NestedScrollDispatcher

class NestedScrollDispatcher

Nested scroll events dispatcher to notify the nested scroll system about the scrolling events that are happening on the element.

If the element/modifier itself is able to receive scroll events (from the touch, fling, mouse, etc) and it would like to respect nested scrolling by notifying elements above, it should properly dispatch nested scroll events when being scrolled

It is important to dispatch these events at the right time, provide valid information to the parents and react to the feedback received from them in order to provide good user experience with other nested scrolling nodes.

Properties

val coroutineScope: CoroutineScope

Get the outer coroutine scope to dispatch nested fling on.

There might be situations when then component that is dispatching preFling or postFling to parent can be disposed together with its scope, so it's recommended to use launch nested fling dispatch using this scope to prevent abrupt scrolling user experience.

Note: this scope is retrieved from the parent nestedScroll participants, unless the node knows its parent (which is usually after first composition commits), this will throw IllegalStateException.

Functions

fun dispatchPreScroll(available: Offset, source: NestedScrollSource): Offset

Dispatch pre scroll pass. This triggers NestedScrollConnection.onPreScroll on all the ancestors giving them possibility to pre-consume delta if they desire so.

Parameters

Returns

fun dispatchPostScroll(
        consumed: Offset,
        available: Offset,
        source: NestedScrollSource,
    ): Offset

Dispatch nested post-scrolling pass. This triggers NestedScrollConnection.onPostScroll on all the ancestors giving them possibility to react of the scroll deltas that are left after the dispatching node itself and other NestedScrollConnections below consumed the desired amount.

Parameters

Returns

suspend fun dispatchPreFling(available: Velocity): Velocity

Dispatch pre fling pass and suspend until all the interested participants performed velocity pre consumption. This triggers NestedScrollConnection.onPreFling on all the ancestors giving them a possibility to react on the fling that is about to happen and consume part of the velocity.

Parameters

Returns

suspend fun dispatchPostFling(consumed: Velocity, available: Velocity): Velocity

Dispatch post fling pass and suspend until all the interested participants performed velocity process. This triggers NestedScrollConnection.onPostFling on all the ancestors, giving them possibility to react of the velocity that is left after the dispatching node itself flung with the desired amount.

Parameters

Returns