set() function works on 2017a but crash on 2018b

Question

Jenny Khuon 2020-6-10

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/545891-set-function-works-on-2017a-but-crash-on-2018b

评论： Adam Danz 2020-6-15

The following codes works on 2017a, but failed on 2018b I use debugger step by step, and found out it crashes at set(axs,'Parent',p); on version 2018b.

On version 2018b at line set(axs,'Parent',p); it will call the program usejava.m, but not 2017a.

p=uipanel(gcf,'Units','normalized','Position',...

[0 0.2 10.8],'BorderType','none','Tag','CursorPanel1');

set(p,'BackgroundColor',get(gcf,'Color'));

axs=findall(gcf,'Type','Axes');

set(axs,'Parent',p); <== crashes on this line on version 2018b, but it works on version2017a

Please help.

Thank you.

I have Matlab license.

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Jenny Khuon 2020-6-10

I add try/catch ME, and it works. It display chart and table as I expected.

But I cannot submit the code to my customer, with no (blank) statement in catch ME block. It will be a big joke.

try
    p=uipanel(gcf,'Units','normalized','Position',...
        [0 0.2 1 0.8],'BorderType','none','Tag','CursorPanel1');        
    set(p,'BackgroundColor',get(gcf,'Color'));
   axs=findall(gcf,'Type','Axes');  
   set(axs,'Parent',p);
catch ME
   *** blank, no statement here. ***
end

Jenny Khuon 2020-6-10

I need to use gcf. I did try without gcf, gca, gcbo, it could not run at all. Please see the message I just sent.

axs is:

3×1 graphics array:

Axes (Endurance Test I)

Axes

AxesToolbar

Although I can add a try/catch ME block, and I can get what I expected. But, I need to shutdonw the matlab, and re-launch again. Otherwise, it will crash the second time I run it again.

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Answer 1

Adam Danz 2020-6-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/545891-set-function-works-on-2017a-but-crash-on-2018b#answer_449366

编辑：Adam Danz 2020-6-10

First, some feedback,

The try-catch may have avoided an error message but that doesn't mean the problem was solved. The problematic line very likely still does not work and will just invoke the 'catch' code.

You don't need to use gcf. You need to use the actual figure handle or you can search for the figure handle. The (big) problem with gcf that Stephen Cobeldick pointed out is that you have no control over which figure it actually references. If more than 1 figure is available, even if it's a hidden figure, the user might click on a different figure and suddenly the rest of the code will be pointless. If the original figure is somehow deleted, gcf will create a new figure but in that case, you would want an error indicating an invalid figure handle.

Cause of the problem & the solution

"axis is a 3x1 graphics array".

Note that the 3rd element is not an axes, it's an AxisToolbar.

When you call set(axs,'Parent',p), it tries to see the parent of all 3 objects as p. As the error message indicates, "AxesToolbar cannot be a child of Panel.". To set the parent of the 2 axes,

set(axs(1:2),'Parent',p)

It's unclear why the axistoolbar is being identified in the call to findall(gcf,'Type','Axes');

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Adam Danz 2020-6-10

编辑：Adam Danz 2020-6-10

Jenny, I believe you that the error message is thrown by the set() command. But I don't think the set command is the problem. I think the inputs to the set command is the problem and the inputs are created by the findall() command. That doesn't mean the findall() command would throw an error. Errors can happen without an error message. Here's an example.

% I want to add 2 + 3 but I accidentally wrote 3 as a character. 
x = 2 + '3'
ans
x =
    53   % no error message but the output is bogus

Matlab is moving away from using Java. They often change their backend between releases and virtually none of that is documented and I'm not an employee of Mathworks.

"It crashes" doesn't give us much information. I'm assuming you got the same exact error message you shared earlier

Error using matlab.graphics.primitive.world.Group/set
AxesToolbar cannot be a child of Panel.
Error in showData (line 48)
                 set(axs,'Parent',p);
Error in xxx/ShowDataTimeSummary (line 186)
            showData('init') % throw error here
 Error while evaluating ToggleTool ClickedCallback.

That error should happen if you try to set the Parent property of an AxesToolbar to a Panel object.

The real question is, why is an AxesToolbar identified by the findall(gcf,'Type','Axes') command. That shouldn't happen and I can't make any other suggestions without seeing your code and reproducing the problem. If you can share a reasonably sized example that reproduces the problem in any version of Matlab, I can look into it further.

Steven Lord 2020-6-11

I commented out all of the code in usejava.m, I even could not load the testing data at the very beginning of the process. In the usejava.m contains a code isok = system_dependent('useJava',feature);, the feature is awt. By the way, I could not find system_dependent in Matlab documentation, could you ?

I strongly recommend that you not modify MathWorks-provided functions. Doing so could cause other MathWorks functions to stop working correctly or at all. [To answer the other part of your question system_dependent is an undocumented function. You shouldn't use it in your code unless MathWorks Technical Support tell you to use it to work around a specific problem or to diagnose a problem.]

I agree with Adam Danz. The problem seems to be that you're trying to parent an object to a panel that cannot be parented to a panel. It is NOT a problem with the set function, the findall function, or the usejava function.

Rather than using findall there are a couple alternate approaches I recommend you try.

Create your panel first, and parent your axes to the panel as you create them.

P = uipanel;
ax = axes('Parent', P);

As you create your axes store their handles in a vector. You can use the gobjects function to preallocate this vector of handles. After you create your panel, pass this vector of handles (removing any placeholder objects that still remain in it, if you preallocated a larger vector than you actually needed) into set.

axlist = gobjects(1, 4);
for whichPlot = 1:4
    axlist(whichPlot) = subplot(2, 2, whichPlot);
end
P = uipanel;
set(axlist, 'Parent', P)

Use findobj instead of findall. findall finds objects whose handles have their Handle Visibility property set to 'off' while findobj doesn't.

Jenny Khuon 2020-6-15

For 2017a:

ax=findall(f,'Type','Axes');

For 2018b:

ax=findall(f,'Type','axes');

I have tested on 2017a, either Axes or axes is working.

But, for 2018a, it only accepts axes.

Hope this help.

Adam Danz 2020-6-15

That's not correct. Here's the results for both upper and lower case "axes" in r2018a..

% Lower case
>> ax=findall(gcf,'Type','axes')
ax = 
  Axes with properties:
             XLim: [0 1]
             YLim: [0 1]
           XScale: 'linear'
           YScale: 'linear'
    GridLineStyle: '-'
         Position: [0.13 0.11 0.775 0.815]
            Units: 'normalized'
  Show all properties
  
% Upper case
>> ax=findall(gcf,'Type','Axes')
ax = 
  Axes with properties:
             XLim: [0 1]
             YLim: [0 1]
           XScale: 'linear'
           YScale: 'linear'
    GridLineStyle: '-'
         Position: [0.13 0.11 0.775 0.815]
            Units: 'normalized'
  Show all properties
  
% Show version number
>> ver
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.4.0.813654 (R2018a)  % <-----
MATLAB License Number: xxxxxx
Operating System: Microsoft Windows 7 Professional  Version 6.1 (Build 7601: Service Pack 1)
Java Version: Java 1.8.0_144-b01 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
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