Dismissible for swipe actions in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Dismissible widget in Flutter?

The Dismissible widget allows users to swipe a widget (usually a list item) to dismiss it, triggering an action like deleting or archiving.

beginner

Which property of Dismissible uniquely identifies the widget?

The key property is required and must be unique to identify the Dismissible widget in the widget tree.

beginner

How do you detect when a Dismissible widget has been swiped away?

Use the onDismissed callback, which is called when the widget is swiped and dismissed. It provides the swipe direction.

intermediate

What is the role of the background property in Dismissible?

The background property defines a widget shown behind the child when swiping, often used to show a delete icon or color to indicate the swipe action.

intermediate

Can you customize swipe directions in Dismissible? How?

Yes, by setting the direction property to values like DismissDirection.startToEnd or DismissDirection.horizontal to control allowed swipe directions.

What must you always provide to a Dismissible widget?

A A unique key

B An onTap callback

C A background color

D An icon

The key property uniquely identifies the Dismissible widget and is required.

Which callback is triggered when a Dismissible widget is swiped away?

A onDismissed

B onTap

C onSwipe

D onDragEnd

The onDismissed callback runs when the widget is dismissed by swiping.

What does the background property in Dismissible do?

A Handles the swipe animation

B Sets the widget's background color permanently

C Defines the swipe direction

D Shows a widget behind the child when swiping

The background widget appears behind the child during swipe to give visual feedback.

How can you restrict swipe to only left-to-right in Dismissible?

A Use <code>onSwipeLeft</code> callback

B Set <code>direction</code> to <code>DismissDirection.startToEnd</code>

C Set <code>direction</code> to <code>DismissDirection.endToStart</code>

D Use <code>swipeDirection</code> property

The direction property controls allowed swipe directions; startToEnd means left-to-right in LTR languages.

What happens if you do not provide a unique key to a Dismissible widget?

A The app crashes immediately

B The widget will be dismissed twice

C Flutter throws an error at runtime

D The widget cannot be swiped

Flutter requires a unique key for Dismissible widgets and throws a runtime error if missing.

Explain how to implement a swipe-to-delete list item using the Dismissible widget in Flutter.

Think about what each property does and how they work together to detect and respond to swipe.

Describe the user experience improvements that the background property adds to swipe actions.

Consider what the user sees behind the item as they swipe.