uidropdown
Create drop-down component
Description
creates a drop-down in a
new figure window and returns the dd
= uidropdownDropDown
object.
MATLAB® calls the uifigure
function to create the
figure.
specifies object properties using one or more dd
= uidropdown(___,Name,Value
)Name,Value
pair
arguments. Use this option with any of the input argument combinations in the
previous syntaxes. Use the Name,Value
pair,
Editable,'on'
to specify a drop-down component that allows
the app user to type text into the drop-down component or select a predefined
option.
Examples
Create Drop-Down Component
Create a drop-down component with the default items.
fig = uifigure; dd = uidropdown(fig);
Clicking anywhere in the drop-down component causes it to open.
Set and Access Drop Down Properties
Create a drop-down component and specify the options.
fig = uifigure; dd = uidropdown(fig,'Items',{'Red','Yellow','Blue','Green'},... 'Value','Blue');
Determine the value associated with the selected option.
value = dd.Value
value = 'Blue'
By default, the ItemsData
property is empty, so the
drop-down component value corresponds to the element selected in the
drop-down component.
Associate data values with each drop-down component item.
dd.ItemsData = [1 2 3 4];
Determine the value associated with the selected option.
value = dd.Value
value = 3
Notice that when the ItemsData
property value is not
empty, the value of the drop-down component is the
ItemsData
value that corresponds to the selected
Items
value element.
Create an Editable Drop Down
fig = uifigure; dd = uidropdown(fig,'Editable','on');
Clicking anywhere in the drop-down component, other than the down-arrow, inserts a cursor, enabling the user to type text in the drop-down component.
Code Response to Drop Down Selection
Create a plot and a drop-down component. When the app user makes a selection from the drop-down component, the plot changes color.
Save the following code to plotOptions.m
on your
MATLAB path. This code creates a window containing a plot and a
drop-down component. When an app user changes the drop-down component
selection, the ValueChangedFcn
callback changes the
plot color.
function plotOptions fig = uifigure; fig.Position(3:4) = [440 320]; ax = uiaxes('Parent',fig,... 'Position',[10 10 300 300]); x = linspace(-2*pi,2*pi); y = sin(x); p = plot(ax,x,y); p.Color = 'Blue'; dd = uidropdown(fig,... 'Position',[320 160 100 22],... 'Items',{'Red','Yellow','Blue','Green'},... 'Value','Blue',... 'ValueChangedFcn',@(dd,event) selection(dd,p)); end % Create ValueChangedFcn callback: function selection(dd,p) val = dd.Value; p.Color = val; end
Run plotOptions
. Select green from
the drop-down component to change the plot color to green.
Code Response to Drop-Down Component Entry or Selection
Create a drop-down component and a lamp. When the app user makes a selection from the drop-down component, the lamp size changes.
Save the following code to a lampSize.m
on your
MATLAB path. This code creates a figure window containing a drop-down
component and a lamp. When an app user changes the drop-down component
selection, the ValueChangedFcn
callback changes the
size of the lamp.
function lampSize % Create figure and components fig = uifigure('Position',[100 100 300 275]); lmp = uilamp(fig,... 'Position',[100 30 20 20]); dd = uidropdown(fig,... 'Editable','on',... 'Position',[84 204 100 20],... 'Items',{'Size x 1','Size x 2','Size x 3','Size x 4'},... 'ItemsData',[1 2 3 4],... 'Value',1,... 'ValueChangedFcn',@(dd,event) optionSelected(dd,lmp)); end % Create ValueChangedFcn callback function optionSelected(dd,lmp) val = dd.Value; s = [20 20]; switch val case {1, 2, 3, 4} % User selected a defined option size = val * s; lmp.Position(3:4) = size; otherwise % User typed a value m = str2num(val); size = m * s; lmp.Position(3:4) = size; end end
Run lampSize
and select various options from the
drop-down component.
Type a value in the drop-down component and press Enter. The lamp size changes. (If you type a large value, you might have to resize the figure to see the lamp.)
Input Arguments
parent
— Parent container
Figure
object (default) | Panel
object | Tab
object | ButtonGroup
object | GridLayout
object
Parent container, specified as a Figure
object created using
the uifigure
function, or one of its child
containers: Tab
, Panel
, ButtonGroup
, or GridLayout
. If you do not specify a parent container,
MATLAB calls the uifigure
function to create a new Figure
object that serves as the parent container.
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: 'Items',{'Red','Yellow','Blue'}
specifies the options
presented in the drop-down component.
The properties listed here are a subset of the available properties. For the full list, see DropDown Properties.
Value
— Value
element of Items
| element of ItemsData
Value, specified as an element of the Items
or
ItemsData
arrays. By default, Value
is the
first element in Items
.
Specifying Value
as an element of Items
selects the drop-down item that matches that element. If ItemsData
is not empty, then Value
must be set to an element of
ItemsData
, and the drop-down will select the associated item in
the list.
When Editable
is set to 'on'
, you can
additionally specify Value
as a character vector or string
scalar.
Items
— Drop-down items
{'Option 1','Option 2','Option 3','Option
4'}
(default) | cell array of character vectors | string array | ...
Drop-down items, specified as a cell array of character vectors, string array, or 1-D
categorical array. Duplicate elements are allowed. The drop-down component displays as
many options as there are elements in the Items
array. If you
specify this property as a categorical array, MATLAB uses the values in the array, not the full set of categories.
