interface NestedScrollingChild3 : NestedScrollingChild2
This interface should be implemented by
View subclasses that wish to support dispatching nested scrolling operations to a cooperating parent
Classes implementing this interface should create a final instance of a
NestedScrollingChildHelper as a field and delegate any View methods to the
NestedScrollingChildHelper methods of the same signature.
Views invoking nested scrolling functionality should always do so from the relevant
ViewParentCompat compatibility shim static methods. This ensures interoperability with nested scrolling views on all versions of Android.
dispatchNestedFling(velocityX: Float, velocityY: Float, consumed: Boolean)
Dispatch a fling to a nested scrolling parent.
This method should be used to indicate that a nested scrolling child has detected suitable conditions for a fling. Generally this means that a touch scroll has ended with a
velocity in the direction of scrolling that meets or exceeds the
minimum fling velocity along a scrollable axis.
If a nested scrolling child view would normally fling but it is at the edge of its own content, it can use this method to delegate the fling to its nested scrolling parent instead. The parent may optionally consume the fling or observe a child fling.
dispatchNestedPreFling(velocityX: Float, velocityY: Float)
Dispatch a fling to a nested scrolling parent before it is processed by this view.
Nested pre-fling events are to nested fling events what touch intercept is to touch and what nested pre-scroll is to nested scroll.
dispatchNestedPreFling offsets an opportunity for the parent view in a nested fling to fully consume the fling before the child view consumes it. If this method returns
true, a nested parent view consumed the fling and this view should not scroll as a result.
For a better user experience, only one view in a nested scrolling chain should consume the fling at a time. If a parent view consumed the fling this method will return false. Custom view implementations should account for this in two ways:
- If a custom view is paged and needs to settle to a fixed page-point, do not call
dispatchNestedPreFling; consume the fling and settle to a valid position regardless.
- If a nested parent does consume the fling, this view should not scroll at all, even to settle back to a valid idle position.
Views should also not offer fling velocities to nested parent views along an axis where scrolling is not currently supported; a
ScrollView should not offer a horizontal fling velocity to its parents since scrolling along that axis is not permitted and carrying velocity along that motion does not make sense.
dispatchNestedPreScroll(dx: Int, dy: Int, @Nullable consumed: IntArray?, @Nullable offsetInWindow: IntArray?)
Dispatch one step of a nested scroll in progress before this view consumes any portion of it.
Nested pre-scroll events are to nested scroll events what touch intercept is to touch.
dispatchNestedPreScroll offers an opportunity for the parent view in a nested scrolling operation to consume some or all of the scroll operation before the child view consumes it.
dispatchNestedScroll(dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int, @Nullable offsetInWindow: IntArray?)
Dispatch one step of a nested scroll in progress.
Implementations of views that support nested scrolling should call this to report info about a scroll in progress to the current nested scrolling parent. If a nested scroll is not currently in progress or nested scrolling is not
enabled for this view this method does nothing.
Compatible View implementations should also call