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.

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'}

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:

Example: {'One','Two','Three'}

Example: [10 20 30 40]

Index of the component value in the list of items or item data, specified as a positive integer.

In most cases, you can use the Value property to query and update the component value. However, the ValueIndex property can be useful when both the Items and ItemsData properties are nonempty. In this case, you can use the ValueIndex property to query the element of Items that corresponds to the current value.

fig = uifigure;
dd = uidropdown(fig, ...
    "Items",["Red","Green","Blue"], ...
    "ItemsData",["#F00","#0F0","#00F"]);
idx = dd.ValueIndex;
 
disp(dd.Items(idx) + ": " + dd.Value)

Red: #F00

Placeholder text, specified as a character vector or string scalar. The placeholder provides a short description of the drop-down items. The placeholder text appears only when the drop-down component displays ''. There are two situations where this happens:

For example, to display a placeholder in a drop-down component with no ItemsData, add '' to Items and set the Value property to '':

fig = uifigure('Position',[100 100 300 200]);
dd = uidropdown(fig,'Items',{'','One','Two'}, ...
                'Value','', ...
                'Placeholder','Options');

Font name, specified as a system supported font name. The default font depends on the specific operating system and locale.

If the specified font is not available, then MATLAB uses the best match among the fonts available on the system where the app is running.

Example: 'Arial'

Font size, specified as a positive number. The units of measurement are pixels. The default font size depends on the specific operating system and locale.

Example: 14

Font weight, specified as one of these values:

Not all fonts have a bold font weight. For fonts that do not, specifying 'bold' results in the normal font weight.

Font angle, specified as 'normal' or 'italic'. Not all fonts have an italic font angle. For fonts that do not, specifying 'italic' results in the normal font angle.

Font color, specified as an RGB triplet, a hexadecimal color code, or one of the options listed in the table.

RGB triplets and hexadecimal color codes are useful for specifying custom colors.

Alternatively, you can specify some common colors by name. This table lists the named color options, the equivalent RGB triplets, and hexadecimal color codes.

Here are the RGB triplets and hexadecimal color codes for the default colors MATLAB uses in many types of plots.

Background color, specified as an RGB triplet, a hexadecimal color code, or one of the color options listed in the table.

RGB triplets and hexadecimal color codes are useful for specifying custom colors.

Alternatively, you can specify some common colors by name. This table lists the named color options, the equivalent RGB triplets, and hexadecimal color codes.

Here are the RGB triplets and hexadecimal color codes for the default colors MATLAB uses in many types of plots.

This property is read-only.

Configuration of added styles created using the uistyle function, returned as an n-by-3 table array. Each row of the table array corresponds to a style that is currently applied to the drop-down component. Styles that are added consecutively are given a style order number of n+1. The Target and TargetIndex columns specify the part of the component that the style was added to. The Style column specifies the style class name.

Use this property if you want to remove a style from the drop-down component using the removeStyle function.

Example: Remove a Style

First, add two styles to a drop-down component.

fig = uifigure;
fig.Position = [100 100 300 250];
dd = uidropdown(fig);

s1 = uistyle("FontColor","blue");
s2 = uistyle("FontColor","red");

addStyle(dd,s1,"item",1);
addStyle(dd,s2,"item",[2 3 4]);

When you query dd.StyleConfigurations, MATLAB returns a 2-by-3 table array. The blue font style was added to the component first, so it is style order number 1. The TargetIndex value for the level style, {[1]}, indicates that the style was applied to the first item in the component. Similarly, the second style was added to the last three items in the component

dd.StyleConfigurations

ans =

  2×3 table

         Target    TargetIndex              Style          
         ______    ___________    _________________________

    1     item      {[    1]}     1×1 matlab.ui.style.Style
    2     item      {[2 3 4]}     1×1 matlab.ui.style.Style

Remove the second style that was added to the drop-down component by specifying style order number 2. The component appearance updates to use only the first style.

removeStyle(dd,2)

State of visibility, specified as 'on' or 'off', 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.

To make your app start faster, set the Visible property to 'off' for all UI components that do not need to appear at startup.

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'.

Operational state, specified as 'on' or 'off', 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.

Tooltip, specified as a character vector, cell array of character vectors, string array, or 1-D categorical array. Use this property to display a message when the user hovers the pointer over the component at run time. The tooltip displays even when the component is disabled. To display multiple lines of text, specify a cell array of character vectors or a string array. Each element in the array becomes a separate line of text. If you specify this property as a categorical array, MATLAB uses the values in the array, not the full set of categories.

Context menu, specified as a ContextMenu object created using the uicontextmenu function. Use this property to display a context menu when you right-click on a component.

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.

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]

Inner location and size of the drop-down component, specified as [left bottom width height]. Position values are relative to the parent container. All measurements are in pixel units. This property value is identical to Position for drop-down components.

This property is read-only.

Outer location and size of drop-down component returned as [left bottom width height]. Position values are relative to the parent container. All measurements are in pixel units. This property value is identical to Position for drop-down components.

Layout options, specified as a GridLayoutOptions object. This property specifies options for components that are children of grid layout containers. If the component is not a child of a grid layout container (for example, it is a child of a figure or panel), then this property is empty and has no effect. However, if the component is a child of a grid layout container, you can place the component in the desired row and column of the grid by setting the Row and Column properties on the GridLayoutOptions object.

