GUI. Handle variable.

Hi. Is this the right way to retrieve a variable from handle? I read the documentation and examples but still didn't manage to make it work. Pls, give me a hint whats wrong. Learning to use guide I'm trying to draw a line between 2 points inputted in the textbox.

Thanks.

function x1_Callback(hObject, eventdata, handles)
handles.X1=str2double(get(handles.x1,'string'));
guidata(hObject,handles); 

function y1_Callback(hObject, eventdata, handles)
 handles.Y1=str2double(get(handles.y1,'string'));
guidata(hObject,handles); 

function x2_Callback(hObject, eventdata, handles)
handles.X2=str2double(get(handles.x2,'string'));
guidata(hObject,handles);

function y2_Callback(hObject, eventdata, handles)
handles.Y2=str2double(get(handles.y2,'string'));
guidata(hObject,handles);

function startDisplay_Callback(hObject, eventdata, handles)
handles.X1=xOne; 
handles.Y1=yOne;
handles.X2=xTwo;
handles.Y2=yTwo;
plot([xOne, xTwo],[yOne,yTwo]);

Answer 1

[Stephen23]

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]);

[Iryna Kovalenko]

@Stephen Cobeldick

I changed the allocation, thank you. There no if or other conditions which will trigger the callbacks. The code I posted is the full version, except for the .fig file. There I have text boxes(with the tags x1,y1 etc.) with numbers and button "startDisplay". When I press it I want to get a line, but it doesn't appear. That's is the issue. If the rest of the code is ok, how to get the line ?

[Stephen23]

You will need to set the button's callback function to call whichever function you want it to call, something like this:

but_handle = uicontrol(fig_handle, 'Style','pushbutton', ... ,'Callback',@startDisplay_Callback);

Note that this can only call one function. One graphics event (e.g. clicking a button) can trigger one callback function to get called, but it is up to the designer to specify which one.

https://www.mathworks.com/help/matlab/creating_plots/callback-definition.html

https://www.mathworks.com/help/matlab/creating_guis/write-callbacks-using-the-programmatic-workflow.html

You appear to only have one button... but you have five callback functions... it is not clear to me how you want to call the other functions.

[Arooba Khalid]

@Stephen Cobeldick hi, I’m collaborating on this with her and We have assigned all the 4 textboxes to their callback, but we want to call these variables in our push buttons.For example, after i assigned these variables in their callback when i go to a pushbutton i need to use the get function again, its not automatically using the variables

[Stephen23]

@Arooba Khalid: Using a callback with a uicontrol edit box (I doubt that you are using a text box) is possible, but probably not worth the bother (unless you specifically want to trigger an action that is caused by someone entering some text). If there is a button that starts a calculation then personally I would just get all the required String properties when that button is pressed (rather than using callbacks for each edit box), as this would be simpler to implement, easier to understand, and easier to debug. All of the edit box handles are available in handles, so it is quite straightforward to get the String property for each edit box.