How can I relate a pushbutton to position?

Hi! I'm making a piano on matlab & can't figure out how to have matlab recognize if the user pushed on a key based on the position of the key itself. Basically, if the user clicks on the right key I want a "Good Job" message to come up & "Error" message to come up if they click the wrong one. I'm thinking to use an if statement but everything I try isnt working. Here is my code so far:

%Paino Figure w/ pushbuttons
function PianoImage_HBraslawsce()
f=figure();
set(f, 'MenuBar','none'); %Remove menu bar
set(f,'NumberTitle','off');
set(f,'Name', 'Note Learner'); %Change name
%Each key as a pushbutton
KEYC = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.15 .15 .1 .45]);
KEYD = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.25 .15 .1 .45]);
KEYE = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.35 .15 .1 .45]);
KEYF = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.45 .15 .1 .45]);
KEYG = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.55 .15 .1 .45]);
KEYA = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.65 .15 .1 .45]);
KEYB = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.75 .15 .1 .45]);
KEYCHI = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.85 .15 .1 .45]);
KEYCSH = uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized','position',[.20 .3 .08 .3]);
KEYEb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized','position',[.30 .3 .08 .3]);
KEYFSH=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized','position',[.5 .3 .08 .3]);
KEYAb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized','position',[.60 .3 .08 .3]);
KEYBb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized','position',[.70 .3 .08 .3]);
%Keys callback
set(KEYC,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYCSH,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYD,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYE,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYEb,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYF,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYFSH,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYG,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYAb,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYA,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYBb,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYB,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
set(KEYCHI,'Callback',{@keypressed,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI})
end

function keypressed(x,y,KEYC,KEYCSH,KEYD,KEYE,KEYEb,KEYF,KEYFSH,KEYG,KEYA,KEYAb,KEYB,KEYBb,KEYCHI)
x;
y;
KEYC;
KEYCSH;
KEYD;
KEYE;
KEYEb;
KEYF;
KEYFSH;
KEYG;
KEYA;
KEYAb;
KEYB;
KEYBb;
KEYCHI;

KEYC='C';
KEYCSH='C#';
KEYD='D';
KEYE='E';
KEYEb='Eb';
KEYF='F';
KEYFSH='F#';
KEYG='G';
KEYA='A';
KEYAb='Ab';
KEYB='B';
KEYBb='Bb';
KEYCHI='C(high)';

'C'=='position',[.15 .15 .1 .45];
'C#'=='position',[.20 .3 .08 .3];
'D'=='position',[.25 .15 .1 .45];
'E'=='position',[.35 .15 .1 .45];
'Eb'=='position',[.30 .3 .08 .3];
'F'=='position',[.45 .15 .1 .45];
'F#'=='position',[.5 .3 .08 .3];
'G'=='position',[.55 .15 .1 .45];
'Ab'=='position',[.60 .3 .08 .3];
'A'=='position',[.65 .15 .1 .45];
'Bb'=='position',[.70 .3 .08 .3];
'B'=='position',[.75 .15 .1 .45];
'C(high)'=='position',[.85 .15 .1 .45];
end

[Christophe]

I do not understand what you are trying to do.

The code at the bottom from the line

C'=='position',[.15 .15 .1 .45];

is not correct.

Anyway, in your x variable, you have the uicontrol handle. You have access to all the uicontrol properties of the button you push.

[Han]

I'm going to have the letters pop up on the screen and the user has to click the correct key based off of that letter. I honestly have no clue what I'm doing and thought relating the position of the button to the letter would be correct.

Answer 1

[Geoff Hayes]

Han - try using the UserData property of the pushbutton to store the key that the button represents. That way, when the button is pressed and the callback fires, you can use (get) this property to compare against the letters that have popped up on screen. Your code could look something like

function PianoImage_HBraslawsce()

    f=figure();
    set(f, 'MenuBar','none'); %Remove menu bar
    set(f,'NumberTitle','off');
    set(f,'Name', 'Note Learner'); %Change name
    %Each key as a pushbutton
    KEYC = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.15 .15 .1 .45], 'UserData', 'C','Callback',@keypressed);
    KEYD = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.25 .15 .1 .45], 'UserData', 'D','Callback',@keypressed);
    KEYE = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.35 .15 .1 .45], 'UserData', 'E','Callback',@keypressed);
    KEYF = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.45 .15 .1 .45], 'UserData', 'F','Callback',@keypressed);
    KEYG = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.55 .15 .1 .45], 'UserData', 'G','Callback',@keypressed);
    KEYA = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized','position',[.65 .15 .1 .45], 'UserData', 'A','Callback',@keypressed);
    KEYB = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.75 .15 .1 .45], 'UserData', 'B','Callback',@keypressed);
    KEYCHI = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.85 .15 .1 .45], 'UserData', 'C(high)','Callback',@keypressed);
    KEYCSH = uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.20 .3 .08 .3], 'UserData', 'C#','Callback',@keypressed);
    KEYEb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.30 .3 .08 .3], 'UserData', 'Eb','Callback',@keypressed);
    KEYFSH=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.5 .3 .08 .3], 'UserData', 'F#','Callback',@keypressed);
    KEYAb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.60 .3 .08 .3], 'UserData', 'Ab','Callback',@keypressed);
    KEYBb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.70 .3 .08 .3], 'UserData', 'Bb','Callback',@keypressed);

