SnapHelper
abstract class SnapHelper : RecyclerView.OnFlingListener
kotlin.Any | ||
↳ | androidx.recyclerview.widget.RecyclerView.OnFlingListener | |
↳ | androidx.recyclerview.widget.SnapHelper |
Class intended to support snapping for a RecyclerView
.
SnapHelper tries to handle fling as well but for this to work properly, the RecyclerView.LayoutManager
must implement the RecyclerView.SmoothScroller.ScrollVectorProvider
interface or you should override onFling(int, int)
and handle fling manually.
Summary
Public constructors | |
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<init>() Class intended to support snapping for a |
Public methods | |
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open Unit |
attachToRecyclerView(@Nullable recyclerView: RecyclerView?) Attaches the |
abstract IntArray? |
calculateDistanceToFinalSnap(@NonNull layoutManager: RecyclerView.LayoutManager, @NonNull targetView: View) Override this method to snap to a particular point within the target view or the container view on any axis. |
open IntArray! |
calculateScrollDistance(velocityX: Int, velocityY: Int) Calculated the estimated scroll distance in each direction given velocities on both axes. |
abstract View? |
findSnapView(layoutManager: RecyclerView.LayoutManager!) Override this method to provide a particular target view for snapping. |
abstract Int |
findTargetSnapPosition(layoutManager: RecyclerView.LayoutManager!, velocityX: Int, velocityY: Int) Override to provide a particular adapter target position for snapping. |
open Boolean |
Protected methods | |
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open RecyclerView.SmoothScroller? |
createScroller(@NonNull layoutManager: RecyclerView.LayoutManager) Creates a scroller to be used in the snapping implementation. |
open LinearSmoothScroller? |
createSnapScroller(@NonNull layoutManager: RecyclerView.LayoutManager) Creates a scroller to be used in the snapping implementation. |
Public constructors
<init>
SnapHelper()
Class intended to support snapping for a RecyclerView
.
SnapHelper tries to handle fling as well but for this to work properly, the RecyclerView.LayoutManager
must implement the RecyclerView.SmoothScroller.ScrollVectorProvider
interface or you should override onFling(int, int)
and handle fling manually.
Public methods
attachToRecyclerView
open fun attachToRecyclerView(@Nullable recyclerView: RecyclerView?): Unit
Attaches the SnapHelper
to the provided RecyclerView, by calling RecyclerView#setOnFlingListener(RecyclerView.OnFlingListener)
. You can call this method with null
to detach it from the current RecyclerView.
Parameters | |
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recyclerView |
RecyclerView?: The RecyclerView instance to which you want to add this helper or null if you want to remove SnapHelper from the current RecyclerView. |
Exceptions | |
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IllegalArgumentException |
if there is already a RecyclerView.OnFlingListener attached to the provided RecyclerView . |
calculateDistanceToFinalSnap
@Nullable abstract fun calculateDistanceToFinalSnap(
@NonNull layoutManager: RecyclerView.LayoutManager,
@NonNull targetView: View
): IntArray?
Override this method to snap to a particular point within the target view or the container view on any axis.
This method is called when the SnapHelper
has intercepted a fling and it needs to know the exact distance required to scroll by in order to snap to the target view.
Parameters | |
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layoutManager |
RecyclerView.LayoutManager: the RecyclerView.LayoutManager associated with the attached RecyclerView |
targetView |
View: the target view that is chosen as the view to snap |
Return | |
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IntArray? |
the output coordinates the put the result into. out[0] is the distance on horizontal axis and out[1] is the distance on vertical axis. |
calculateScrollDistance
open fun calculateScrollDistance(
velocityX: Int,
velocityY: Int
): IntArray!
Calculated the estimated scroll distance in each direction given velocities on both axes.
Parameters | |
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velocityX |
Int: Fling velocity on the horizontal axis. |
velocityY |
Int: Fling velocity on the vertical axis. |
Return | |
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IntArray! |
array holding the calculated distances in x and y directions respectively. |
findSnapView
@Nullable abstract fun findSnapView(layoutManager: RecyclerView.LayoutManager!): View?
Override this method to provide a particular target view for snapping.
This method is called when the SnapHelper
is ready to start snapping and requires a target view to snap to. It will be explicitly called when the scroll state becomes idle after a scroll. It will also be called when the SnapHelper
is preparing to snap after a fling and requires a reference view from the current set of child views.
If this method returns null
, SnapHelper will not snap to any view.
Parameters | |
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layoutManager |
RecyclerView.LayoutManager!: the RecyclerView.LayoutManager associated with the attached RecyclerView |
Return | |
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View? |
the target view to which to snap on fling or end of scroll |
findTargetSnapPosition
abstract fun findTargetSnapPosition(
layoutManager: RecyclerView.LayoutManager!,
velocityX: Int,
velocityY: Int
): Int
Override to provide a particular adapter target position for snapping.
Parameters | |
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layoutManager |
RecyclerView.LayoutManager!: the RecyclerView.LayoutManager associated with the attached RecyclerView |
velocityX |
Int: fling velocity on the horizontal axis |
velocityY |
Int: fling velocity on the vertical axis |
Return | |
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Int |
the target adapter position to you want to snap or RecyclerView#NO_POSITION if no snapping should happen |
Protected methods
createScroller
@Nullable protected open fun createScroller(@NonNull layoutManager: RecyclerView.LayoutManager): RecyclerView.SmoothScroller?
Creates a scroller to be used in the snapping implementation.
Parameters | |
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layoutManager |
RecyclerView.LayoutManager: The RecyclerView.LayoutManager associated with the attached RecyclerView . |
Return | |
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RecyclerView.SmoothScroller? |
a RecyclerView.SmoothScroller which will handle the scrolling. |
createSnapScroller
@Nullable protected open funcreateSnapScroller(@NonNull layoutManager: RecyclerView.LayoutManager): LinearSmoothScroller?
Deprecated: use createScroller(RecyclerView.LayoutManager)
instead.
Creates a scroller to be used in the snapping implementation.
Parameters | |
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layoutManager |
RecyclerView.LayoutManager: The RecyclerView.LayoutManager associated with the attached RecyclerView . |
Return | |
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LinearSmoothScroller? |
a LinearSmoothScroller which will handle the scrolling. |