Select/set ItemData index of drop down in App Designer

Hi folks,

I created an app in app designer which has an Edit Field where a user can enter an IP and a drop down menu where you can choose the last five entered IPs. By pressing a button 'OK' the value entered in the Edit Field is compared with a document in which i store the last five entered IPs if it already exists, the index get's changed an it is set to the first position of the document to keep it chronological. The value is also passed to the next GUI where some actions happen. I have also a button from the second GUI to get back to the first GUI (in case you want to change the IP).

My problem right now is that when I choose an IP out of the list let's say IP #3 the index is also set to 3. If I try to enter a new IP by pressing the button in GUI 2 I get an 'out of index' error while GUI 1 goes through my saved list but not starting with index 1 but with index 3. Is there a way to set the index on the first Item and not the last I choose?

app.previouslyusedPortsDropDown.ItemsData = [1,2,3,4,5];
load('ports.mat','ports')
for i=1:1:5
    app.previouslyusedPortsDropDown.Items(i) = cellstr(ports(i));
end

By leaving GUI 1 and entering GUI 2 I tried to clear all and delete GUI 1 to ensure everything get's loaded correctly as if I start the program out of nowhere.

[Mario Malic]

I do not completely understand the problem, but you can set the value by

app.previouslyusedPortsDropDown.Value = app.previouslyusedPortsDropDown.Items(1)

[Dominik Müller]

I found out that if I choose the first or the 5th element of the list and press okay (GUI 2 opens and GUI 1 closes) and get back to GUI 1 everything works fine. But if I choose ID 2-4 and get back to GUI 1 the out of index error occurs with the index of the chosen ID.

For example:

I choose ID 1 of the drop down and press okay --> GUI 2 opens. I want to connect to another device and press a button on GUI 2 --> GUI 1 opens perfectly. Now I choose the third ID listed in the drop down and press okay --> GUI 2 opens. I want to connect to another device and press a button on GUI 2 --> GUI 1 opens and the out of index error occurs: Index exceeds the number of array elements (3).

If I had chosen ID 4 of the list it would be (4) with the second ID it would be (2) in the error message. Only if I choose the first or last ID of the drop down list everything works fine.

[Mario Malic]

I think I'd need code snippet to see what's going on. It's weird that index error appears if you don't delete anything. Also, if you want to set some values when the program starts, you can use startupFcn callback.

Try running your app from command line and see what happens with the values in the workspace.

app=Nameoftheapp

[Dominik Müller]

I got the problem solved... it was my fault. In the function I shifted the chosen element to the first position of the array I deleted accidentally some of my items. This led to the error.

Now I followed this solution combined with a switch case and it seems to run correct:

https://www.mathworks.com/matlabcentral/answers/41528-move-element-in-array

[Mario Malic]

Great!

[Dominik Müller]

Nevertheless thanks for your support ;)