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<T>>? items, DropdownButtonBuilder? selectedItemBuilder, T? value, Widget? hint, Widget? disabledHint, ValueChanged<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(), MenuItemStyleData menuItemStyleData = const MenuItemStyleData(), 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

buttonStyleData → ButtonStyleData?

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 setter, inherited

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.

final, inherited

menuItemStyleData → MenuItemStyleData

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 setter, inherited

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 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