Debounce Mutation State Policy
Author: Pablisco
This is an alternate method of debouncing state changes in Jetpack Compose.
Using this technique, you can leverage a custom SnapshotMutationPolicy to accomplish the same debouncing behavior. The main difference is that this approach uses the default mutableStateOf implementation with a custom mutation policy instead.
| /** | |
| * Returns a [SnapshotMutationPolicy] implementation that applies a debounce mechanism to mutation events. | |
| * | |
| * @param debounceTime The time window in milliseconds within which mutation events are considered to be the same. | |
| * @return An instance of [SnapshotMutationPolicy] that applies a debounce mechanism. | |
| * | |
| * @param T The type of the snapshot. | |
| */ | |
| fun <T> debounceMutationPolicy( | |
| debounceTime: Long = 500, | |
| ): SnapshotMutationPolicy<T> = object : SnapshotMutationPolicy<T> { | |
| var lastUpdate = 0L | |
| override fun equivalent(a: T, b: T): Boolean = checkEquivalence(a, b).also { updateIfNeeded() } | |
| private fun updateIfNeeded() = apply { if (isUpdateTime()) lastUpdate = now() } | |
| private fun checkEquivalence(a: T, b: T): Boolean = if (isUpdateTime()) a == b else CancelMutation | |
| private fun isUpdateTime() = now() - lastUpdate > debounceTime | |
| } | |
| /** | |
| * Determines whether a mutation should be canceled or not. | |
| * | |
| * The value of this property determines whether a mutation should be canceled or not based on the conditions defined | |
| * in the "checkEquivalence" function. | |
| * If CancelMutation is set to `true`, the "checkEquivalence" function will return `true` if the time between the last | |
| * update and the current time is greater than the debounce time. | |
| * | |
| * Otherwise, it will return the result of the equality comparison between the two provided values. | |
| */ | |
| private const val CancelMutation = true |
| mutableStateOf(initialValue, debounceMutationPolicy()) |
It’s a great reminder that in coding, flexibility is key. Whether you choose to extend MutableState or use a custom mutation policy, you’ve got options to tailor your state management to your needs.
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