Каким образом ActivityManager определяет, когда нужно инициировать вызов метода onResume для активной Activity?

The ActivityManager in Android manages the lifecycle of an Activity and calls the onResume method when the Activity should become active and interact with the user.

This occurs when:

• The Activity becomes visible and is on the foreground.
• Other Activities that were covering it are closed or moved to the background.

The ActivityManager tracks the stack of Activities and their states. When the current Activity transitions to the "Resumed" state, the system calls onResume so that the Activity can start interacting with the user, resume animations, input processing, etc.

For example, onResume is called when launching an Activity or returning to it from another Activity.