DropdownButton2<T> class
A Material Design button for selecting from a list of items.
A dropdown button lets the user select from a number of items. The button shows the currently selected item as well as an arrow that opens a menu for selecting another item.
One ancestor must be a Material widget and typically this is provided by the app's Scaffold.
The type T is the type of the value that each dropdown item represents.
All the entries in a given menu must represent values with consistent types.
Typically, an enum is used. Each DropdownMenuItem in items must be
specialized with that same type argument.
The onChanged callback should update a state variable that defines the dropdown's value. It should also call State.setState to rebuild the dropdown with the new value.
If the onChanged callback is null or the list of items is null then the dropdown button will be disabled, i.e. its arrow will be displayed in grey and it will not respond to input. A disabled button will display the disabledHint widget if it is non-null. However, if disabledHint is null and hint is non-null, the hint widget will instead be displayed.
See also:
- DropdownButtonFormField2, which integrates with the Form widget.
- DropdownMenuItem, the class used to represent the items.
- DropdownButtonHideUnderline, which prevents its descendant dropdown buttons from displaying their underlines.
- ElevatedButton, TextButton, ordinary buttons that trigger a single action.
- material.io/design/components/menus.html#dropdown-menu
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- DropdownButton2
Constructors
-
DropdownButton2({Key? key, required List<
DropdownMenuItem< ? items, DropdownButtonBuilder? selectedItemBuilder, T? value, Widget? hint, Widget? disabledHint, ValueChanged<T> >T?> ? onChanged, OnMenuStateChangeFn? onMenuStateChange, TextStyle? style, Widget? underline, bool isDense = false, bool isExpanded = false, FocusNode? focusNode, bool autofocus = false, bool? enableFeedback, AlignmentGeometry alignment = AlignmentDirectional.centerStart, ButtonStyleData? buttonStyleData, IconStyleData iconStyleData = const IconStyleData(), DropdownStyleData dropdownStyleData = const DropdownStyleData(), DropdownSearchData<T> ? dropdownSearchData, Widget? customButton, bool openWithLongPress = false, bool barrierDismissible = true, Color? barrierColor, String? barrierLabel}) - Creates a DropdownButton2. It's customizable DropdownButton with steady dropdown menu and many other features.
Properties
- alignment → AlignmentGeometry
-
Defines how the hint or the selected item is positioned within the button.
final
- autofocus → bool
-
True if this widget will be selected as the initial focus when no other
node in its scope is currently focused.
final
- barrierColor → Color?
-
The color to use for the modal barrier. If this is null, the barrier will
be transparent.
final
- barrierDismissible → bool
-
Whether you can dismiss this route by tapping the modal barrier.
final
- barrierLabel → String?
-
The semantic label used for a dismissible barrier.
final
-
Used to configure the theme of the button
final
- customButton → Widget?
-
Uses custom widget like icon,image,etc.. instead of the default button
final
- disabledHint → Widget?
-
A preferred placeholder widget that is displayed when the dropdown is disabled.
final
-
dropdownSearchData
→ DropdownSearchData<
T> ? -
Used to configure searchable dropdowns
final
- dropdownStyleData → DropdownStyleData
-
Used to configure the theme of the dropdown menu
final
- enableFeedback → bool?
-
Whether detected gestures should provide acoustic and/or haptic feedback.
final
- focusNode → FocusNode?
-
An optional focus node to use as the focus node for this widget.
final
- hashCode → int
-
The hash code for this object.
no setterinherited
- hint → Widget?
-
A placeholder widget that is displayed by the dropdown button.
final
- iconStyleData → IconStyleData
-
Used to configure the theme of the button's icon
final
- isDense → bool
-
Reduce the button's height.
final
- isExpanded → bool
-
Set the dropdown's inner contents to horizontally fill its parent.
final
-
items
→ List<
DropdownMenuItem< ?T> > -
The list of items the user can select.
final
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
-
Used to configure the theme of the dropdown menu items
final
-
onChanged
→ ValueChanged<
T?> ? -
Called when the user selects an item.
final
- onMenuStateChange → OnMenuStateChangeFn?
-
Called when the dropdown menu opens or closes.
final
- openWithLongPress → bool
-
Opens the dropdown menu on long-pressing instead of tapping
final
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
- selectedItemBuilder → DropdownButtonBuilder?
-
A builder to customize the dropdown buttons corresponding to the
DropdownMenuItems in items.
final
- style → TextStyle?
-
The text style to use for text in the dropdown button and the dropdown
menu that appears when you tap the button.
final
- underline → Widget?
-
The widget to use for drawing the drop-down button's underline.
final
- value → T?
-
The value of the currently selected DropdownMenuItem.
final
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → State< DropdownButton2< T> > -
Creates the mutable state for this widget at a given location in the tree.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of
DiagnosticsNodeobjects 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