For example, this code places a drop-down in the third row and second column of its parent grid.

g = uigridlayout([4 3]);
dd = uidropdown(g);
dd.Layout.Row = 3;
dd.Layout.Column = 2;

To make the drop-down span multiple rows or columns, specify the Row or Column property as a two-element vector. For example, this drop-down spans columns 2 through 3:

dd.Layout.Column = [2 3];

Value changed callback, specified as one of these values:

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.

For more information about writing callbacks, see Callbacks in App Designer.

Drop-down menu opening callback, specified as one of these values:

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.

For more information about writing callbacks, see Callbacks in App Designer.

Clicked callback, specified as one of these values:

This callback function executes when the user clicks anywhere in the drop-down component.

This callback function can access specific information about the user’s interaction with the drop-down component. MATLAB passes this information in a ClickedData 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.InteractionInformation returns information about where the user clicked in the drop-down component. The ClickedData object is not available to callback functions specified as character vectors.

This table lists the properties of the ClickedData object.

This table lists the properties of the InteractionInformation object associated with the drop-down component.

For more information about writing callbacks, see Callbacks in App Designer.

Example: Display Data When Drop-Down Component Is Clicked

Create a drop-down component with items that represent groceries and item data that represents their cost. Specify a ClickedFcn callback function named displayCost that executes when a user clicks the component. In the displayCost function:

To try this example, save the code in a new script and run it. Click an item in the drop-down component to display its cost.

fig = uifigure;
dd = uidropdown(fig);
dd.Items = ["Apple","Banana","Orange"];
dd.ItemsData = [1.2,0.5,1.2];
dd.ClickedFcn = @displayCost;

function displayCost(dd,event)
idx = event.InteractionInformation.Item;
if ~isempty(idx)
    fruit = dd.Items(idx);
    cost = dd.ItemsData(idx);
    disp(fruit + " cost $" + cost)
end
end

Object creation function, specified as one of these values:

For more information about specifying a callback as a function handle, cell array, or character vector, see Callbacks in App Designer.

This property specifies a callback function to execute when MATLAB creates the object. MATLAB initializes all property values before executing the CreateFcn callback. If you do not specify the CreateFcn property, then MATLAB executes a default creation function.

Setting the CreateFcn property on an existing component has no effect.

If you specify this property as a function handle or cell array, you can access the object that is being created using the first argument of the callback function. Otherwise, use the gcbo function to access the object.

Object deletion function, specified as one of these values:

For more information about specifying a callback as a function handle, cell array, or character vector, see Callbacks in App Designer.

This property specifies a callback function to execute when MATLAB deletes the object. MATLAB executes the DeleteFcn callback before destroying the properties of the object. If you do not specify the DeleteFcn property, then MATLAB executes a default deletion function.

If you specify this property as a function handle or cell array, you can access the object that is being deleted using the first argument of the callback function. Otherwise, use the gcbo function to access the object.

Callback interruption, specified as 'on' or 'off', 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.

This property determines if a running callback can be interrupted. There are two callback states to consider:

MATLAB determines callback interruption behavior whenever it executes a command that processes the callback queue. These commands include drawnow, figure, uifigure, getframe, waitfor, and pause.

If the running callback does not contain one of these commands, then no interruption occurs. MATLAB first finishes executing the running callback, and later executes the interrupting callback.

If the running callback does contain one of these commands, then the Interruptible property of the object that owns the running callback determines if the interruption occurs:

Callback queuing, specified as 'queue' or 'cancel'. The BusyAction property determines how MATLAB handles the execution of interrupting callbacks. There are two callback states to consider:

The BusyAction property determines callback queuing behavior only when both of these conditions are met:

Under these conditions, the BusyAction property of the object that owns the interrupting callback determines how MATLAB handles the interrupting callback. These are possible values of the BusyAction property:

This property is read-only.

Deletion status, returned as an on/off logical value of type matlab.lang.OnOffSwitchState.

MATLAB sets the BeingDeleted property to 'on' when the DeleteFcn callback begins execution. The BeingDeleted property remains set to 'on' until the component object no longer exists.

Check the value of the BeingDeleted property to verify that the object is not about to be deleted before querying or modifying it.

Parent container, specified as a Figure object created using the uifigure function, or one of its child containers: Tab, Panel, ButtonGroup, or GridLayout. If no container is specified, MATLAB calls the uifigure function to create a new Figure object that serves as the parent container.

Visibility of the object handle, specified as 'on', 'callback', or 'off'.

This property controls the visibility of the object in its parent's list of children. When an object is not visible in its parent's list of children, it is not returned by functions that obtain objects by searching the object hierarchy or querying properties. These functions include get, findobj, clf, and close. Objects are valid even if they are not visible. If you can access an object, you can set and get its properties, and pass it to any function that operates on objects.

This property is read-only.

Type of graphics object, returned as 'uidropdown'.

Object identifier, specified as a character vector or string scalar. You can specify a unique Tag value to serve as an identifier for an object. When you need access to the object elsewhere in your code, you can use the findobj function to search for the object based on the Tag value.

User data, specified as any MATLAB array. For example, you can specify a scalar, vector, matrix, cell array, character array, table, or structure. Use this property to store arbitrary data on an object.

If you are working in App Designer, create public or private properties in the app to share data instead of using the UserData property. For more information, see Share Data Within App Designer Apps.