Task and backstack

Task and Back Stack Deep Dive¶

Overview¶

A task is a collection of activities arranged in a back stack. Back navigation pops activities in LIFO order and task/intent flags can significantly change behavior.

Core Concepts¶

Task: logical user journey container.
Back stack: activity stack inside task.
Recents screen: task-level entry point.

Launch and Back Behavior¶

New activity usually pushed to current task stack.
Back pops top activity.
If root popped, task leaves foreground.

Important Flags¶

FLAG_ACTIVITY_NEW_TASK: launch in new or existing task by affinity.
FLAG_ACTIVITY_CLEAR_TOP: pop above target if already in stack.
FLAG_ACTIVITY_SINGLE_TOP: reuse top instance via onNewIntent().

Launch Modes (high level)¶

standard
singleTop
singleTask
singleInstance / singleInstancePerTask

Use sparingly; prefer Navigation Component defaults unless specific behavior needed.

Interview Traps¶

Mixing launch modes and flags can create unexpected UX.
Deep links may create parallel task flows if misconfigured.

Key Takeaways¶

Understand default stack behavior first, then add flags intentionally.
Validate navigation with real back/recents testing.