How to stop a while loop using a GUI pushbutton?

I have a while loop and I have a STOP pushbutton that breaks the loop. Basically I want to break the loop using the pushbutton instead of typing CTRL+C on command window. I tried the return clause but it didn't work and the break clause aparently it's used inside the loop (which isn't the case).

Can anyone help me?

Thanks!

Answer 1

[Walter Roberson]

while true
  drawnow()
  stop_state = get(YourPushbuttonHandle, 'Value');
  if stop_state
    break;
  end
  ...
end

[Flávio]

It doesnt seem to work. What do i write in the pushbutton callbackfunction? The thing is, i have a pushbutton 1 that runs my code with the while loop. Then i have a pushbutton 2 that stops the loop. What do i put in button2 callback? I tried your code but nothing happens when i hit button2.

Thanks!

[ZacksHacks]

Some people might find it crude, but you can just use a global variable if you are not familiar with GUI syntax and just want a quick fix.

%Button 1 Click

global true;

true = 1;

while true == 1

drawnow()

%Your loop code here

end

%Stop Button Click

global true;

true = 0;

[Vibhor Gulati]

Oh you saviour! Nothing else seemed to work for me.

[Jannis]

Super helpful, also works in appdesign.

[Stephen23]

It is recommended to avoid slow and buggy global variables:

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

[Image Analyst]

App Designer has a different way of using global variables I believe - you don't use the global keyword.

[Stephen23]

@Image Analyst: I have never used App Designer, but as far as I can tell it creates some kind of objects, whose properties are available throughout the app:

https://www.mathworks.com/help/matlab/creating_guis/share-data-across-callbacks-in-app-designer.html

What does this have to do with global variables?

Answer 2

[Image Analyst]

See my attached little demo. It counts when you click the Go button and stops counting when you click the Stop button.

[Liza Vörös]

It does not work

[Liza Vörös]

I get this error:

Dot indexing is not supported for variables of this type.

Error in gostop>btnStop_Callback (line 103)
set(handles.btnStop,'userdata',1)
Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in gostop (line 45)
    gui_mainfcn(gui_State, varargin{:});
Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)gostop('btnStop_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating UIControl Callback.
Dot indexing is not supported for variables of this type.
Error in gostop>btnGo_Callback (line 84)
set(handles.btnStop, 'userdata', 0);
Error in gui_mainfcn (line 95)
        feval(varargin{:});
Error in gostop (line 45)
    gui_mainfcn(gui_State, varargin{:});
Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)gostop('btnGo_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating UIControl Callback.

[Image Analyst]

I just downloaded it again and it works fine. When it says "Dot indexing is not supported" for the handles variable, it indicates to me that somehow your handles structure got corrupted. Did you modify my file at all? Like put a clear statement in there somewhere? Please attach your exact files and I'll download and run your version.

[Haotian Xue]

It works great, thank you so much.

[aung lin]

Thank You very much Sir!

Answer 3

[Birkan GOCERLER]

Use toggle button http://blogs.mathworks.com/videos/2010/12/03/how-to-loop-until-a-button-is-pushed-in-matlab/

Answer 4

[Andrew Davies]

The solution to the problem can be found here http://stackoverflow.com/questions/4522447/breaking-from-for-loop-in-matlab-gui

the basic outline could look like this:

For the callback of the start push button you want something like this.

 functionpushbutton1_Callback(hObject, eventdata, handles)
handles.stop_now = 0; %Create stop_now in the handles structure
guidata(hObject,handles);  %Update the GUI data
while ~(handles.stop_now)

    yourfunction()

    drawnow %Give the button callback a chance to interrupt the              %opening fucntion

    handles = guidata(hObject);  %Get the newest GUI data
end

In the callback for the stop button you want

    function pushbutton2_Callback(hObject, eventdata, handles)
         handles.stop_now = 1;
         guidata(hObject, handles); % Update handles structure

Answer 5

[Greig]

Essentially of the these solutions are based on the same ideas. Another approach (that uses the same idea) is to use the MATLAB inbuilt waitbar() function, which supports canceling a loop and details how to do in the documentation... FOUND HERE. This way you don't have to explicitly program the canceling functionality of your button 2, which is useful if you are still getting to grips with GUIs.

Edit: And only after answering do I realize this is a somewhat old thread!

Answer 6

[Seo-Hyun]

I used a toggle button for pause, and added the pause code in the loop. While pausing, you can always grab a breakpoint in the paused line and continue debug. Try this.

while(1)

      if handles.pause.Value
        pause(1);
        handles.pause.String = 'Resume';
        disp('waiting');
        while ~handles.pause.Value
            handles.pause.String = 'Pause';            
            break;
        end

          continue;
      end

end

function pause_Callback(hObject, eventdata, handles)