Introduction to Matlab’s Graphical User Interface (GUI) Type “guide” “Guide” creates interface on a Figure window and code in an M-file. Some hidden code. The M-file and the Figure window usually have the same name. We add “objects” in the “Layout editor” and complete “Callback functions” in M-file editor.

Try it. Type “guide”. The layout window appears. Add a slider and an edit text box. We want the text to represent the “value” of the slider. Right click in the slider, go down to “view callbacks”, and select “Callback”

Try it. You are invited to save the untitled document and then taken to an M-file editor, with the start of you callback function already written. Notice that the M-file has the same name as the figure.

Handles The main figure has a “handle” in the Matlab environment. Handles allow Matlab to keep track of figures and graphic objects. Within the main figure each of our objects (the slider and the text box) also have a handle. Child objects.

Handles We differentiate between or identify objects by their handle. Matlab has functions to keep track of and list these gui handles. Run the M-file by typing “h= ”. It doesn’t do much yet! Don’t confuse the Figure with the Layout editor.

Handles The handle of the figure is returned in variable “h”. Although “h” only admits to being a double, it gives us access to all the properties of the figure. get(h) returns a copy of the figure’s (object’s) properties including its children. The “children” are the objects that we have placed on the figure: slider and edit text.

Handles, Try it Type “maindetails=get(h)” maindetails lists all the properties in the figure. The structure includes handles to the child objects. We can use the handles to gain access to the child objects and alter their properties.

Properties, get() and set() We can retrieve a copy of the values associated with a graphic object through its handle by using S=get(h) The structure contains all the properties of the graphic object. However, since it is a copy we cannot change the actual information associated with the graphic object.

Properties, get() and set() So in true “OO’” style we must use an access method/function to adjust parameters.. Set(h,'PropertyName',Propert yValue) Get(h) or Get(h, ‘PropertyName’) returns the property. Note ‘quotes’

Properties, get() and set() Alter the ‘visible’ property of the slider using the handles to the child objects of your gui. Put it back to what it was. You will need to get the child handles array from the main gui and use set to change the visible property.

Example g=test get(g) cld=get(g.Children) cld=get(g, 'Children') set(cld(1), 'Visible', 'off') set(cld(1), 'Visible', 'on')

Reference to objects In the GUI an object’s handles are passed to the callback function in the variable hObject. Also, the self generated code produces a list of all objects handles in the structure “handles” (see later).

Other callbacks CreateFcn DeleteFcn ButtonDownFcn More….

Guihandles() This function returns an structure of handles of all handle in the gui. It passes the structure to your callback function in the variable “handles” So we can access other objects through this structure. handles.edit1 for example gives us the handle of the edit box.

Write some callbacks Write a call back to display the slider’s position in the edit box. Do the same, but make the slider move (‘value’) when a value between 0 and 1 is entered in the edit window.

Properties we need We want to display the value of the slider in the edit box. So we need something to retrieve the value from the slider. And we need something to give the value to the edit box.

Properties we need We use slider ‘value’ And edit text ‘string’. Also need string conversion from num2str and str2num

Examples In the slider1 callback get(hObject, 'Value') set(handles.edit1, 'String', num2str(v)) In the edit1 callback s=get(hObject, 'String') set(handles.slider1, 'Value', str2num(s))

Plot picture to axis Image(a) will send an image to the current axis You may need –gca Get current axes –axes Set current axes

Lets load a picture Place an axes on your form. Place a button which is going to load and display a picture. Write the callback.

Example In button1 callback im=imread('test2.bmp'); image(im)