Returning data from uibutton callback

Hi,

I want to create a script that lets me add rows to a uitable with a ui buttom. My script mostly does what I want, except that it doesn't store the inputed values when I edit the table, nor does it return the eddited table back to memory to be used later. Is anyone able to point me in the right direction?

clc
Support = [0];
Type = {false};
t = table(Support,Type);
fig = uifigure;
uit = uitable(fig,"Data",t);
btn = uibutton(fig,"Text","Add Row","Position", [400 100 100 50],"ButtonPushedFcn",@(src,event) buttonCallback(t,fig));
uit.ColumnEditable = true;


function  buttonCallback(t,fig)
Support = 0;
Type = {false};
addrow = table(Support,Type);
t = [t;addrow];
uit = uitable(fig,"Data",t);
uit.ColumnEditable = true;
btn = uibutton(fig,"Text","Add Row","Position", [400 100 100 50],"ButtonPushedFcn",@(src,event) buttonCallback(t,fig));
end

Error using matlab.internal.capability.Capability.require (line 94)
This functionality is not available on remote platforms.

Error in matlab.ui.internal.uifigureImpl (line 32)
Capability.require(Capability.WebWindow);

Error in uifigure (line 34)
window = matlab.ui.internal.uifigureImpl(varargin{:});

[Stephen23]

"Is anyone able to point me in the right direction?"

That is not how to write code for a GUI.

You are still writing linear code: first A executes, then B, then C, etc. until your script reaches the end.

But GUIs are fundamentally asynchronous code, and thinking in terms of linear code is a major hinderance to writing a GUI (i.e. you need to change how you think about code being executed). Note that in general GUI events will occur in no particular sequence. It takes a while to change how you think about code, but here are a few tips:

• write functions (not scripts).
• the GUI calls your functions (not a script calls a GUI)
• in other words: callback functions are triggered by GUI events
• share data properly within the GUI (i.e. avoid evil ASSIGNIN et al).

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

Take a look on FEX to find plenty of GUI examples which show how to perform basic actions (like reading a button status), they are often a good way to see how tasks should be achieved:

https://www.mathworks.com/matlabcentral/fileexchange?q=GUi+examples

Answer 1

[Voss]

An easy way to make the callback update the value of t is to nest the callback function inside the main function (which requires using a function - rather than a script - for the main function). Nested functions can access and modify variables in the workspaces of functions that contain them.

https://www.mathworks.com/help/matlab/matlab_prog/nested-functions.html

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html#bt9p4s2

For example, in the code below, the variable t is used in both the main_GUI function and the buttonCallback function (which is nested in main_GUI), which means the two functions' workspaces share the variable t. Therefore, when buttonCallback changes t, t is modified in both functions' workspaces (since they share the variable):

function main_GUI()

Support = 0;
Type = {false};
t = table(Support,Type);
fig = uifigure;
uit = uitable(fig,"Data",t);
btn = uibutton(fig,"Text","Add Row","Position", [400 100 100 50],"ButtonPushedFcn",@(src,event) buttonCallback());
uit.ColumnEditable = true;


    function buttonCallback()
        newSupport = 0;
        newType = {false};
        addrow = {newSupport,newType};
        uit.Data = [uit.Data; addrow]; % add a row to the uitable
        t = uit.Data; % update t
    end

end

[James Browne]

Thanks, that is close to the behavoiur I want, but I was suprised that the function it isn't passing 't' back then to memory when you call main_GUI().

the following doesn't seem to result in the updated table [t] in memory. when you call t = main_GUI().

the disp(t) functions shows that table is being updated each loop.

I can write the data to a file if I put Save("xxx") within the loop, but that isn't what I was going for, I wanted it passed back to memory. I am not sure if I need to put a save button in there to exit the 'buttoncallback' loop but when I tried to do that using the return function, that didn't seem to work.

function [t] = main_GUI()
Support = [0];
Type = {false};
t = table(Support,Type);
fig = uifigure;
uit = uitable(fig,"Data",t);
btn = uibutton(fig,"Text","Add Row","Position", [400 100 100 50],"ButtonPushedFcn",@(src,event) buttonCallback(t,fig));
uit.ColumnEditable = true;


    function  buttonCallback(t,fig)
        newSupport = 0;
        newType = {false};
        addrow = {newSupport,newType};
        uit.Data = [uit.Data; addrow]; % add a row to the uitable
        t = uit.Data; % update t
        disp(t)
    end

end

[Voss]

When main_GUI runs, as soon as it is done doing what it does, which is to create the table and the button, it returns, so the value of t returned is the initial value.

If you want main_GUI to wait before returning so that the use can interact with the table and/or button, you'll need a uiwait or waitfor command. And you'll need to decide the condition(s) for returning, e.g., have another button that says "Done" or similar whose callback sets a flag letting the program know the user is ready for main_GUI to return.

[Stephen23]

@James Browne: you can use WAITFOR:

https://www.mathworks.com/help/matlab/ref/waitfor.html

For example, at the end of your main GUI code:

waitfor(fig)

The function (and your data) then returns when the figure is deleted. This is a simple, efficient, and reliable approach to including an asynchronous GUI within some linear code.