LayoutChangedNotification class

Indicates that the layout of one of the descendants of the object receiving this notification has changed in some way, and that therefore any assumptions about that layout are no longer valid.

Useful if, for instance, you're trying to align multiple descendants.

To listen for notifications in a subtree, use a NotificationListener<LayoutChangedNotification>.

To send a notification, call dispatch on the notification you wish to send. The notification will be delivered to any NotificationListener widgets with the appropriate type parameters that are ancestors of the given BuildContext.

In the widgets library, only the SizeChangedLayoutNotifier class and Scrollable classes dispatch this notification (specifically, they dispatch SizeChangedLayoutNotifications and ScrollNotifications respectively). Transitions, in particular, do not. Changing one's layout in one's build function does not cause this notification to be dispatched automatically. If an ancestor expects to be notified for any layout change, make sure you either only use widgets that never change layout, or that notify their ancestors when appropriate, or alternatively, dispatch the notifications yourself when appropriate.

Also, since this notification is sent when the layout is changed, it is only useful for paint effects that depend on the layout. If you were to use this notification to change the build, for instance, you would always be one frame behind, which would look really ugly and laggy.