changedExternalState method Null safety

  1. @protected
  2. @mustCallSuper
void changedExternalState()

Called whenever the Navigator has updated in some manner that might affect routes, to indicate that the route may wish to rebuild as well.

This is called by the Navigator whenever the NavigatorState's State.widget changes (as in State.didUpdateWidget), for example because the MaterialApp has been rebuilt. This ensures that routes that directly refer to the state of the widget that built the MaterialApp will be notified when that widget rebuilds, since it would otherwise be difficult to notify the routes that state they depend on may have changed.

It is also called whenever the Navigator's dependencies change (as in State.didChangeDependencies). This allows routes to use the Navigator's context (NavigatorState.context), for example in ModalRoute.barrierColor, and update accordingly.

The ModalRoute subclass overrides this to force the barrier overlay to rebuild.

See also:

Implementation

@protected
@mustCallSuper
void changedExternalState() { }