GUI for keyboard pressed representing the push button

Hi,

Does it any way to represent the keyboard pressed for the callback of pushbutton? For example, when 'A' in computer keyboard is pressed, MATLAB GUI for pushbutton1 will be triggered automatically and do the corresponding callback. When 'B' from keyboard is pressed, then GUI will do the callback for pushbutton2.

This is especially want to develop for the blind people so that they can control the GUI by keyboard without the help of computer mouse.

Hope there is some suggestion and example of coding. Thank you.

[Amir Mohammad Alizadeh]

What I am trying to do is opposite of that, I want to associate a button push in GUI with "esc" key. Any suggestions please? Thank you

[Walter Roberson]

@Amir Mohammad Alizadeh

You can modify the escape key detection routine to directly call the callback function you would like associated with the button push. Or, alternately, you could modify the escape key detection routine to use the Java "Robot" class to simulate a button push.

Answer 1

[Matt Fig]

Yes. Simply put the callbacks for the correct pushbuttons in the keypressfcn of the figure. You may need an enormous switchyard if you have one button for each key on the keyboard.

function [] = fig_keypressfcn(varargin)
% The keypressfcn for the figure.
switch varargin{2}.Key
case 'a'
case 'b'
...

[Yeoh]

May I know what is the 'figure' that you mean? Because the push buttons for each key on the keyboard will generate the alphabets on the text box in GUI without any graphs or any figure.

Actually I have to create a new function? I mean where should I put the keypressfcn, in pushbutton callback? or the text field?

Thank you very very very much..

Answer 2

[Jiro Doke]

I assume you are using GUIDE to create your GUI. In that case, create a WindowKeyPressFcn for the figure (the figure is the main GUI window). Right click on the background of your GUI in GUIDE, and there should be a "WindowKeyPressFcn" callback for that. Then in the callback code, use switch statement to deal with different key presses:

function figure1_WindowKeyPressFcn(hObject, eventdata, handles)

switch eventdata.Key
  case 'a'
    <callback function corresponding to "a">
  case 'b'
    <callback function corresponding to "b"> 
  ...
end

You may also want to compare the uses of KeyPressFcn for the figure and for the uicontrol. Depending on how you want the key presses to behave when different things have focus, you may choose one over the other.

[Yeoh]

Good answer! Thank you very much. Now I know what the "figure" means. Anyway, how can I put the callback function, if I just want to show the alphabet pressed on text box?

I input

function ENTER_A_Callback(hObject, eventdata, handles)

a='A';

set(handles.text1,'String',a);

But there is an error message:

??? Input argument "handles" is undefined.

Is it I have to set anything in my callback function as well?

[Jiro Doke]

How are you calling that function (ENTER_A_Callback)? The syntax looks fine, but it's saying that the variable "handles" was not passed in when the function was called. Check the place that is calling the function.

[Yeoh]

Oh, at first I call the function (ENTER_A_callback) in the function figure1_WindowKeyPressFcn(hObject, eventdata, handles)

such as

switch eventdata.Key

case 'a'

ENTER_A_Callback();

case 'b'

ENTER_B_Callback();

end

May be in the WindowKeyPressFcn, it can't call the sub-function.

Then I try in this way:

switch eventdata.Key

case 'a'

set(handles.output,'String','A');

case 'b'

set(handles.output,'String','B');

end

Yeah, it works! The text box will display "A" when I press keyboard "A", so as for B.

Thank you very much.

[Muhammad Faheem Irfan]

Good answer.............

Answer 3

[Oleg Komarov]

A simple example which uses KeyPressFcn:

function [] = gui()
S.fh = figure('units','pixels',...
              'position',[500 200 200 100],...
              'menubar','none',...
              'name','gui',...
              'numbertitle','off',...
              'resize','off');
S.pb = uicontrol('style','push',...
                 'units','pix',...
                 'position',[10 10 180 40],...
                 'fontsize',14,...
                 'string','Hi!');          
S.tx = uicontrol('style','text',...
                 'units','pix',...
                 'position',[10 55 180 40],...
                 'string','goodbye',...
                 'fontsize',23);

set(S.pb,'callback'   ,{@pb_call,S})
% Check if 'p' is pressed when focus on button and exec callback
set(S.pb,'KeyPressFcn',{@pb_kpf ,S});
% Check if 'p' is pressed when focus on figure and exec callback
set(S.fh,'KeyPressFcn',{@pb_kpf ,S});

% Callback for pushbutton, prints Hi! in cmd window
function pb_call(varargin)
S = varargin{3};  % Get the structure.
set(S.tx,'String', get(S.pb,'String'))

% Do same action as button when pressed 'p'
function pb_kpf(varargin)
if varargin{1,2}.Character == 'p'
    pb_call(varargin{:})
end

Oleg

[Yeoh]

Hi, thank you for answer my question. But I cannot really understand the varargin. If I want to output in the text field in GUI instead of command window, is it I no need to do the varargin?

I think you are trying to position the mouse onto the pushbutton by writing the coding. Am I right?

Thanks again.

[Oleg Komarov]

I'm not trying to position the mouse. I'm using the KeyPressFcn callback.

I modified the code above to update a statis text box. Try to run it.

[Yeoh]

Yeah, it works.. But I'm using GUIDE to create my GUI. So can I add those coding in my M-file? Thank you.

Answer 4

[Jonathan]

I got a question here if I want to do a case where I press 'CTRL+a' how do I write it in the case?

[Walter Roberson]

You need to check that strcmp(eventdata.Modifier,'control') is true. That cannot be done directly in the case label for 'a' but it can be done within the body... or you could test the modifier before the switch and use different switch trees for the different modifiers.

Answer 5

[SN MJTHD]

Dear Matlab Experts

I am doing a similar work but there is a difference. For the moment, I`m using two Push Buttons in my GUI with names LEFT and RIGHT. but I have Three Conditions like Left, Right and NoResponse. NoResponse means non of Left or Right Push Buttons are pushed.

Now I`m trying to use both keyboard and push buttons for my purpose. For example "S" key as Left Push Button and "L" key as Right Push Button and if non of them are pushed NoResponse be done.

I tried many ways but I encountered different errors.

I appreciate any help.