

http://www.adobe.com/products/flex/

http://www.mozilla.org/projects/xul/

http://www.zkoss.org/

http://www.onjava.com/pub/a/onjava/2002/09/18/relativelayout.html

http://www.ascendercorp.com/oha.html

http://moorstation.org/typoasis/designers/klein07/text01/handmade.htm

http://en.wikipedia.org/wiki/Nuvola

http://www.xmlpull.org/v1/doc/api/org/xmlpull/v1/package-summary.html

http://en.wikipedia.org/wiki/ISO_639-1

http://code.google.com/android/devel/resources-i18n.html#AlternateResources

http://www.sqlite.org

http://www.amazon.com/Definitive-Guide-SQLite/dp/1590596730

http://www.sqlite.org/different.html

https://addons.mozilla.org/en-US/firefox/addon/5817

http://www.sqlite.org/cvstrac/wiki?p=SqliteTools

http://www.sqlite.org

http://beanshell.org

http://beanshell.org/developer.html

http://hc.apache.org/

http://commonsware.com/Android/

http://openid.net/

http://oauth.net/