Problem with variable not being global in creating GUI

Question

RIshabh Golchha 2016-1-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/262945-problem-with-variable-not-being-global-in-creating-gui

评论： Walter Roberson 2016-1-7

simple_gui_4.m

I am exploring MATLAB GUI by writing code rather than GUIDE.

Attached is the code. What I want is that is my test_value text box should have access to handles.latitude once it is updated. For Checking this I set it such that when i type anything in it, it just should show me the latitude value. But it isnt.

Error being shown is

Error using simple_gui_4/test_output_Callback (line 40) Not enough input arguments.

Error while evaluating UIControl Callback

Can someone please help me?

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Sivakumaran Chandrasekaran 2016-1-7

when i run this code, i get error on line no.28.. movegui command is not supporting structure it seems

RIshabh Golchha 2016-1-7

It doesn't show any error for me. Maybe different versions of Matlab. Anyways you can just comment it out as it is not the primary thing

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Answer 1

Walter Roberson 2016-1-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/262945-problem-with-variable-not-being-global-in-creating-gui#answer_205380

编辑：Walter Roberson 2016-1-7

在 MATLAB Online 中打开

    function latitude_Callback(hObject,eventdata)
        handles = guidata(hObject);
        handles.latitude = get(hObject,'String');
        display(handles.latitude); 
        guidata(hObject,handles)
    end
    function test_output_Callback(hObject,eventdata)
        handles = guidata(hObject);
        set(findobj('Tag','test_value'),'String', handles.latitude)
    end

The fundamental problem you had is that handles is not automatically passed to functions by MATLAB. handles is a GUIDE construct, and GUIDE has to go through trouble to maintain it so that routines always get the current value.

You are using nested functions so you would have been better off avoiding the traditional handles, such as

function simple_gui_4
    %define variables used in nested functions
    lattitude_string = '';
    %define figure and controls
    f = figure('Visible','off','Position',[100,100,1000,500]);
    hcity = uicontrol('Style','popupmenu',...
             'String',{'Delhi','Mumbai','Visakhapatnam'},...
             'Position',[150,475,100,25],...
             'Callback',{@popup_menu_Callback});
    hlatitude = uicontrol('Style','edit',...
              'Position',[150,450,100,25],...
              'Callback',{@latitude_Callback});
    hlatitude_label = uicontrol('Style','edit',...
              'String','Latitude',...
              'Position',[50,450,100,25],...
              'BackgroundColor',[1 1 1]);
    htest_output = uicontrol('Style','edit',...
              'String','test',...
              'Tag','test_value',...
              'Position',[150,50,100,25],...
              'Callback',{@test_output_Callback});
    % Assign a name to appear in the window title.
    f.Name = 'Simple GUI';
    % Move the window to the center of the screen.
    movegui(f,'center')
    % Make the UI visible.
    f.Visible = 'on';
    function latitude_Callback(hObject,eventdata)
      %nested function
      %set variable that was defined in outer function
      latitude_string = get(hObject,'String');
      disp(latitude_string); 
    end
    function test_output_Callback(hObject,eventdata)
      %nested function
      %uses variables defined in outer function
      set(htest_output,'String',latitude_string)
    end
end

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RIshabh Golchha 2016-1-7

The first one you gave works. But the second one is giving similar error as test_output_Callback doesn't have access to the updated latitude_string

Walter Roberson 2016-1-7

在 MATLAB Online 中打开

simple_gui_4.m

It works for me once I change your f.Name and f.Visible references to the older syntax (I am using R2014a.) This is, incidentally, why Sivakumaran encountered the problem with movegui -- they must be using an older MATLAB.

set(f, 'Name', 'Simple GUI')
set(f, 'Visible', 'on')

If you are using R2014a or earlier then those changes need to be made, but for R2014b or later the syntax you used looks like it would work.

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Answer 2

Stalin Samuel 2016-1-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/262945-problem-with-variable-not-being-global-in-creating-gui#answer_205381

编辑：Stalin Samuel 2016-1-7

在 MATLAB Online 中打开

function simple_gui_4
f = figure('Visible','on','Position',[100,100,1000,500],'Name','Simple GUI');
set(f ,'Units','Pixels','Position',get(0,'ScreenSize'))
     f.hcity = uicontrol('Style','popupmenu',...
             'String',{'Delhi','Mumbai','Visakhapatnam'},...
             'Position',[150,475,100,25],...
             'Callback',{@popup_menu_Callback});
      f.hlatitude = uicontrol('Style','edit',...
              'Position',[150,450,100,25],...
              'Callback',{@latitude_Callback});
      f.hlatitude_label = uicontrol('Style','edit',...
              'String','Latitude',...
              'Position',[50,450,100,25],...
              'BackgroundColor',[1 1 1]);
      f.htest_output = uicontrol('Style','edit',...
              'String','test',...
              'Tag','test_value',...
              'Position',[150,50,100,25],...
              'Callback',{@test_output_Callback});
  %        
% Make the UI visible.
% f.Visible = 'on';
    function latitude_Callback(hObject,eventdata,handles)
        handles.latitude = get(hObject,'String');
        display(handles.latitude); 
        guidata(hObject,handles)
    end
      function test_output_Callback(hObject,eventdata,handles)
          set(findobj('Tag','test_value'),'String',handles.latitude)
      end
      function popup_menu_Callback(hObject,eventdata,handles)
          msgbox('popup executed')%replace with your code
      end
  end