Example: {'Red','Yellow','Blue'}
Example: {'1','2','3'}
ItemsData
— Data associated with each element of the Items
property value
empty array ([]
) (default) | 1-by-n numeric array | 1-by-n cell array
Data associated with each element of the Items
property
value, specified as a 1-by-n numeric array or a 1-by-n cell array.
Duplicate elements are allowed.
For example, if you set the Items
value
to employee names, you might set the ItemsData
value
to corresponding employee ID numbers. The ItemsData
value
is not visible to the app user.
If the number of array elements in the ItemsData
value
and the Items
value do not match, one of the
following occurs:
When the
ItemsData
value is empty, then all the elements of theItems
value are presented to the app user.When the
ItemsData
value has more elements than theItems
value, then all the elements of theItems
value are presented to the app user. MATLAB ignores the extraItemsData
elements.When the
ItemsData
value is not empty, but has fewer elements than theItems
value, the only elements of theItems
value presented to the app user are those that have a corresponding element in theItemsData
value.
Example: {'One','Two','Three'}
Example: [10 20 30 40]
Editable
— Editable state of drop-down component
'off'
(default) | on/off logical value
Editable state of the drop-down component, specified as 'off'
or
'on'
, or as numeric or logical 1
(true
) or 0
(false
). A
value of 'on'
is equivalent to true
, and
'off'
is equivalent to false
. Thus, you can
use the value of this property as a logical value. The value is stored as an on/off
logical value of type matlab.lang.OnOffSwitchState
.
If the Enable
property value is 'off'
,
then the app user cannot change the drop-down component text, even
if the Editable property value is 'on'
.
ValueChangedFcn
— Value changed callback
''
(default) | function handle | cell array | character vector
Value changed callback, specified as one of these values:
A function handle.
A cell array in which the first element is a function handle. Subsequent elements in the cell array are the arguments to pass to the callback function.
A character vector containing a valid MATLAB expression (not recommended). MATLAB evaluates this expression in the base workspace.
This callback function executes when the user selects a different option from the
drop-down list. It does not execute if the Value
property changes
programmatically.
This callback function can access specific information about the user’s interaction
with the drop-down. MATLAB passes this information in a ValueChangedData
object as the second argument to your callback function.
In App Designer, the argument is called event
. You can query the
object properties using dot notation. For example,
event.PreviousValue
returns the previous value of the drop-down.
The ValueChangedData
object is not available to
callback functions specified as character vectors.
The following table lists the properties of the ValueChangedData
object.
Property | Value |
---|---|
Value | Drop-down component value after app user’s most recent interaction with it. |
PreviousValue | Drop-down component value before app user’s most recent interaction with it. |
Edited | Logical value that indicates whether the callback was executed as a result of typing a new value into the drop-down component.
|
Source | Component that executes the callback. |
EventName | 'ValueChanged' |
For more information about writing callbacks, see Callbacks in App Designer.
DropDownOpeningFcn
— Drop-down menu opening callback
''
(default) | function handle | cell array | character vector
Drop-down menu opening callback, specified as one of these values:
A function handle.
A cell array in which the first element is a function handle. Subsequent elements in the cell array are the arguments to pass to the callback function.
A character vector containing a valid MATLAB expression (not recommended). MATLAB evaluates this expression in the base workspace.
This property specifies a callback function to execute when the user clicks to open the drop-down menu. A possible use for this callback is to dynamically update the list of entries in the drop-down menu.
This callback function can access specific information about the user’s interaction
with the drop-down. MATLAB passes this information in a DropDownOpeningData
object as the second argument to your callback
function. In App Designer, the argument is called event
. You can
query the object properties using dot notation. For example,
event.Source
returns the DropDown
object that
the user interacts with to trigger the callback. The DropDownOpeningData
object is not available to callback functions
specified as character vectors.
The following table lists the properties of the DropDownOpeningData
object.
Property | Value |
---|---|
Source | Component that executes the callback |
EventName | 'DropDownOpening' |
For more information about writing callbacks, see Callbacks in App Designer.
Position
— Location and size of drop-down component
[100 100 100 22]
(default) | [left bottom width height]
Location and size of the drop-down component relative to the
parent, specified as the vector [left bottom width height]
.
This table describes each element in the vector.
Element | Description |
---|---|
left | Distance from the inner left edge of the parent container to the outer left edge of the drop-down component |
bottom | Distance from the inner bottom edge of the parent container to the outer bottom edge of the drop-down component |
width | Distance between the right and left outer edges of the drop-down component |
height | Distance between the top and bottom outer edges of the drop-down component |
All measurements are in pixel units.
The Position
values are relative to the
drawable area of the parent container. The drawable area is the area
inside the borders of the container and does not include the area occupied by decorations such
as a menu bar or title.
Example: [100 100 100 22]
Version History
Introduced in R2016aR2022b: Program a response to a user clicking the drop-down component
Use the ClickedFcn
callback property to program a response to a
user clicking the drop-down component.
For more information, see DropDown Properties.
R2021a: Specify placeholder text
Provide a short hint that describes the expected drop-down component input by
using the Placeholder
property.
For more information, see DropDown Properties.
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