MATLAB Creating Graphical User Interfaces

11 Code a Programmatic UI

disp(['Slider moved to ' newval]);

end

This callback function displays the value of the slider when the end user adjusts it.

A benefit of specifying callbacks as function handles is that MATLAB checks the

function for syntax errors and missing dependencies when you assign the callback to the

component. If there is a problem in the callback function, then MATLAB returns an error

immediately instead of waiting for the end user to trigger the callback. This behavior

helps you to find problems in your code before the end user encounters them.

Note:If you want to use an existing function that does not support the hObject and

callbackdata arguments, then you can specify it as an anonymous function. For

example,

uicontrol('Style','slider','Callback',@(hObject,callbackdata)myfunction(x));

In this case, x is an input argument to the function, myfunction. See “Anonymous

Functions” for more information.

Specify a Cell Array

Use a cell array to specify a callback function that accepts input arguments that you

want to use in the function. The first element in the cell array is a function handle.

The other elements in the cell array are the input arguments to the function, separated

by commas. For example, this code creates a push button component and specifies its

callback to be a cell array containing the function handle, @pushbutton_callback, and

one input argument, myvar. To see how it works, copy and paste this code into an editor

and run it.

function myui()

myvar = 5;

figure

uicontrol('Style','pushbutton',...

'Callback',{@pushbutton_callback,myvar});

end

function pushbutton_callback(hObject,callbackdata,x)

display(x);

end

The function definition must define two input arguments, hObject and callbackdata,

followed by any additional arguments the function uses. Handle Graphics automatically

passes the hObject and callbackdata arguments when it calls the function. If you

define additional input arguments, then the values you pass to the callback must exist in

the workspace when the end user triggers the callback.