    function keypressed(hObject, eventdata)
        fprintf('You have pressed key %s\n', get(hObject, 'UserData'));
    end

end

I've nested the callback within the main function for convenience but also just in case you need to access those variables declared there. This avoids the need to pass the button handles into the callback function whose signature has now been reduced to simply

function keypressed(hObject, eventdata)

In your callback you were overwriting the pushbutton handle inputs with strings (this isn't something you really want or should do as you are changing the purpose of the variable from a function handle to a string). These strings are now stored in the UserData property for each button. We can then use the get function to retrieve that key string.

Note that when comparing this string against whatever note you've displayed, you will want to use the strcmp function (using == with strings will generally only work if the strings being compared have the same number of characters).

[Mrutyunjaya Hiremath]

@ Geoff Hayes, Hi

Clean, compact and nicely explained.

[Han]

Oh okay! I understand now. If you could answer another question that would be great! I have an excel file which contains each possible level of the game. I then used xlsread to transfer the data over to Matlab and then used ranperm to randomly select a letter possibility. For example level one could be letters {'C D E F'}. I want these letters to pop up above the piano figure and have the user click the corresponding letters. I'm not sure how to have Matlab know whether the user is clicking on the correct key or not.

[Geoff Hayes]

The following code will show you how to check whether the correct key is pressed or not. The following piece just sets up the array of keys and prints them out to the command line. This code should be put in the main function just after the buttons have been created.

    randomKeysToPress = {'C', 'D', 'F#'};
    fprintf('Please press the following keys: ');
    for key = randomKeysToPress
        fprintf(' %s', char(key));
    end
    fprintf('\n');
    atKey = 1;

We have two variables - randomKeysToPress and atKey. The latter is an index into the former and we will use that to see if the user pressed the correct key or not. Since our callback is nested, it has access to these two variables.

    function keypressed(hObject, eventdata)
        fprintf('You have pressed key %s\n', get(hObject, 'UserData'));
        if strcmp(randomKeysToPress{atKey}, get(hObject, 'UserData')) == 1
            fprintf('You have selected the correct key!\n');
            atKey = atKey + 1;
            if atKey > length(randomKeysToPress)
                fprintf('Game over!!!\n');
            end
        else
            fprintf('You have selected the wrong key! :( \n');
        end
            
    end

Every time the user selects the correct key, we increment atKey index so that we can validate the next key press.

[Han]

This helps me out so much!! Thank you again

[Han]

Actually I have one more qestion, is there any way I can display the random letters above the figure?

[Geoff Hayes]

Yes, you can use a text style uicontrol.

[Han]

So my teacher told me that what I'm using is global variables and we aren't allowed to use those. Is there any way I can do this code with more programmer defined functions. Here is my code so you can see what I have.

%Paino Figure w/ pushbuttons
function PianoImage_HBraslawsce()%<SM:PDF_CALL>

    f=figure();
    set(f, 'MenuBar','none'); %Remove menu bar
    set(f,'NumberTitle','off');
    set(f,'Name', 'Note Learner'); %Change name
    %Each key as a pushbutton
    %<SM:PLOT>
    KEYC = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.15 .15 .1 .45], 'UserData', 'C','Callback',@keypressed);
    KEYD = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.25 .15 .1 .45], 'UserData', 'D','Callback',@keypressed);
    KEYE = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.35 .15 .1 .45], 'UserData', 'E','Callback',@keypressed);
    KEYF = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.45 .15 .1 .45], 'UserData', 'F','Callback',@keypressed);
    KEYG = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.55 .15 .1 .45], 'UserData', 'G','Callback',@keypressed);
    KEYA = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.65 .15 .1 .45], 'UserData', 'A','Callback',@keypressed);
    KEYB = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.75 .15 .1 .45], 'UserData', 'B','Callback',@keypressed);
    KEYCHI = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],'units','normalized',...
        'position',[.85 .15 .1 .45], 'UserData', 'C(high)','Callback',@keypressed);
    KEYCSH = uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.20 .3 .08 .3], 'UserData', 'C#','Callback',@keypressed);
    KEYEb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.30 .3 .08 .3], 'UserData', 'Eb','Callback',@keypressed);
    KEYFSH=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.5 .3 .08 .3], 'UserData', 'F#','Callback',@keypressed);
    KEYAb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.60 .3 .08 .3], 'UserData', 'Ab','Callback',@keypressed);
    KEYBb=uicontrol('style','pushbutton','backgroundcolor',[0 0 0],'units','normalized',...
        'position',[.70 .3 .08 .3], 'UserData', 'Bb','Callback',@keypressed);

