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How to find the item order number in List Box in App designer?

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Faez Alkadi 2019-9-17

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评论： Seonggon Kim 2023-2-18

I have a List box named "Numbers" that has the same 4 items, they all are the number 5. How can I pick the Item3 (The third in order) to change it to 3.

I used [~,idx] = ismember(app.NumbersListBox.Value,app.NumbersListBox.Items);

But I alwyas get to change the first on because the Value are the same.

How can I find inx using "Item number" instead of "Value" ?

Thank you so much

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Adam 2019-9-17

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Surely if you already know the index then just use it where you would use the 'idx' that you extract above (which is always 1). You should just be able to index into the list of items with this.

Faez Alkadi 2019-9-17

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I'm sorry, But I don't understand.

Adam 2019-9-17

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You said you want item 3. That is the 3rd element of the listbox. What were you going to do with 'idx' from your above code? Just use 3 instead of idx as it will be the 3rd item. I haven't really used list boxes in App designer, but at a guess

app.NumbersListBox.items{3}

will return this.

Ankit 2019-9-17

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Hallo Faez,

When your listbox have same values for e.g.

app.NumberListBox.Items = {'5', '5', '5', '5'};

[~,idx] = ismember(app.NumbersListBox.Value,app.NumbersListBox.Items);

The value of idx is always 1.

In case your list box have diff values for e.g. app.NumberListBox.Items = {'1', '2', '3', '4'};

[~,idx] = ismember(app.NumbersListBox.Value,app.NumbersListBox.Items);

The value of idx is selected item.

You have specific use case where all the values are same?

Faez Alkadi 2019-9-17

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编辑：Faez Alkadi 2019-9-17

Adam,

this app.NumbersListBox.items{3} thing will work manual by changing the item nuber manually every time. I need it to be general case.

Hi Falcon;

Yes, I have specific use case where all the values are same.

Thats why when I choose an Item to change I alway change the first Item. I need to find a way to change an Item based on its order in the group not its Value.

Thank you

Adam 2019-9-17

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How can you have a general case if all the list items are the same? You have to pick up the index from somewhere, whether you hard-code it as 3 or get it from somewhere else, but the idea is still the same.

Ned 2019-9-18

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How does your app determine which of the numbers to change? user input? Because like Adam said, if you're programming it, you can just select Item 3. otherwise, I'm thinking you could use something along the lines of

find(ismember(app.NumbersListBox.Items,app.NumbersListBox.Value));

to get the index of all the items indicated by ListBox.Value

Faez Alkadi 2019-9-18

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Hi Ned.

I program it on the app interface. And when I pick a part from the list using the curser it just read the Value of the item I picked and find the index of it. I need it to read the place of the item in the list. instead of the Value.

Thank you

Ned 2019-9-18