State button callback- break while loop?

Question

Veena Chatti 2020-9-3

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/588499-state-button-callback-break-while-loop

评论： Veena Chatti 2020-9-12

Hi,

I'm trying to loop through hundreds of frames in a file with the push of a state button and the use of a slider in AppDesigner. With the code below, what I've managed so far is to get it to loop until the end of all frames and then stop.

What I'd like it to do further, however, is to loop continuously until the button is pressed, and stop looping by breaking the while loop when the button is un-pressed.

I would greatly appreciate all your tips and suggestions!

Thanks!

    v = app.pswitch.Value;
    switch v
        case 0
        %                     do nothing
        case 1
            j = get(app.Slider, 'Value');
            while j < 300 % (number of frames)
                if v == 1
        %                             do this:
                    pause(1/1000)
                    j = get(app.Slider, 'Value');
                    app.Spinner.Value = j+1; % go to the next frame
                    app.Slider.Value = j+1; % go to the next frame
                    app.I = imshow(app.testrgb(:,:,3,j+1), [300 1300],...
                        'Parent', app.UIAxes); % display the next frame
                end
            end
            app.Spinner.Value = 1;
            app.Slider.Value = 1;
            set(app.pswitch, 'Value', 0)
            
        otherwise
        %                     do nothing
    end
    
    

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Rik 2020-9-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/588499-state-button-callback-break-while-loop#answer_489208

In general the solution to this is to use a flag that is controlled by your button. Then inside the while loop you check for that flag (a simple if flag,break,end will do).

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Veena Chatti 2020-9-3

Thanks, I'd like to try this. Where can I find some tips about how to use a flag and have it under the control of the button?

请先登录，再进行评论。

Answer 2

Mohammad Sami 2020-9-3

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/588499-state-button-callback-break-while-loop#answer_489229

在 MATLAB Online 中打开

You can try something like this.

app.STOPButton.Enable = true;
app.STOPButton.Value = 0;
while(somecondition)
    % do something
    if(app.STOPButton.Value == 1)
        break;
    end
end
app.STOPButton.Enable = false;
app.STOPButton.Value = 0;

6 个评论
显示 4更早的评论隐藏 4更早的评论

Veena Chatti 2020-9-3

在 MATLAB Online 中打开

Thanks, Mohammad and Rik! Yes, I am using a state button.

Setting a flag under the control of the button and using drawnow worked well. I also think your code would have worked, Mohammad, with drawnow.

Here's the functional code that I decided to use, in case anyone trying to do something similar comes across this thread:

value = app.pswitch.Value;
j = get(app.Spinner, 'Value');
set(app.pswitch, 'Text', 'Pause');
flag = 1; % Set flag
while(flag) && j < 299
    
    pause(1/1000)
    
    j = get(app.Spinner, 'Value');
    set(app.Spinner, 'Value', j+1);
    set(app.Slider, 'Value', j+1);
    
    app.I = imshow(app.testrgb(:,:,3,j+1), [300 1300],...
        'Parent', app.UIAxes); % Display command
    
    drawnow; % get it to check 
    f = get(app.pswitch,'Value');
    
    if isequal(f, 0)
        set(app.pswitch, 'Text', 'Play');
        flag = 0; 
        break;
    elseif ~isequal(f,1)
        set(app.pswitch, 'Text', 'Pause');
    end
end

This is a bit off topic, but do either of you (or anyone else who sees this) know the smallest time interval and resolution it's possible to set with pause()?

Rik 2020-9-3

The theoretical limit would be eps. As a practical limit I would suggest 30ms.

It isn't hard to test this, just use a loop to make the time smaller until tic,toc is telling you the pause is much longer than the time you asked for. I you want I can write some code for you. I'm currently on mobile so writing an example is more challenging.

Veena Chatti 2020-9-12