Transcript Introduction to Matlab’s Graphical User Interface (GUI)

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=<yourfunctionname>”.
• 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
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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)