public override int FindTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocityX, int velocityY)
{
if (CurrentTargetPosition == -1)
{
CurrentTargetPosition = base.FindTargetSnapPosition(layoutManager, velocityX, velocityY);
return(CurrentTargetPosition);
}
var increment = 1;
if (layoutManager.CanScrollHorizontally())
{
if (velocityX < 0)
{
increment = -1;
}
}
else if (layoutManager.CanScrollVertically())
{
if (velocityY < 0)
{
increment = -1;
}
}
if (IsLayoutReversed(layoutManager))
{
increment = increment * -1;
}
CurrentTargetPosition = CurrentTargetPosition + increment;
return(CurrentTargetPosition);
}
public override int[] CalculateDistanceToFinalSnap(RecyclerView.LayoutManager layoutManager, AView targetView)
{
var orientationHelper = CreateOrientationHelper(layoutManager);
var isHorizontal = layoutManager.CanScrollHorizontally();
var rtl = isHorizontal && IsLayoutReversed(layoutManager);
var distance = rtl
? -orientationHelper.GetDecoratedStart(targetView)
: orientationHelper.TotalSpace - orientationHelper.GetDecoratedEnd(targetView);
return(isHorizontal
? new[] { -distance, 1 }
: new[] { 1, -distance });
}
protected bool IsAtLeastHalfVisible(AView view, RecyclerView.LayoutManager layoutManager)
{
var orientationHelper = CreateOrientationHelper(layoutManager);
var reversed = IsLayoutReversed(layoutManager);
var isHorizontal = layoutManager.CanScrollHorizontally();
// Find the size of the view (including margins, etc.)
var size = orientationHelper.GetDecoratedMeasurement(view);
var portionInViewPort = VisiblePortion(view, orientationHelper, reversed && isHorizontal);
// Is the first visible view at least halfway on screen?
return(portionInViewPort >= size / 2);
}
public override int[] CalculateDistanceToFinalSnap(RecyclerView.LayoutManager layoutManager, View targetView)
{
int[] result = new int[2];
result[0] = layoutManager.CanScrollHorizontally()
? DistanceToStart(targetView, GetHorizontalHelper(layoutManager))
: 0;
result[1] = layoutManager.CanScrollVertically()
? DistanceToStart(targetView, GetVerticalHelper(layoutManager))
: 0;
return(result);
}
public override int FindTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocityX, int velocityY)
{
var itemCount = layoutManager.ItemCount;
//reset CurrentTargetPosition if ItemCount Changed is requested
//We could be adding a item before the CurrentTargetPosition
if (_previousCount != itemCount)
{
CurrentTargetPosition = -1;
_previousCount = itemCount;
}
if (CurrentTargetPosition == -1)
{
CurrentTargetPosition = base.FindTargetSnapPosition(layoutManager, velocityX, velocityY);
return(CurrentTargetPosition);
}
var increment = 1;
if (layoutManager.CanScrollHorizontally())
{
if (velocityX < 0)
{
increment = -1;
}
}
else if (layoutManager.CanScrollVertically())
{
if (velocityY < 0)
{
increment = -1;
}
}
if (IsLayoutReversed(layoutManager))
{
increment *= -1;
}
if (CurrentTargetPosition == itemCount - 1 && increment == 1)
{
return(CurrentTargetPosition);
}
CurrentTargetPosition = CurrentTargetPosition + increment;
return(CurrentTargetPosition);
}
public override View FindSnapView(RecyclerView.LayoutManager layoutManager)
{
if (!(layoutManager is LinearLayoutManager))
{
return(base.FindSnapView(layoutManager));
}
OrientationHelper helper = layoutManager.CanScrollHorizontally()
? GetHorizontalHelper(layoutManager)
: GetVerticalHelper(layoutManager);
var startView = GetStartView(layoutManager, helper, out int viewPosition);
// System.Diagnostics.Debug.WriteLine($"DEBUG_SCROLL: FindSnapView ( viewPosition: {viewPosition} )");
return(startView);
}
protected int[] CalculateDistanceToFinalSnap(RecyclerView.LayoutManager layoutManager, AView targetView,
int direction = 1)
{
var orientationHelper = CreateOrientationHelper(layoutManager);
var isHorizontal = layoutManager.CanScrollHorizontally();
var rtl = isHorizontal && IsLayoutReversed(layoutManager);
var size = orientationHelper.GetDecoratedMeasurement(targetView);
var hiddenPortion = size - VisiblePortion(targetView, orientationHelper, rtl);
var distance = (rtl ? hiddenPortion : -hiddenPortion) * direction;
return(isHorizontal
? new[] { distance, 1 }
: new[] { 1, distance });
}
public override View FindSnapView(RecyclerView.LayoutManager layoutManager)
{
if (!(layoutManager is LinearLayoutManager))
{
return(base.FindSnapView(layoutManager));
}
OrientationHelper helper = layoutManager.CanScrollHorizontally()
? GetHorizontalHelper(layoutManager)
: GetVerticalHelper(layoutManager);
var startView = GetStartView(layoutManager, helper, out int viewPosition);
InternalLogger.Info($"FindSnapView ( viewPosition: {viewPosition} )");
ReleaseIsBusy(startView);
return(startView);
}
protected static OrientationHelper CreateOrientationHelper(RecyclerView.LayoutManager layoutManager)
{
return(layoutManager.CanScrollHorizontally()
? OrientationHelper.CreateHorizontalHelper(layoutManager)
: OrientationHelper.CreateVerticalHelper(layoutManager));
}