The reason for this behavior is that the values are set in the DropDownValueChanged instead of startupFcn.
If your intention is to initialize the values of the drop-down programmatically, you need to do that in ' startupFcn ' callback.
Alternatively, you can initialize the UI values directly from UI configuration parameters of the 'Design View'. However, I would personally recommend using the 'startupFcn' approach.
A quick tip: Why are you creating a new dropdown UI (check your 2 and 3 line numbers of your code) instead of updating the values?
Consider using the below approach.
function startupFcn(app)
value = app.DropDown.Value;
app.DropDown.Items = {'Red','Blue'};
end
Thanks, Prasanth
