ViewDragHelper.Callback

fun clampViewPositionHorizontal(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.

fun clampViewPositionVertical(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.

fun getOrderedChildIndex(index: Int): Int

Called to determine the Z-order of child views.

fun getViewHorizontalDragRange(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.

fun getViewVerticalDragRange(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.

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.

fun onEdgeLock(edgeFlags: Int): Boolean

Called when the given edge may become locked. This can happen if an edge drag was preliminarily rejected before beginning, but after onEdgeTouched was called. This method should return true to lock this edge or false to leave it unlocked. The default behavior is to leave edges unlocked.

fun onEdgeTouched(edgeFlags: Int, pointerId: Int): Unit

Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured.

fun onViewCaptured(capturedChild: View, activePointerId: Int): Unit

Called when a child view is captured for dragging or settling. The ID of the pointer currently dragging the captured view is supplied. If activePointerId is identified as INVALID_POINTER the capture is programmatic instead of pointer-initiated.

fun onViewDragStateChanged(state: Int): Unit

Called when the drag state changes. See the STATE_* constants for more information.

fun onViewPositionChanged(
    changedView: View,
    left: Int,
    top: Int,
    dx: @Px Int,
    dy: @Px Int
): Unit

Called when the captured view's position changes as the result of a drag or settle.

fun onViewReleased(releasedChild: View, xvel: Float, yvel: Float): Unit

Called when the child view is no longer being actively dragged. The fling velocity is also supplied, if relevant. The velocity values may be clamped to system minimums or maximums.

Calling code may decide to fling or otherwise release the view to let it settle into place. It should do so using settleCapturedViewAt or flingCapturedView. If the Callback invokes one of these methods, the ViewDragHelper will enter STATE_SETTLING and the view capture will not fully end until it comes to a complete stop. If neither of these methods is invoked before onViewReleased returns, the view will stop in place and the ViewDragHelper will return to STATE_IDLE.

abstract fun tryCaptureView(child: View, pointerId: Int): Boolean

Called when the user's input indicates that they want to capture the given child view with the pointer indicated by pointerId. The callback should return true if the user is permitted to drag the given view with the indicated pointer.

ViewDragHelper may call this method multiple times for the same view even if the view is already captured; this indicates that a new pointer is trying to take control of the view.

If this method returns true, a call to onViewCaptured will follow if the capture is successful.