Android™ Concurrency

5. Looper/Handler

The ants go marching one by one. Hurrah! Hurrah!

Children’s song

Although AsyncTasks are the first concurrency construct that most developers encounter when they start working with Android, they are not its central concurrency construct. The basic concurrency construct in Android is the Looper/Handler.

Introducing the Looper/Handler

The Looper/Handler framework, like several other important parts of Android’s internal architecture, was probably inspired by the BeOS operating system—in particular, its BLooper and BHandler classes.

The Looper framework is an extension of the safe publication idiom, introduced Chapter 2, “Java Concurrency,” and shown again in Figure 5.1. The idiom consists of a drop box and a lock on that drop ...