CustomDropdownButton class

A material design button for selecting from a custom widget.

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.

This sample shows a CustomDropdownButton with a large arrow icon, purple text style, and bold purple underline, whose value is one of "One", "Two", "Free", or "Four".

String dropdownValue = 'One';

@override
Widget build(BuildContext context) {
  return CustomDropdownButton<String>(
    value: dropdownValue,
    icon: Icon(Icons.arrow_downward),
    iconSize: 24,
    elevation: 16,
    style: TextStyle(
      color: Colors.deepPurple
    ),
    underline: Container(
      height: 2,
      color: Colors.deepPurpleAccent,
    ),
    items: <String>['One', 'Two', 'Free', 'Four']
      .map<DropdownMenuItem<String>>((String value) {
        return DropdownMenuItem<String>(
          value: value,
          child: Text(value),
        );
      })
      .toList(),
  );
}

{@end-tool}

If the onTap 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.

Requires one of its ancestors to be a Material widget.

See also:

Inheritance

Constructors

CustomDropdownButton({Key? key, String? value, String? hint, String? disabledHint, required VoidCallback onTap, int elevation = 8, TextStyle? style, Widget? underline, Widget? icon, Color? iconDisabledColor, Color? iconEnabledColor, double iconSize = 24.0, bool isDense = false, bool isExpanded = false, double itemHeight = kMinInteractiveDimension, Color? focusColor, FocusNode? focusNode, bool autofocus = false, Color? dropdownColor})
Creates a custom dropdown button.
const

Properties

autofocus → bool
True if this widget will be selected as the initial focus when no other node in its scope is currently focused.
final
disabledHint → String?
A message to show when the dropdown is disabled.
final
The background color of the dropdown.
final
elevation → int
When a DropdownMenuItem is selected, the widget that will be displayed from the list corresponds to the DropdownMenuItem of the same index in items.
final
focusColor → Color?
The color for the button's Material when it has the input focus.
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 → String?
A placeholder String that is displayed by the dropdown button.
final
icon → Widget?
The widget to use for the drop-down button's icon.
final
iconDisabledColor → Color?
The color of any Icon descendant of icon if this button is disabled, i.e. if onTap is null.
final
iconEnabledColor → Color?
The color of any Icon descendant of icon if this button is enabled, i.e. if onTap is defined.
final
iconSize → double
The size to use for the drop-down button's down arrow icon button.
final
isDense → bool
Reduce the button's height.
final
isExpanded → bool
Set the dropdown's inner contents to horizontally fill its parent.
final
itemHeight → double
If null, then the menu item heights will vary according to each menu item's intrinsic height.
final
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
onTap → VoidCallback
Called when the dropdown button is tapped.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
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 → String?
The value of the button text.
final

Methods

createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → State<CustomDropdownButton>
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