Why does my uicontextmenu only show after a pause/breakpoint?

Question

Cyrano Chatziantoniou 2023-1-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1899590-why-does-my-uicontextmenu-only-show-after-a-pause-breakpoint

回答： Jan 2023-1-24

I'm trying to show a contextmenu in a uifigure ontop of some uiaxes. On a mouseclick event, the function below is called to display the contextmenu.

This code runs fine, but when I remove the pause, the contextmenu stops showing. The location also seems to matter, if I put the pause any earlier in the code, no contextmenu shows up. Why is this happening? Are there any race-conditions I should be aware of?

function UOContextMenu(app, id, pos)
            %Creates a contextmenu where the user clicked
            %Input: 
            %   app - the app
            %   id  - id of the userobject
            %   pos - cursor position
            %Find axis
            axID    = GUI.FindAxisAtPosition(app, pos);
            axis    = app.GetAxis(axID);
            
            cm = uicontextmenu(app.UIFigure);
            
            m1 = uimenu(cm,'Text','Delete');
            m2 = uimenu(cm,'Text','Rename');
            m3 = uimenu(cm,'Text','Copy To');
            m4 = uimenu(cm,'Text','Toggle Visibility');
            pause(0.1)
            
            cm.Position   = [pos(1), pos(2)];
            cm.Visible    = 'on';
            axis.ContextMenu = cm;
           
           return
           
         

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Answer 1

Jan 2023-1-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1899590-why-does-my-uicontextmenu-only-show-after-a-pause-breakpoint#answer_1155125

Try to replace pause by drawnow. This allows the GUI to activate the updated properties. If this is working also, this is the expected and documented behavior. See: drawnow .