The OverlaySupportEntry associated with TransientKey will be dismiss immediately
when next OverlaySupportEntry showing by showOverlay with the same key.
This key was designed for toast, but it seems wired, so have not use yet.
final key = const TransientKey('transient');
showSimpleNotification(Text('modal example'), key: modalKey);
// The previous notification will be dismiss immediately, instead of have
// a disappearing animation effect.
showSimpleNotification(Text('modal example 2'), key: modalKey);
The hash code for this object. [...]
A representation of the runtime type of the object.
The value to which this key delegates its operator==
Invoked when a non-existent method or property is accessed. [...]
Returns a string representation of this object.