Callback

Kotlin |Java

abstract class Callback

kotlin.Any
↳	androidx.customview.widget.ViewDragHelper.Callback

A Callback is used as a communication channel with the ViewDragHelper back to the parent view using it. on*methods are invoked on siginficant events and several accessor methods are expected to provide the ViewDragHelper with more information about the state of the parent view upon request. The callback also makes decisions governing the range and draggability of child views.

Summary

Public constructors
`<init>()` A Callback is used as a communication channel with the ViewDragHelper back to the parent view using it.

Public methods
open Int	`clampViewPositionHorizontal(@NonNull child: View, left: Int, dx: Int)` Restrict the motion of the dragged child view along the horizontal axis.
open Int	`clampViewPositionVertical(@NonNull child: View, top: Int, dy: Int)` Restrict the motion of the dragged child view along the vertical axis.
open Int	`getOrderedChildIndex(index: Int)` Called to determine the Z-order of child views.
open Int	`getViewHorizontalDragRange(@NonNull child: View)` Return the magnitude of a draggable child view's horizontal range of motion in pixels.
open Int	`getViewVerticalDragRange(@NonNull child: View)` Return the magnitude of a draggable child view's vertical range of motion in pixels.
open Unit	`onEdgeDragStarted(edgeFlags: Int, pointerId: Int)` Called when the user has started a deliberate drag away from one of the subscribed edges in the parent view while no child view is currently captured.
open Boolean	`onEdgeLock(edgeFlags: Int)` Called when the given edge may become locked.
open Unit	`onEdgeTouched(edgeFlags: Int, pointerId: Int)` Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured.
open Unit	`onViewCaptured(@NonNull capturedChild: View, activePointerId: Int)` Called when a child view is captured for dragging or settling.
open Unit	`onViewDragStateChanged(state: Int)` Called when the drag state changes.
open Unit	`onViewPositionChanged(@NonNull changedView: View, left: Int, top: Int, @Px dx: Int, @Px dy: Int)` Called when the captured view's position changes as the result of a drag or settle.
open Unit	`onViewReleased(@NonNull releasedChild: View, xvel: Float, yvel: Float)` Called when the child view is no longer being actively dragged.
abstract Boolean	`tryCaptureView(@NonNull child: View, pointerId: Int)` Called when the user's input indicates that they want to capture the given child view with the pointer indicated by pointerId.

Public constructors

<init>

Callback()

Public methods

clampViewPositionHorizontal

open fun clampViewPositionHorizontal(
    @NonNull child: View, 
    left: Int, 
    dx: Int
): Int

Restrict the motion of the dragged child view along the horizontal axis. The default implementation does not allow horizontal motion; the extending class must override this method and provide the desired clamping.

Parameters
`child`	View: Child view being dragged
`left`	Int: Attempted motion along the X axis
`dx`	Int: Proposed change in position for left

Return
`Int`	The new clamped position for left

clampViewPositionVertical

open fun clampViewPositionVertical(
    @NonNull child: View, 
    top: Int, 
    dy: Int
): Int

Restrict the motion of the dragged child view along the vertical axis. The default implementation does not allow vertical motion; the extending class must override this method and provide the desired clamping.

Parameters
`child`	View: Child view being dragged
`top`	Int: Attempted motion along the Y axis
`dy`	Int: Proposed change in position for top

Return
`Int`	The new clamped position for top

getOrderedChildIndex

open fun getOrderedChildIndex(index: Int): Int

Called to determine the Z-order of child views.

Parameters
`index`	Int: the ordered position to query for

Return
`Int`	index of the view that should be ordered at position `index`

getViewHorizontalDragRange

open fun getViewHorizontalDragRange(@NonNull child: View): Int

Return the magnitude of a draggable child view's horizontal range of motion in pixels. This method should return 0 for views that cannot move horizontally.

Parameters
`child`	View: Child view to check

Return
`Int`	range of horizontal motion in pixels

getViewVerticalDragRange

open fun getViewVerticalDragRange(@NonNull child: View): Int

Return the magnitude of a draggable child view's vertical range of motion in pixels. This method should return 0 for views that cannot move vertically.

Parameters
`child`	View: Child view to check

Return
`Int`	range of vertical motion in pixels

onEdgeDragStarted

open fun onEdgeDragStarted(
    edgeFlags: Int, 
    pointerId: Int
): Unit

Called when the user has started a deliberate drag away from one of the subscribed edges in the parent view while no child view is currently captured.

Parameters
`edgeFlags`	Int: A combination of edge flags describing the edge(s) dragged
`pointerId`	Int: ID of the pointer touching the described edge(s)

See Also