How to solve ‘There should be exactly one item with DropdownButton ’
In Flutter, a dropdown button is a UI widget that provides a list of options for users to choose from in a dropdown menu. It consists of a button that displays the currently selected option and an arrow icon that, when tapped, expands a menu with available options.
When the user selects an option from the dropdown menu, the button updates its display to show the selected value. Flutter provides the DropdownButton widget to implement this functionality.
While implementing this functionality developers can face some problems. We are going to discuss a problem from one of them. The issue is ‘There should be exactly one item with DropdownButton’. This could be confusing for developers. It shows red screen on device when we encountered this problem.
Let’s discuss why this issue comes and how to solve this one.
Reasons and solutions of ‘There should be exactly one item with DropdownButton‘
As we know that DropdownButton requires a property of items.
1- Items in DropdownButton
This items property is a list of DropdownMenuItem. We have to provide a list of DropdownMenuItem to DropdownButton. User has to select a single item from this list of items. Every single DropdownMenuItem requires two properties. First one is child and second one is value. The value property of the DropdownMenuItem can be of any data type, such as strings, numbers, or custom objects. This value should be unique in the list of DropdownMenuItem. If this value is duplicated in items list, then we will face this problem for dropdownbutton in flutter. So make sure that there is exactly one item with a single value. No one value is duplicated.
2- Value in DropdownButton
The value property of DropdownButton represents the currently selected option. We have to make sure that this value also exists in the list of DropdownMenuItem. If this value not exists in that list, then also the same error we will face. So make sure that this value exists in items list.
Conclusion
In this article we discussed the reasons and solutions of a common error that developers face while working with DropdownButtin in flutter. Hope this will help you to overcome these type of errors in your future projects.
