Drop Down Menu App Designer Values

Question

Nick M. 2019-3-1

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https://ww2.mathworks.cn/matlabcentral/answers/447641-drop-down-menu-app-designer-values

编辑： Sven 2019-3-1

Hi, I am having an issue where the app designer GUI does not detect the default value in the drop down menu to hide something specific. For example, if the default value in the drop down menu is Option 1, the field is not hidden unless I select another Option such as Option 2 and reclick Option 1. Is there a way for app designer to detect the default drop down menu value at launch to hide something? Below is the code I wrote so far.

function DropDownValueChanged(app, event)

value = app.DropDown.Value;

if strcmp(value,'Option 1')

app.MassofobjectEditField.Visible= 'off';

else

app.MassofobjectEditField.Visible= 'on';

end

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Answer 1

Sven 2019-3-1

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https://ww2.mathworks.cn/matlabcentral/answers/447641-drop-down-menu-app-designer-values#answer_363312

编辑：Sven 2019-3-1

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The code won't execute because, it is a ValueChanged function which means it has to detect a change in its value to do something. This is not the case if you start it with Option 1 and want to do something when Option 1 is selected. You first have to change to another value and then back to Option 1.

If you want MassofobjectEditField to be hidden upon starting your app, you can call

app.DropDownValueChanged(app, [])

inside your startup function after the DropDown Menu is created. (See the comment below.) The startup function executes after starting your app and can be added by clicking the green plus and choosing the StartupFcn callback.

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Guillaume 2019-3-1

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I would not recommend doing this exactly, since you now have two different locations to edit if you ever change the logic of the code. Rather, I'd recommend firing off the event yourself at the end of the start up function. Then all the logic is contained in the callback.

So somewhere in the startup function, after the dropdown value has been set,

app.DropDownValueChanged(app, [])

to force the callback to execute.

Sven 2019-3-1