do not work ishandle and ishghandle in a loop?

Question

Carlos Molina 2020-3-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/512067-do-not-work-ishandle-and-ishghandle-in-a-loop

编辑： Stephen23 2020-3-21

Hello all,

I have a program which read values from sensors. The program must stop reading when the figure is closed. I had a program where I used a callback linked to the serial to execute when a terminator was received, then I evaluated the contition of ishghandle and worked properly.

Now, I would like to have the reading code inside of a loop, which execution condition is ishghandle. Well, it seems that this function or ishandle do not work inside of a loop, because value once figure is executed is 1 and it does not change to 0 when the figure is closed. I tested placing the condition in the while or inside the while as below.

My version is 2018b

function read(a)
figure;
drawnow;
delete(instrfindall);
s = serial(a);
fopen(s);
p=ishandle(gcf);
while(1)
   
    if p == 1
        n = s.BytesAvailable;
        if n == 6
            m = fread(s,6);
            disp(m);
            disp(p);
        end
        p=ishandle(gcf);
    else
        break;
    end
end
fclose(s);
end

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Answer 1

Walter Roberson 2020-3-21

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/512067-do-not-work-ishandle-and-ishghandle-in-a-loop#answer_421211

在 MATLAB Online 中打开

If there is no current figure, then gcf will create a new figure... which would have a valid handle.

function read(a)
fig = figure;
drawnow;
delete(instrfindall);
s = serial(a);
fopen(s);
p=ishandle(fig);
while(1)
   
    if p == 1
        n = s.BytesAvailable;
        if n == 6
            m = fread(s,6);
            disp(m);
            disp(p);
        end
        p=ishandle(fig);
    else
        break;
    end
end
fclose(s);
end