Break a while loop in a GUI Pushbutton

Hi there,

I have a GUI set up and it has a Start pushbutton and a Stop pushbutton. Upon pushing the start, data is transmitted and received between AVR and matlab with Serial communication.

What I am trying to do is while the data is communicated and being run, if the stop button is pressed, the while operation should stop. This should be accomplished if I can just break the while loop, but the code that I've tried using 'assignin' and 'evalin' hasn't succeeded. Actually it occasionally works but sometimes doesn't work. Here is what my code :

function StartButton_Callback(hObject, eventdata, handles)
flag = 0;
assignin('base','flag', flag);
bt = Bluetooth('JCNET-BT-7827',1);
fopen(bt);
while 1
    %%Receiving and Display Serial Communication
    flag = evalin('base', 'flag');
    if flag == 1
        break;
    end
end

When the EndButton is pressed,

% --- Executes on button press in EndButton.
function EndButton_Callback(hObject, eventdata, handles)
flag = 1;
assignin('base','flag', flag);

Could anyone give me for advices? Thanks a lot in advance!

Answer 1

[Robert U]

Hi MINKYUNG KIM,

below you find an example for breaking a while loop within a pushbutton controlled GUI. The data exchange is done using guidata. Avoid assignin and evalin if possible. These methods are silly to debug and prone to errors.

function GuiBreak

    GUI.fh = figure;
    
    GUI.h1 = uicontrol('style','Edit',...
                   'string','XX',...
                   'Units','normalized',...
                   'Position',[0.1 0.1 0.8 0.2],...
                   'backgroundcolor','c',...
                   'Tag','EditField2',...
                   'Enable','off');
    
    GUI.h2 = uicontrol('Style','PushButton',...
                   'String','Start',...
                   'Units','normalized',...
                   'Position',[0.1 0.4 0.3 0.2],...
                   'callback',{@func_compute},...
                   'Tag','StartButton',...
                   'backgroundcolor',...
                   'g','FontSize',12);
                   
    GUI.h3 = uicontrol('Style','PushButton',...
                   'String','Stop',...
                   'Units','normalized',...
                   'Position',[0.5 0.4 0.3 0.2],...
                   'callback',{@breakOP},...
                   'Tag','StopButton',...
                   'backgroundcolor',...
                   'r','FontSize',12);
    
    myHandle = guihandles(GUI.fh);  % save gui handles to struct
    myHandle.breakOP = false;       % flag for break OP
    guidata(GUI.fh,myHandle);       % save structure
end

function func_compute(~,~)
    
    a = 1;
    while 1
        myHandle = guidata(gcbo);                   % get structure
        myHandle.EditField2.String = num2str(a);    % edit field string
        pause(0.01);
        if myHandle.breakOP                         % check for break OP flag
            break;
        end
        a = a +1;
    end
   
end

function breakOP(~,~)
    myHandle = guidata(gcbo);   % get structure
    myHandle.breakOP = true;    % change break OP flag
    guidata(gcbo,myHandle);     % save structure
end

Kind regards,

Robert

[Robert U]

If you want to have continous operation you can provide a flag reset to the start button callback function:

function GuiBreak


    GUI.fh = figure;
    
    GUI.h1 = uicontrol('style','Edit',...
                   'string','XX',...
                   'Units','normalized',...
                   'Position',[0.1 0.1 0.8 0.2],...
                   'backgroundcolor','c',...
                   'Tag','EditField2',...
                   'Enable','off');
    
    GUI.h2 = uicontrol('Style','PushButton',...
                   'String','Start',...
                   'Units','normalized',...
                   'Position',[0.1 0.4 0.3 0.2],...
                   'callback',{@func_compute},...
                   'Tag','StartButton',...
                   'backgroundcolor',...
                   'g','FontSize',12);
                   
    GUI.h3 = uicontrol('Style','PushButton',...
                   'String','Stop',...
                   'Units','normalized',...
                   'Position',[0.5 0.4 0.3 0.2],...
                   'callback',{@breakOP},...
                   'Tag','StopButton',...
                   'backgroundcolor',...
                   'r','FontSize',12);
    
    myHandle = guihandles(GUI.fh);  % save gui handles to struct
    myHandle.breakOP = false;       % flag for break OP
    guidata(GUI.fh,myHandle);       % save structure
end

function func_compute(~,~)
    myHandle = guidata(gcbo);
    myHandle.breakOP = false;   % flag for break OP
    guidata(gcbo,myHandle);     % save structure
    
    if ~isempty(str2num(myHandle.EditField2.String))
        a = str2num(myHandle.EditField2.String);
    else
        a = 1;
    end
    
    while 1
        myHandle = guidata(gcbo);                   % get structure
        myHandle.EditField2.String = num2str(a);    % edit field string
        pause(0.01);
        if myHandle.breakOP                         % check for break OP flag
            break;
        end
        a = a +1;
    end
    
end

function breakOP(~,~)
    myHandle = guidata(gcbo);   % get structure
    myHandle.breakOP = true;    % change break OP flag
    guidata(gcbo,myHandle);     % save structure
end