DropdownButton in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a DropdownButton in Flutter?

A DropdownButton is a widget that shows a list of options when tapped, allowing the user to select one option from the list.

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How do you provide the list of options to a DropdownButton?

You provide a list of DropdownMenuItem widgets to the items property of the DropdownButton. Each item represents one selectable option.

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What property of DropdownButton holds the currently selected value?

The value property holds the currently selected item from the list of options.

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How do you update the selected value when the user picks a new option?

You use the onChanged callback, which receives the new selected value. Inside it, you update the state to reflect the new selection.

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Why should you use DropdownMenuItem widgets inside DropdownButton?

Because DropdownMenuItem defines each option's value and how it looks in the dropdown list, making the dropdown interactive and meaningful.

Which property of DropdownButton sets the list of selectable options?

A onChanged

B value

C selected

D items

The items property takes a list of DropdownMenuItem widgets that define the options.

What type of widget is used to represent each option inside a DropdownButton?

A DropdownMenuItem

B DropdownOption

C DropdownEntry

D DropdownChoice

Each option is a DropdownMenuItem widget.

How do you detect when the user selects a new option in a DropdownButton?

A Using the <code>onTap</code> callback

B Using the <code>onSelect</code> property

C Using the <code>onChanged</code> callback

D Using the <code>onPressed</code> property

The onChanged callback is called with the new value when the user selects an option.

What happens if the value property of DropdownButton is null?

A The dropdown crashes

B The dropdown shows no selected item

C The dropdown shows the first item selected

D The dropdown disables itself

If value is null, no item is selected initially.

Which of these is NOT a required property for a basic DropdownButton?

A icon

B value

C onChanged

D items

The icon property is optional and controls the dropdown arrow icon.

Explain how to create a simple dropdown menu in Flutter using DropdownButton.

Think about how you show options, track the selected one, and respond to user taps.

Describe the role of the onChanged callback in a DropdownButton.

It is how your app knows the user picked a different option.