GlobalKey<T extends State<StatefulComponent> > class
A key that is unique across the entire app.
Global keys uniquely identify elements. Global keys provide access to other objects that are associated with those elements, such as BuildContext. For StatefulComponents, global keys also provide access to State.
Components that have global keys reparent their subtrees when they are moved from one location in the tree to another location in the tree. In order to reparent its subtree, a component must arrive at its new location in the tree in the same animation frame in which it was removed from its old location in the tree.
Reparenting an Element using a global key is relatively expensive, as this operation will trigger a call to State.deactivate on the associated State and all of its descendants; then force all components that depends on an InheritedComponent to rebuild.
If you don't need any of the features listed above, consider using a Key, ValueKey, or UniqueKey instead.
You cannot simultaneously include two components in the tree with the same global key. Attempting to do so will assert at runtime.
Pitfalls
GlobalKeys should not be re-created on every build. They should usually be long-lived objects owned by a State object, for example.
Creating a new GlobalKey on every build will throw away the state of the subtree associated with the old key and create a new fresh subtree for the new key. Besides harming performance, this can also cause unexpected behavior in components in the subtree.
Instead, a good practice is to let a State object own the GlobalKey, and instantiate it outside the build method, such as in State.initState.
See also:
- The discussion at Component.key for more information about how components use keys.
- Inheritance
- Implementers
- Annotations
Constructors
- GlobalKey()
-
Creates a global key.
const
Properties
- currentComponent → Component?
-
The component in the tree that currently has this global key.
no setter
- currentContext → BuildContext?
-
The build context in which the component with this key builds.
no setter
- currentState → T?
-
The State for the component in the tree that currently has this global key.
no setter
- hashCode → int
-
The hash code for this object.
no setterinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
toString(
) → String -
A string representation of this object.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited