What is a Task and in what cases is it used?

A Task is a unit of work in Android, representing a collection of Activities that are related to each other. Activities within a single Task are arranged in a stack (back stack) in the order they were opened.

Used for:

• Managing the Activity lifecycle: A Task determines the visibility and accessibility of Activities.
• Navigation between applications: When launching an Activity from another app, it is usually placed in its own Task.
• Defining the behavior of the "Back" button: The "Back" button sequentially closes Activities in the current Task.
• Isolation of Activities: Activities from different Tasks do not interact directly by default.

Examples of usage:

• Normal app usage: Opening different screens (Activities) within a single Task.
• Launching a gallery from a messenger: The gallery opens in its own Task, and after selecting an image, it returns to the messenger's Task.
• Handling notifications: Opening an Activity from a notification can create a new Task or use an existing one, depending on the intent flags.

Special behavior of a Task:

• Each Task can have only one root Activity.
• A new Task is created when an Activity is launched with the FLAG_ACTIVITY_NEW_TASK flag.
• An existing Task can be brought to the foreground if an Activity that is already part of it is called with the FLAG_ACTIVITY_SINGLE_TOP or FLAG_ACTIVITY_CLEAR_TOP flags.

// Example of launching an Activity in a new Task
val intent = Intent(this, NewTaskActivity::class.java)
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
startActivity(intent)