Overlay class
A stack of entries that can be managed independently.
Overlays let independent child widgets "float" visual elements on top of other widgets by inserting them into the overlay's stack. The overlay lets each of these widgets manage their participation in the overlay using OverlayEntry objects.
Although you can create an Overlay directly, it's most common to use the overlay created by the Navigator in a WidgetsApp, CupertinoApp or a MaterialApp. The navigator uses its overlay to manage the visual appearance of its routes.
The Overlay widget uses a custom stack implementation, which is very similar to the Stack widget. The main use case of Overlay is related to navigation and being able to insert widgets on top of the pages in an app. For layout purposes unrelated to navigation, consider using Stack instead.
An Overlay widget requires a Directionality widget to be in scope, so that it can resolve direction-sensitive coordinates of any Positioned.directional children.
For widgets drawn in an OverlayEntry, do not assume that the size of the Overlay is the size returned by MediaQuery.sizeOf. Nested overlays can have different sizes.
To create a local project with this code sample, run:
flutter create --sample=widgets.Overlay.1 mysample
See also:
- OverlayEntry, the class that is used for describing the overlay entries.
- OverlayState, which is used to insert the entries into the overlay.
- WidgetsApp, which inserts an Overlay widget indirectly via its Navigator.
- MaterialApp, which inserts an Overlay widget indirectly via its Navigator.
- CupertinoApp, which inserts an Overlay widget indirectly via its Navigator.
- Stack, which allows directly displaying a stack of widgets.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- Overlay
Constructors
-
Overlay({Key? key, List<
OverlayEntry> initialEntries = const <OverlayEntry>[], Clip clipBehavior = Clip.hardEdge}) -
Creates an overlay.
const
Properties
- clipBehavior → Clip
-
The content will be clipped (or not) according to this option.
final
- hashCode → int
-
The hash code for this object.
no setterinherited
-
initialEntries
→ List<
OverlayEntry> -
The entries to include in the overlay initially.
final
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → OverlayState -
Creates the mutable state for this widget at a given location in the tree.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of DiagnosticsNode objects describing this node's
children.
inherited
-
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
inherited
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent 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.info}) → String -
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 ==(
Object other) → bool -
The equality operator.
inherited
Static Methods
-
maybeOf(
BuildContext context, {bool rootOverlay = false}) → OverlayState? - The OverlayState from the closest instance of Overlay that encloses the given context within the closest LookupBoundary, if any.
-
of(
BuildContext context, {bool rootOverlay = false, Widget? debugRequiredFor}) → OverlayState - The OverlayState from the closest instance of Overlay that encloses the given context within the closest LookupBoundary, and, in debug mode, will throw if one is not found.
-
wrap(
{Key? key, Clip clipBehavior = Clip.hardEdge, required Widget child}) → Widget -
Wrap the provided
childin an Overlay to allow other visual elements (packed in OverlayEntrys) to float on top of the child.