FocusScope class

A FocusScope is similar to a Focus, but also serves as a scope for other Focuss and FocusScopes, grouping them together.

Like Focus, FocusScope provides an onFocusChange as a way to be notified when the focus is given to or removed from this widget.

The onKey argument allows specification of a key event handler that is invoked when this node or one of its children has focus. Keys are handed to the primary focused widget first, and then they propagate through the ancestors of that node, stopping if one of them returns true from onKey, indicating that it has handled the event.

A FocusScope manages a FocusScopeNode. Managing a FocusScopeNode means managing its lifecycle, listening for changes in focus, and re-parenting it when the widget hierarchy changes. See FocusNode and FocusScopeNode for more information about the details of what node management entails if not using a FocusScope widget.

A DefaultTraversalPolicy widget provides the FocusTraversalPolicy for the FocusScopeNodes owned by its descendant widgets. Each FocusScopeNode has FocusNode descendants. The traversal policy defines what "previous focus", "next focus", and "move focus in this direction" means for them.

FocusScopeNodes remember the last FocusNode that was focused within their descendants, and can move that focus to the next/previous node, or a node in a particular direction when the FocusNode.nextFocus, FocusNode.previousFocus, or FocusNode.focusInDirection are called on a FocusNode or FocusScopeNode.

To move the focus, use methods on FocusScopeNode. For instance, to move the focus to the next node, call Focus.of(context).nextFocus().

See also:

  • FocusScopeNode, which represents a scope node in the focus hierarchy.
  • FocusNode, which represents a node in the focus hierarchy and has an explanation of the focus system.
  • Focus, a widget that manages a FocusNode and allows easy access to managing focus without having to manage the node.
  • FocusManager, a singleton that manages the focus and distributes key events to focused nodes.
  • FocusTraversalPolicy, an object used to determine how to move the focus to other nodes.
  • DefaultFocusTraversal, a widget used to configure the default focus traversal policy for a widget subtree.
Inheritance

Constructors

FocusScope({Key key, FocusScopeNode node, @required Widget child, bool autofocus: false, ValueChanged<bool> onFocusChange, FocusOnKeyCallback onKey, String debugLabel })
Creates a widget that manages a FocusScopeNode. [...]
const

Properties

autofocus bool
{@template flutter.widgets.Focus.autofocus} True if this widget will be selected as the initial focus when no other node in its scope is currently focused. [...]
final, inherited
canRequestFocus bool
If true, this widget may request the primary focus. [...]
final, inherited
child Widget
The child widget of this Focus. [...]
final, inherited
debugLabel String
A debug label for this widget. [...]
final, inherited
focusNode FocusNode
{@template flutter.widgets.Focus.focusNode} An optional focus node to use as the focus node for this widget. [...]
final, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
key Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited
onFocusChange ValueChanged<bool>
Handler called when the focus changes. [...]
final, inherited
onKey FocusOnKeyCallback
Handler for keys pressed when this object or one of its children has focus. [...]
final, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
skipTraversal bool
Sets the FocusNode.skipTraversal flag on the focus node so that it won't be visited by the FocusTraversalPolicy. [...]
final, inherited

Methods

createState() → _FocusScopeState
Creates the mutable state for this widget at a given location in the tree. [...]
override
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
toDiagnosticsNode({String name, DiagnosticsTreeStyle style }) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) String
Returns a string representation of this object.
inherited
toStringDeep({String prefixLineOne: '', String prefixOtherLines, DiagnosticLevel minLevel: DiagnosticLevel.debug }) String
Returns a string representation of this node and its descendants. [...]
inherited
toStringShallow({String joiner: ', ', DiagnosticLevel minLevel: DiagnosticLevel.debug }) String
Returns a one-line detailed description of the object. [...]
inherited
toStringShort() String
A short, textual description of this widget.
inherited

Operators

operator ==(dynamic other) bool
The equality operator. [...]
inherited

Static Methods

of(BuildContext context) FocusScopeNode
Returns the FocusScopeNode of the FocusScope that most tightly encloses the given context. [...]
override