public LinearLayoutManager(int orientation)
{
mOrientation = orientation;
mOrientationHelper = OrientationHelper.CreateOrientationHelper(this, mOrientation);
mLayoutState = new LayoutState();
mLayoutState.Offset = mOrientationHelper.GetStartAfterPadding();
}
public void ResetLayout(int direction, bool canUseExistingSpace, float space, OrientationHelper orientationHelper, LinearLayoutManager linearLayoutManager)
{
this.Extra = 0;
this.LayoutDirection = direction;
float scrollingOffset = 0.0f;
if (direction == LayoutState.LAYOUT_END)
{
this.Extra += orientationHelper.GetEndPadding();
FlexibleViewViewHolder endChild = linearLayoutManager.GetChildClosestToEnd();
if (endChild != null)
{
// the direction in which we are traversing children
this.ItemDirection = linearLayoutManager.mShouldReverseLayout ? LayoutState.ITEM_DIRECTION_HEAD
: LayoutState.ITEM_DIRECTION_TAIL;
this.CurrentPosition = endChild.LayoutPosition + linearLayoutManager.mLayoutState.ItemDirection;
this.Offset = orientationHelper.GetViewHolderEnd(endChild);
scrollingOffset = orientationHelper.GetViewHolderEnd(endChild) - orientationHelper.GetEndAfterPadding();
}
}
else
{
this.Extra += orientationHelper.GetStartAfterPadding();
FlexibleViewViewHolder startChild = linearLayoutManager.GetChildClosestToStart();
if (startChild != null)
{
this.ItemDirection = linearLayoutManager.mShouldReverseLayout ? LayoutState.ITEM_DIRECTION_TAIL
: LayoutState.ITEM_DIRECTION_HEAD;
this.CurrentPosition = startChild.LayoutPosition + linearLayoutManager.mLayoutState.ItemDirection;
this.Offset = orientationHelper.GetViewHolderStart(startChild);
scrollingOffset = -orientationHelper.GetViewHolderStart(startChild) + orientationHelper.GetStartAfterPadding();
}
}
this.Available = space;
if (canUseExistingSpace)
{
this.Available -= scrollingOffset;
}
this.ScrollingOffset = scrollingOffset;
}
public override float ComputeScrollOffset()
{
FlexibleViewViewHolder startChild = FindFirstVisibleItemView();
FlexibleViewViewHolder endChild = FindLastVisibleItemView();
if (ChildCount == 0 || startChild == null || endChild == null)
{
return(0);
}
int minPosition = Math.Min(startChild.LayoutPosition, endChild.LayoutPosition);
int maxPosition = Math.Max(startChild.LayoutPosition, endChild.LayoutPosition);
int itemsBefore = mShouldReverseLayout
? Math.Max(0, ItemCount - maxPosition - 1)
: Math.Max(0, minPosition);
float laidOutArea = Math.Abs(mOrientationHelper.GetViewHolderEnd(endChild)
- mOrientationHelper.GetViewHolderStart(startChild));
int itemRange = Math.Abs(startChild.LayoutPosition - endChild.LayoutPosition) + 1;
float avgSizePerRow = laidOutArea / itemRange;
return((float)Math.Round(itemsBefore * avgSizePerRow + (mOrientationHelper.GetStartAfterPadding()
- mOrientationHelper.GetViewHolderStart(startChild))));
}
