Programming Android with Kotlin by Pierre-Olivier Laurence & Amanda Hinchman-Dominguez & Mike Dunn

Author:Pierre-Olivier Laurence & Amanda Hinchman-Dominguez & Mike Dunn [Pierre-Olivier Laurence]
Language: eng
Format: epub
Publisher: O'Reilly Media, Inc.
Published: 2021-08-24T16:00:00+00:00

Cancellation

Handling task cancellation is a critical part of an Android application. When a user navigates for the first time to the view displaying the list of hikes along with statistics and weather, a decent amount of coroutines are started from the ViewModel. If for some reason the user decides to leave the view, then the tasks launched by the view-model are probably running for nothing. Unless of course the user later navigates back to the view - but it’s dangerous to assume that. To avoid wasting resources, a good practice in this scenario is to cancel all ongoing tasks related to views no longer needed. This is a good example of cancellation you might implement yourself, as part of your application design. There’s another kind of cancellation: the one that happens when something bad happens. So we’ll distinguish two types of cancellation:

Designed cancellation - For example, you could decide to cancel a task after a user tapped a “Cancel” button in a custom or arbitrary UI.

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