Tasks in Android

Question

I am trying to understand conceptually what a task is in Android. So is it correct that a task can have multiple activities and can run one activity at a time? But is a task like a unix process? And each activity can be thought of as a thread within the process? Looking to clarify my somewhat weak understanding.

Answer 1

A task, unlike a Unix process, is basically an UI concept.

From the documentation - Tasks and Back Stacks

A task is a collection of activities that users interact with when performing a certain job. The activities are arranged in a stack (the "back stack"), in the order in which each activity is opened.

The activities that make up a task can belong to different applications (and hence, to different processes). That's why inter-activity communication in Android is done via Intents (basically, messaging objects than can be serialized) and not via direct method calls -- even when the called activity is part of the same application as the caller.

A user can switch freely between tasks (with the "Recents" button) but cannot move arbitrarily between the activities that make up a task. Normally they can only go one step back, via the "Back" button.

You should take a look at the documentation -- it's quite well explained there.

An Android application maps to a Unix process (more or less, since an app can run more than one process if it so desires) . But there is not a one-to-one mapping with tasks -- a task can contain activities from multiple applications, and a single application can have activities in multiple tasks.