Callbacks for Specific ComponentsCoding the behavior of a UI component involves specific tasks
that are unique to the type of component you are working with. This
topic contains simple examples of callbacks for each type of component.
The examples are written for GUIDE unless otherwise stated. For general
information about coding callbacks, see
or .How to Use the Example CodeIf you are working in GUIDE, then right-click on the component
in your layout and select the appropriate callback property from the View
Callbacks menu. Doing so creates an empty callback function
that is automatically associated with the component. The specific
function name that GUIDE creates is based on the component's Tag property,
so your function name might be slightly different than the function
name in the example code. Do not change the function name that GUIDE
creates in your code. To use the example code in your UI, copy the
code from the example's function body into your function's
body.If you are creating a UI programmatically, (without GUIDE),
then you can adapt the example code into your code. To adapt an example
into your code, omit the third input argument, handles,
from the function definition. Also, replace any references to the handles array
with the appropriate object handle.
To associate the callback function
with the component, set the component's callback property to be a
handle to the callback function. For example, this command creates
a push button component and sets the Callback property
to be a handle to the function, pushbutton1_callback.pb = uicontrol('Style','pushbutton','Callback',@pushbutton1_Callback); Push ButtonThis code is an example of a push button callback function in
GUIDE. Associate this function with the push button Callback property
to make it execute when the end user clicks on the push button.function pushbutton1_Callback(hObject, eventdata, handles)
handle to pushbutton1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
display('Goodbye');
close(gcf);The first line of code, display('Goodbye'),
displays the string, 'Goodbye', in the Command
Window. The next line gets a handle to the UI window using
and then closes it.Toggle ButtonThis code is an example of an example of a toggle button callback
function in GUIDE. Associate this function with the toggle button Callback property
to make it execute when the end user clicks on the toggle button.function togglebutton1_Callback(hObject,eventdata,handles)
handle to togglebutton1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hint: get(hObject,'Value') returns toggle state of togglebutton1
button_state = get(hObject,'Value');
if button_state == get(hObject,'Max')
display('down');
elseif button_state == get(hObject,'Min')
display('up');
endThe toggle button's Value property
matches the Min property when the toggle button
is up. The Value changes to the Max value
when the toggle button is depressed. This callback function gets the
toggle button's Value property and then
compares it with the Max and Min properties.
If the button is depressed, then the function displays 'down' in
the Command Window. If the button is up, then the function displays 'up'.Radio ButtonThis code is an example of a radio button callback function
in GUIDE. Associate this function with the radio button Callback property
to make it execute when the end user clicks on the radio button.function radiobutton1_Callback(hObject, eventdata, handles)
handle to radiobutton1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hint: get(hObject,'Value') returns toggle state of radiobutton1
if (get(hObject,'Value') == get(hObject,'Max'))
display('Selected');
display('Not selected');
endThe radio button's Value property
matches the Min property when the radio button
is not selected. The Value changes to the Max value
when the radio button is selected. This callback function gets the
radio button's Value property and then
compares it with the Max and Min properties.
If the button is selected, then the function displays 'Selected' in
the Command Window. If the button is not selected, then the function
displays 'Not selected'.Note&&
Use a button group to manage exclusive selection behavior for
radio buttons. See
for more information. Check BoxThis code is an example of a check box callback function in
GUIDE. Associate this function with the check box Callback property
to make it execute when the end user clicks on the check box.function checkbox1_Callback(hObject, eventdata, handles)
handle to checkbox1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hint: get(hObject,'Value') returns toggle state of checkbox1
if (get(hObject,'Value') == get(hObject,'Max'))
display('Selected');
display('Not selected');
endThe check box's Value property matches
the Min property when the check box is not selected.
The Value changes to the Max value
when the check box is selected. This callback function gets the check
box's Value property and then compares
it with the Max and Min properties.
If the check box is selected, the function displays 'Selected' in
the Command Window. If the check box is not selected, it displays 'Not
selected'.Edit Text FieldThis code is an example of a callback for an edit text field
in GUIDE. Associate this function with the uicontrol's Callback property
to make it execute when the end user types inside the text field.function edit1_Callback(hObject, eventdata, handles)
handle to edit1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit1 as text
str2double(get(hObject,'String')) returns contents as double
input = get(hObject,'String');
display(input);When the end user types characters inside the text field and
presses the Enter key, the callback function retrieves
the string value and displays it in the Command Window.To enable users to enter multiple lines of text, set the Max and Min properties
to numeric values that satisfy Max - Min & 1.
