- A
Key
is an identifier for Widgets
, Elements
and SemanticsNodes
.
- A new widget will only be used to update an existing element if its key is the same as the key of the current widget associated with the element.
- Keys must be unique amongst the Elements with the same parent.
- Subclasses of
Key
should either subclass LocalKey
or GlobalKey
.
- Keys are useful when manipulating collections of widgets of the same type.
- If you find yourself adding, removing, or reordering a collection of widgets of the same type that hold some state, then, you should use a key.