Android Service

"A service runs in the main thread of its hosting process—the service does not create its own thread and does not run in a separate process (unless you specify otherwise). This means that, if your service is going to do any CPU intensive work or blocking operations (such as MP3 playback or networking), you should create a new thread within the service to do that work. By using a separate thread, you will reduce the risk of Application Not Responding (ANR) errors and the application's main thread can remain dedicated to user interaction with your activities."

"you can ensure that your service is private to your application only if you include theandroid:exported attribute and set it to "false". This is effective even if your service supplies intent filters"

"If you're building an application for Android 1.6 or lower, you need to implement onStart(), instead of onStartCommand() (in Android 2.0, onStart() was deprecated in favor of onStartCommand())."

"IntentService: If you decide to also override other callback methods, such as onCreate(), onStartCommand(), or onDestroy(), be sure to call the super implementation, so that the IntentService can properly handle the life of the worker thread."

"A foreground service is a service that's considered to be something the user is actively aware of and thus not a candidate for the system to kill when low on memory. A foreground service must provide a notification for the status bar, which is placed under the "Ongoing" heading, which means that the notification cannot be dismissed unless the service is either stopped or removed from the foreground."