For example, set Max to 2, and Min to 0 to
satisfy the inequality. In this case, the callback function triggers
when the end user clicks on an area in the UI that is outside of the
text field.Retrieve Numeric ValuesIf you want to interpret the contents of an edit text field
as numeric values, then convert the characters to numbers using the
function. The str2double function
returns NaN for nonnumeric input.This code is an example of an edit text field callback function
that interprets the user's input as numeric values.function edit1_Callback(hObject, eventdata, handles)
handle to edit1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit1 as text
% str2double(get(hObject,'String')) returns contents as a double
input = str2double(get(hObject,'string'));
if isnan(input)
errordlg('You must enter a numeric value','Invalid Input','modal')
uicontrol(hObject)
display(input);
endWhen the end user enters values into the edit text field and
presses the Enter key, the callback function gets
the value of the String property and converts it
to a numeric value. Then, it checks to see if the value is NaN (nonnumeric).
If the input is NaN, then the callback presents
an error dialog box.SliderThis code is an example of a slider callback function in GUIDE.
Associate this function with the slider Callback property
to make it execute when the end user moves the slider.function slider1_Callback(hObject, eventdata, handles)
handle to slider1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'Value') returns position of slider
get(hObject,'Min') and get(hObject,'Max') to determine...
slider_value = get(hObject,'Value');
display(slider_value);When the end user moves the slider, the callback function gets
the current value of the slider and displays it in the Command Window.
By default, the slider's range is [0, 1]. To modify the range,
set the slider's Max and Min properties
to the maximum and minimum values, respectively.List BoxPopulate Items in the List BoxIf you are developing a UI using GUIDE, use the list box CreateFcn callback
to add items to the list box.This code is an example of a list box CreateFcn callback
that populates the list box with the items, Red, Green,
and Blue.function listbox1_CreateFcn(hObject, eventdata, handles)
handle to listbox1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
empty - handles not created until after all CreateFcns
% Hint: listbox controls usually have a white background on Windows.
if ispc && isequal(get(hObject,'BackgroundColor'), ...
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
set(hObject,'String',{'Red';'Green';'Blue'});The
last line, set(hObject,'String',{'Red';'Green';'Blue'}),
populates the contents of the list box.If you are developing a UI programmatically (without GUIDE),
then populate the list box when you create it. For example:function myui()
uicontrol('Style','Listbox',...
'String',{'Red';'Green';'Blue'},...
'Position',[40 70 80 50]);
endChange the Selected ItemWhen the end user selects a list box item, the list box's Value property
changes to a number that corresponds to the item's position
in the list. For example, a value of 1 corresponds
to the first item in the list. If you want to change the selection
in your UI code, then change the Value property
to another number between 1 and the number of items
in the list.For example, you can use the handles structure
in GUIDE to access the list box and change the Value property:set(handles.listbox1,'Value',2)The first argument, handles.listbox1, might
be different in your code, depending on the value of the list box Tag property.Write the Callback FunctionThis code is an example of a list box callback function in GUIDE.
Associate this function with the list box Callback property
to make it execute when a selects an item in the list box.function listbox1_Callback(hObject, eventdata, handles)
handle to listbox1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hints: contents = cellstr(get(hObject,'String')) returns contents
% contents{get(hObject,'Value')} returns selected item from listbox1
items = get(hObject,'String');
index_selected = get(hObject,'Value');
item_selected = items{index_selected};
display(item_selected);When the end user selects an item in the list box, the callback
function performs the following tasks:Gets all the items in the list box and stores them
in the variable, items.Gets the numeric index of the selected item and stores
it in the variable, index_selected.Gets the string value of the selected item and stores
it in the variable, item_selected.Displays the selected item in the MATLAB® Command
Window.The example,
shows how to populate a list box
with directory names.Pop-Up MenuPopulate Items in the Pop-Up MenuIf you are developing a UI using GUIDE, use the pop-up menu CreateFcn callback
to add items to the pop-up menu.This code is an example of a pop-up menu CreateFcn callback
that populates the menu with the items, Red, Green,
and Blue.function popupmenu1_CreateFcn(hObject, eventdata, handles)
handle to popupmenu1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
empty - handles not created until after all CreateFcns
% Hint: popupmenu controls usually have a white background on Windows.
if ispc && isequal(get(hObject,'BackgroundColor'),...
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
set(hObject,'String',{'Red';'Green';'Blue'});The
last line, set(hObject,'String',{'Red';'Green';'Blue'}),
populates the contents of the pop-up menu.If you are developing a UI programmatically (without GUIDE),
then populate the pop-up menu when you create it. For example:function myui()
uicontrol('Style','popupmenu',...
'String',{'Red';'Green';'Blue'},...
