MATLAB: Use global variable in another GUI.

global variableMATLAB

Hello! I´ve created a global variable in a main GUI. A buttom on this opens a second GUI where I need to use the global variable. Must I declare:

global MyVariable;

in every function where I will use MyVariable inside the second GUI? Or there is a way to declare it once?

Best Answer

You have to declare a variable as global in each function you want to use it, of course. Otherwise it would be easy to let Matlab crash massively by declaring any frequently used variables like "x" or "K" globally as global.

It is explained in the documentation clearly, how globals are used. Therefore a

doc global

would help already.

Note that global variables are known to cause troubles and impede the debugging. Clean code does not contain any global variables for this reason. Better store the data in a figure and share its data using e.g. the ApplicationData.

Related Solutions

MATLAB: GUI. Handle variable.

Your use of guidata is perfect: calling it at the end of a callback function lets you save the handles structure, together with any new data that you have added to handles. Then this data is available to all of the other callback functions.

I have no idea what actions will trigger these callbacks, so you will need to check that the callback functions are actually being run. Note that using variable/fieldnames that only differ by case is not recommended: instead of x1 and X1 you should use more descriptive names, e.g. x1Obj and x1Num.

You have mixed up the allocation within startDisplay_Callback, you will actually need to allocate the values in handles to the variables that you want to plot, like this:

xOne = handles.x1Num;
yOne = handles.y1Num;
...
plot([xOne, xTwo],[yOne,yTwo]);

MATLAB: Issue with GUI.

Justin - I think what you can do is create another timer to periodically update the status bar, rather than relying a while loop that is called from within a hidden button (your pushbutton8).

For example, in the GuiTImerUpdateTextExample_OpeningFcn, you can instantiate your two timers, the original one and one for your progress bar as

 handles.timerQuery = timer('Name','MyQueryTimer',               ...
                            'Period',3,                     ...
                            'StartDelay',1,                 ...
                            'TasksToExecute',inf,           ... 
                            'ExecutionMode','fixedSpacing', ...
                            'TimerFcn',{@timerQueryCallback,hObject}); 
 handles.timerProgress = timer('Name','MyProgressTimer',        ...
                               'Period', 0.01,                   ...
                               'TasksToExecute',inf,            ...
                               'ExecutionMode', 'fixedSpacing', ...
                               'TimerFcn', {@timerProgressCallback, hObject});

The "query timer" will expire after three seconds, corresponding to the query that is asked of the user. The "progress timer* will expire every 10 milliseconds and will call the timerProgressCallback. Once we have created the timers, we can initialize your progress axes as

 % set the axes
 cla(handles.axes1);
 set(handles.axes1,'Visible','on','color',[.9 .85 .3]); %this will set the color of the patch
 axis(handles.axes1,[0,1,0,1]); %show only from x=0to 1 and y=0to1
 handles.hPatch = patch([0,0,0,0],[0,0,1,1],'g');
 axis(handles.axes1, 'off'); %do not show axis bars

Note how we create the patch and save its handle to the handles structure. We do this so that we can update this patch object rather than creating a new one every time we want to update the progress "bar".

We then save the updated handles structure and start the the query timer as

 guidata(hObject, handles);
 start(handles.timerQuery);

We don't start the other timer as we rely on the timerQueryCallback to do this for us as

 function timerQueryCallback(hTimer, eventdata, hFigure)
 handles = guidata(hFigure);
 % stop the progress timer
 stop(handles.timerProgress);
 % only set the progress timer to complete if there is text in pushbutton1
 % we pause for half a second to allow the progress bar to update
 if ~isempty(get(handles.pushbutton1,'String'))
    set(handles.hPatch,'XData',[0 1 1 0]);
    pause(0.5);
 end
 % etc.
 % reset the patch to show zero progress
 set(handles.hPatch,'XData',[0 0 0 0]);
 % use tic so that we can correctly update the progress
 tic;
 % start the timer
 start(handles.timerProgress);

That just leaves the timerProgressCallback which can be defined as

 function timerProgressCallback(hObject, eventdata, hFigure)
 handles = guidata(hFigure); 
 if ~isempty(handles)
    periodQuery    = get(handles.timerQuery,'Period');
    percentComplete = double(toc)/periodQuery;
    set(handles.hPatch,'XData',[0 percentComplete percentComplete 0]);
 end

We use toc and the period of the query timer to determine the progress and so how much of the patch to draw.

Try the above and see what happens! (See the attached for a working example.)

Best Answer

Related Solutions

MATLAB: GUI. Handle variable.

MATLAB: Issue with GUI.

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