 %MATLAB read data
[~,~,Array]=xlsread('Notes'); %<SM:READ>

%slices out notes only
Notes=Array(1:1,2:16); %<SM:SLICE>
Choices=Notes(1:1,1:15); %slices out notes only
NoteOptions=numel(Choices); %randomizes outputted notes
set1=randperm(NoteOptions); %<SM:RANDUSE>
x=Choices(set1(1:1));


splitb=split(x);%cuts out each note from string
random1 = splitb 
     
    for key = random1 %<SM:FOR>
        sprintf(' %s', char(key));
    end
    newline;
    
    atKey1=1;
    
        function keypressed(hObject, eventdata) %callback for key clicked
        if strcmp(random1{atKey1}, get(hObject, 'UserData'))==1 %<SM:ROP>
            (msgbox('Good Job!'));
            atKey1 = atKey1 + 1; %<SM:RTOTAL>
           if atKey1 > length(random1)
              (msgbox('Good Job! You have completed the round. Start over to keep on learning!'));
            end 
        else
            msgbox('ERROR. Please try again.');
        end
            
        end  

end

[Geoff Hayes]

Han - i would argue that the above code does not use global variables but variables that are shared between parent and nested function. Is the concern with the atKey and random1 variables?

[Han]

Yes, because they come up light blue in my code and I guess this is not allowed.

[Geoff Hayes]

I supposed you could use guidata which is a function that allows you to set and retrieve data that is associated with a figure (in your case, the GUI). This function is used in GUIDE-based GUIs but can be used for GUIs that are created programmatically as well. What you need to do is to create a structure that will manage the data that you want to share with your callback

splitb=split(x);%cuts out each note from string
sharedData.random1 = splitb 

for key = sharedData.random1 %<SM:FOR>
    sprintf(' %s', char(key));
end
newline;

sharedData.atKey1=1;
guidata(f, sharedData); % <---- "add" this shared data to the figure

The next step would be that you need to have your callback be aware of the figure so that you can get the shared data. One way to do this would be to pass the figure handle as an input to the callback

KEYC = uicontrol('style','pushbutton','backgroundcolor',[1 1 1],...
    'units','normalized','position',[.15 .15 .1 .45], 'UserData', 'C',...
    'Callback',{@keypressed, f});

Note how we set the Callback property with a cell array of the callback function handle and the figure handle. You will need to do this for each control/button. The callback signature will now change too (and you will need to place the callback outside of the parent function...so it is no longer nested).

function keypressed(hObject, eventdata, hFig) %callback for key clicked
sharedData = guidata(hFig);
if strcmp(sharedData.random1{sharedData.atKey1}, get(hObject, 'UserData'))==1 %<SM:ROP>
    (msgbox('Good Job!'));
    sharedData.atKey1 = sharedData.atKey1 + 1; %<SM:RTOTAL>
    if sharedData.atKey1 > length(sharedData.random1)
        (msgbox('Good Job! You have completed the round. Start over to keep on learning!'));
    end 
else
    msgbox('ERROR. Please try again.');
end
    
end  

Note how we use guidata to get the sharedData using the handle to the figure. Try this out and see what happens!

[Han]

Yes, this worked perfectly! Thank you so much for your help!

[Han]

Actually, I am having one issue. Matlab recognizes when I click the first button and it shows a 'Good Job' message but when I go to hit the next button it says that it is incorrect (even though I know I'm pressing the right button. I made sure the function wasn't nested so I'm not sure what the issue is.

[Geoff Hayes]

Yes, I forgot a line (in the callback) to update the sharedData structure

function keypressed(hObject, eventdata, hFig) %callback for key clicked
sharedData = guidata(hFig);
if strcmp(sharedData.random1{sharedData.atKey1}, get(hObject, 'UserData'))==1 %<SM:ROP>
    (msgbox('Good Job!'));
    sharedData.atKey1 = sharedData.atKey1 + 1; %<SM:RTOTAL>
    if sharedData.atKey1 > length(sharedData.random1)
        (msgbox('Good Job! You have completed the round. Start over to keep on learning!'));
    end 
else
    msgbox('ERROR. Please try again.');
end
guidata(hFig, sharedData); % <---- need to update the sharedData structure
end  

[Han]

Thank you so much! It works now