'Position',[40 70 80 20]);
endChange the Selected ItemWhen the end user selects an item, the pop-up menu's Value property
changes to a number that corresponds to the item's position
in the menu. For example, a value of 1 corresponds
to the first item in the list. If you want to change the selection
in your UI code, then change the Value property
to another number between 1 and the number of items
in the menu.For example, you can use the handles structure
in GUIDE to access the pop-up menu and change the Value property:set(handles.popupmenu1,'Value',2)The first argument, handles.popupmenu1, might
be different in your code, depending on the value of the pop-up menu Tag property.Write the Callback FunctionThis code is an example of a pop-up menu callback function in
GUIDE. Associate this function with the pop-up menu Callback property
to make it execute when the end user selects an item from the menu.function popupmenu1_Callback(hObject, eventdata, handles)
handle to popupmenu1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
% Hints: contents = cellstr(get(hObject,'String')) returns contents...
contents{get(hObject,'Value')} returns selected item...
items = get(hObject,'String');
index_selected = get(hObject,'Value');
item_selected = items{index_selected};
display(item_selected);When the end user selects an item in the pop-up menu, the callback
function performs the following tasks:Gets all the items in the pop-up menu and stores them
in the variable, items.Gets the numeric index of the selected item and stores
it in the variable, index_selected.Gets the string value of the selected item and stores
it in the variable, item_selected.Displays the selected item in the MATLAB Command
Window.PanelMake the Panel Respond to Button ClicksYou can create a callback function that executes when the end
user right-clicks or left-clicks on the panel. If you are working
in GUIDE, then right-click the panel in the layout and select View Callbacks & ButtonDownFcn to create the callback function.This code is an example of a ButtonDownFcn callback
in GUIDE.function uipanel1_ButtonDownFcn(hObject, eventdata, handles)
handle to uipanel1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
display('Mouse button was pressed');When the end
user clicks on the panel, this function displays the text, 'Mouse
button was pressed', in the Command Window.Resize the Window and PanelBy default, GUIDE UIs cannot be resized, but you can override
this behavior by selecting Tools & GUI Options and setting Resize
behavior to Proportional.Programmatic UIs can be resized by default, and you can change
this behavior by setting the Resize property
of the figure on or off.When your UI is resizable, the position of components in the
window adjust as the user resizes it. If you have a panel in your
UI, then the panel's size will change with the window's
size. Use the panel's SizeChangedFcn callback
to make your UI perform specific tasks when the panel resizes.This code is an example of a panel's SizeChangedFcn callback
in a GUIDE UI. When the end user resizes the window, this function
modifies the font size of static text inside the panel.function uipanel1_SizeChangedFcn(hObject, eventdata, handles)
handle to uipanel1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
set(hObject,'Units','Points')
panelSizePts = get(hObject,'Position');
panelHeight = panelSizePts(4);
set(hObject,'Units','normalized');
newFontSize = 10 * panelHeight / 115;
texth = findobj('Tag','text1');
set(texth,'FontSize',newFontSize);If your UI has nested panels, then they will resize from the
inside-out (in child-to-parent order).Note:&&
To make the text inside a panel resize automatically, set the fontUnits property
to 'normalized'.Button GroupButton groups are similar to panels, but they also manage exclusive
selection of radio buttons and toggle buttons. When a button group
contains multiple radio buttons or toggle buttons, the button group
allows the end user to select only one of them.Do not code callbacks for the individual buttons that are inside
a button group. Instead, use the button group's SelectionChangedFcn callback
to respond when the end user selects a button.This code is an example of a button group SelectionChangedFcn callback
that manages two radio buttons and two toggle buttons.function uibuttongroup1_SelectionChangedFcn(hObject, eventdata, handles)
handle to the selected object in uibuttongroup1
% eventdata
structure with the following fields
% EventName: string 'SelectionChanged' (read only)
% OldValue: handle of the previously selected object or empty
% NewValue: handle of the currently selected object
structure with handles and user data (see GUIDATA)
switch get(eventdata.NewValue,'Tag') % Get Tag of selected object.
case 'radiobutton1'
display('Radio button 1');
case 'radiobutton2'
display('Radio button 2');
case 'togglebutton1'
display('Toggle button 1');
case 'togglebutton2'
display('Toggle button 2');
endWhen the end user selects a radio button or toggle button in
the button group, this function determines which button the user selected
based on the button's Tag property. Then,
it executes the code inside the appropriate case.Note:&&
The button group's SelectedObject property
contains a handle to the button that user selected. You can use this
property elsewhere in your UI code to determine which button the user
selected.Menu ItemThe code in this section contains example callback functions
that respond when the end user selects Edit & Copy & To File in this menu.
