Combobox<T> class
A material design button for selecting from a list of items.
A combobox 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.
The type T
is the type of the value that each combobox item represents.
All the entries in a given menu must represent values with consistent types.
Typically, an enum is used. Each ComboboxItem in items must be
specialized with that same type argument.
The onChanged callback should update a state variable that defines the combobox's value. It should also call State.setState to rebuild the combobox with the new value.
{@tool dartpad --template=stateful_widget_scaffold_center}
This sample shows a Combobox
with a large arrow icon,
purple text style, and bold purple underline, whose value is one of "One",
"Two", "Free", or "Four".
String comboboxValue = 'One';
@override
Widget build(BuildContext context) {
return Combobox<String>(
value: comboboxValue,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: TextStyle(
color: Colors.deepPurple
),
onChanged: (String? newValue) {
setState(() {
comboboxValue = newValue!;
});
},
items: <String>['One', 'Two', 'Free', 'Four']
.map<ComboboxItem<String>>((String value) {
return ComboboxItem<String>(
value: value,
child: Text(value),
);
})
.toList(),
);
}
{@end-tool}
If the onChanged callback is null or the list of items is null then the combobox 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 placeholder is non-null, the placeholder widget will instead be displayed.
Requires one of its ancestors to be a Material widget.
See also:
- ComboboxItem, the class used to represent the items.
- ElevatedButton, TextButton, ordinary buttons that trigger a single action.
- material.io/design/components/menus.html#combobox-menu
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- Combobox
Constructors
-
Combobox({Key? key, required List<
ComboboxItem< ? items, ComboboxBuilder? selectedItemBuilder, T? value, Widget? placeholder, Widget? disabledHint, ValueChanged<T> >T?> ? onChanged, VoidCallback? onTap, int elevation = 8, TextStyle? style, Widget? icon, Color? iconDisabledColor, Color? iconEnabledColor, double iconSize = 24.0, bool isExpanded = false, double? itemHeight = kMinInteractiveDimension, Color? focusColor, FocusNode? focusNode, bool autofocus = false, Color? comboboxColor}) - Creates a combobox button.
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
- comboboxColor → Color?
-
The background color of the combobox.
final
- disabledHint → Widget?
-
A preferred placeholder widget that is displayed when the combobox is disabled.
final
- elevation → int
-
The z-coordinate at which to place the menu when open.
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
- 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 onChanged is null.
final
- iconEnabledColor → Color?
-
The color of any Icon descendant of icon if this button is enabled,
i.e. if onChanged is defined.
final
- iconSize → double
-
The size to use for the drop-down button's down arrow icon button.
final
- isExpanded → bool
-
Set the combobox'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
-
items
→ List<
ComboboxItem< ?T> > -
The list of items the user can select.
final
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
-
onChanged
→ ValueChanged<
T?> ? -
Called when the user selects an item.
final
- onTap → VoidCallback?
-
Called when the combobox button is tapped.
final
- placeholder → Widget?
-
A placeholder widget that is displayed by the combobox button.
final
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
- selectedItemBuilder → ComboboxBuilder?
-
A builder to customize the combobox buttons corresponding to the
ComboboxItems in items.
final
- style → TextStyle?
-
The text style to use for text in the combobox button and the combobox
menu that appears when you tap the button.
final
- value → T?
-
The value of the currently selected ComboboxItem.
final
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → _ComboboxState< 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