Thursday, February 18, 2016

Bootstrap modal dialog issue: Dropdown always closes

Last week, a developer reported a strange issue: he was using the Bootstrap modal dialog. On this dialog he added a dropdown control(a  KendoUI control in this case). The problem was that each time he opened up the dropdownlist to  select an item, it immediatelly closed again.

When we investigated the issue, we noticed that the moment the dropdown list opened, the Bootstrap modal dialog steals the focus and a blur event is triggered. This blur event makes the control close again.

After further investigation we discovered what was causing this behavior. The dropdownlist creates a hidden popup element on the page. This popup element is not part of the modal dialog content. This means that when you click on the popup element, the modal dialog thinks that you want to move out of the dialog and therefore triggers a blur event.

I noticed the same behavior not only with the KendoUI DropDownList control but also with other dropdown controls like  Select2.

We found 2 possible solutions that solve the issue(both of them work)

  • Solution 1 – Remove the tabindex=-1 from the modal dialog:

<div class="modal fade" tabindex="-1" role="dialog">
    
<div class="modal-dialog"> <!-content removed—></div>
</div>

  • Solution 2 – (In case of Kendo UI) Use the .appendTo method on the DropDownList control to add the popup to the content of the modal dialog:

.Popup(p => p.AppendTo("[selector]"))

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