如何在 App Designer 中停止我的网络摄像头循环？ Matlab

Question

I'm doing an interface in app designer where I turn on my webcam when I press a button(Empezar button), the only problem is that I can't find a way on how to stop my webcam, It's on a loop and I need to finish that loop when I press another button (stop button), but I've tried a lot of things and nothing really seems to work, I tried with a buttonpressfcn didn't work, opening a figure and when it closes the figure the vid stops didn't work either, any ideas? I know how to stop the vid in GUIDE but I have to use App Designer and It's not the same I think:(

    properties (Access = public)
        UIFigure       matlab.ui.Figure
        StopButton     matlab.ui.control.Button
        EmpezarButton  matlab.ui.control.Button
        UIAxes         matlab.ui.control.UIAxes
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: EmpezarButton
        function EmpezarButtonPushed(app, event)
%         clear all;
            
        
            
            micamara=webcam(1);
            micamara.Resolution='640x360';
            micamara.Brightness=10;
            %ventana=app.StopButton.ButtonPushedFcn;
            %while ishandle(ventana)
            ventana=figure;
             while ishandle(ventana)
               img=snapshot(micamara);
               imshow(img,'Parent',app.UIAxes);
               
                
            end
            
        end

        % Button pushed function: StopButton
        function StopButtonPushed(app, event)
            global ventana;
             ventana=1;
        end
    end

Answer 1

Hey engineerinprocess (aren't we all..?)

The infinite loop in your EmpezarButtonPushed callback makes it impossible for Matlab to handle other callbacks, like your StopButtonPushed callback. That's way it does not work.

The proper way of solving this would be using a timer.

• The setup-code I would move to the 'startupFcn' of your app, and be sure to store the micamera as a property of your app. You'll need it later. In the startupFcn you also initialize a timer with a certain period.
• A timerFcn callback can then do the things you have in your while loop.
• The EmpazarButtonPushed now starts the timer (if not already running)
• The StopButtonPushed callback should stop the timer (if running).

You should also add a CloseRequestFcn callback for your figure, where you stop and delete your timer object. Another thing I usually do during development, EngineerInProcess, is to put the contents of the timer callback in a try/catch block, where in the catch block I display the error message and stop the timer.

There is actually an example in the appdesigner on how to use timers in apps. You may want to check that out as well.