In what cases is the deactivate function activated in the system?

In Flutter, the deactivate function is called when a widget is removed from the widget tree but not yet permanently destroyed. This occurs, for example, when a widget is temporarily removed from the tree due to a rebuild or move, but can be re-added later. The deactivate method allows you to perform actions when the widget is "deactivated," such as releasing resources or canceling subscriptions, without fully destroying the state.

Example: if you have a StatefulWidget and it rebuilds with a change in structure, deactivate will be called before the widget is removed from the tree.