% --------------------------------------------------------------------
function edit_menu_Callback(hObject, eventdata, handles)
handle to edit_menu (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
display('Edit menu selected');
% --------------------------------------------------------------------
function copy_menu_item_Callback(hObject, eventdata, handles)
handle to copy_menu_item (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
display('Copy menu item selected');
% --------------------------------------------------------------------
function tofile_menu_item_Callback(hObject, eventdata, handles)
handle to tofile_menu_item (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
[filename,path] = uiputfile('myfile.m','Save file name');The
function names might be different in your UI, depending on the tag
names you specify in the GUIDE Menu Editor.The callback functions trigger in response to these actions:When the end user selects the Edit menu,
the edit_menu_Callback function displays the text, 'Edit
menu selected', in the MATLAB Command Window.When the end user hovers the mouse over the Copy menu
item, the copy_menu_item_Callback function displays
the text, 'Copy menu item selected', in the MATLAB Command
Window.When the end user clicks and releases the mouse button
on the To File menu item, the tofile_menu_item_Callback function
displays a dialog box that prompts the end user to select a destination
folder and file name.The tofile_menu_item_Callback function calls
function to prompt
the end user to supply a destination file and folder. If you want
to create a menu item that prompts the user for an existing file,
for example, if your UI has an Open File menu
item, then use the
function.When you create a cascading menu like this one, the intermediate
menu items trigger when the mouse hovers over them. The final, terminating,
menu item triggers when the mouse button releases over the menu item.How to Update a Menu Item CheckYou can add a check mark next to a menu item to indicate that
an option is enabled. In GUIDE, you can select Check
mark this item in the Menu Editor to make the menu item
checked by default. Each time the end user selects the menu item,
the callback function can turn the check on or off.This code shows how to change the check mark next to a menu
item.if strcmp(get(hObject,'Checked'),'on')
set(hObject,'Checked','off');
set(hObject,'Checked','on');
function compares
two strings and returns true when they match. In
this case, it returns true when the menu item's Checked property
matches the string, 'on'.See
for more information about
creating menu items in GUIDE. See
for more information
about creating menu items programmatically.TableThis code is an example of the table callback function, CellSelectionCallback.
Associate this function with the table CellSelectionCallback property
to make it execute when the end user selects cells in the table.function uitable1_CellSelectionCallback(hObject, eventdata, handles)
handle to uitable1 (see GCBO)
% eventdata
structure with the following fields
Indices: row and column indices of the cell(s) currently selected
structure with handles and user data (see GUIDATA)
data = get(hObject,'Data');
indices = eventdata.I
r = indices(:,1);
c = indices(:,2);
linear_index = sub2ind(size(data),r,c);
selected_vals = data(linear_index);
selection_sum = sum(sum(selected_vals))When the end user selects cells in the table, this function
performs the following tasks:Gets all the values in the table and stores them in
the variable, data.Gets the indices of the selected cells. These indices
correspond to the rows and columns in data.Converts the row and column indices into linear indices.
The linear indices allow you to select multiple elements in an array
using one command.Gets the values that the end user selected and stores
them in the variable, selected_vals.Sums all the selected values and displays the result
in the Command Window.This code is an example of the table callback function, CellEditCallback.
Associate this function with the table CellEditCallback property
to make it execute when the end user edits a cell in the table.function uitable1_CellEditCallback(hObject, eventdata, handles)
handle to uitable1 (see GCBO)
% eventdata
structure with the following fields
% Indices: row and column indices of the cell(s) edited
% PreviousData: previous data for the cell(s) edited
% EditData: string(s) entered by the user
% NewData: EditData or its converted form set on the Data property.
% Empty if Data was not changed
% Error: error string when failed to convert EditData
data = get(hObject,'Data');
data_sum = sum(sum(data))When the end user finishes
editing a table cell, this function gets all the values in the table
and calculates the sum of all the table values. The ColumnEditable property
must be set to true in at least one column to allow
the end user to edit cells in the table. For more information about
creating tables and modifying their properties in GUIDE, see .AxesThe code in this section is an example of an axes ButtonDownFcn that
triggers when the end user clicks on the axes.
function axes1_ButtonDownFcn(hObject, eventdata, handles)
handle to axes1 (see GCBO)
% eventdata
reserved - to be defined in a future version of MATLAB
structure with handles and user data (see GUIDATA)
pt = get(hObject,'CurrentPoint')The coordinates of
the pointer display in the MATLAB Command Window when the end
user clicks on the axes (but not when that user clicks on another
graphics object parented to the axes).Note:&&
Most MATLAB plotting functions clear the axes and reset
a number of axes properties, including the ButtonDownFcn,
before plotting data. To create an interface that lets the end user
plot data interactively, consider providing a component such as a
push button to control plotting. Such components' properties
are unaffected by the plotting functions.
If you must use the axes ButtonDownFcn to
plot data, then use functions such as , , and .
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