/**
* Computes the offsets based on the vertical and horizontal spacing values. The spacing
* computation has to ensure that the lane sizes are the same after applying the offsets. This
* means we have to shift the spacing unevenly across items depending on their position in the
* layout.
*/
public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
final BaseLayoutManager lm = (BaseLayoutManager) parent.getLayoutManager();
lm.getLaneForPosition(mTempLaneInfo, itemPosition, TwoWayLayoutManager.Direction.END);
final int lane = mTempLaneInfo.startLane;
final int laneSpan = lm.getLaneSpanForPosition(itemPosition);
final int laneCount = lm.getLanes().getCount();
final int itemCount = parent.getAdapter().getItemCount();
final boolean isVertical = lm.isVertical();
final boolean firstLane = (lane == 0);
final boolean secondLane = isSecondLane(lm, itemPosition, lane);
final boolean lastLane = (lane + laneSpan == laneCount);
final boolean beforeLastLane = (lane + laneSpan == laneCount - 1);
final int laneSpacing = (isVertical ? mHorizontalSpacing : mVerticalSpacing);
final int laneOffsetStart;
final int laneOffsetEnd;
if (firstLane) {
laneOffsetStart = 0;
} else if (lastLane && !secondLane) {
laneOffsetStart = (int) (laneSpacing * 0.75);
} else if (secondLane && !lastLane) {
laneOffsetStart = (int) (laneSpacing * 0.25);
} else {
laneOffsetStart = (int) (laneSpacing * 0.5);
}
if (lastLane) {
laneOffsetEnd = 0;
} else if (firstLane && !beforeLastLane) {
laneOffsetEnd = (int) (laneSpacing * 0.75);
} else if (beforeLastLane && !firstLane) {
laneOffsetEnd = (int) (laneSpacing * 0.25);
} else {
laneOffsetEnd = (int) (laneSpacing * 0.5);
}
final boolean isFirstInLane = isFirstChildInLane(lm, itemPosition);
final boolean isLastInLane =
!mAddSpacingAtEnd && isLastChildInLane(lm, itemPosition, itemCount);
if (isVertical) {
outRect.left = laneOffsetStart;
outRect.top = (isFirstInLane ? 0 : mVerticalSpacing / 2);
outRect.right = laneOffsetEnd;
outRect.bottom = (isLastInLane ? 0 : mVerticalSpacing / 2);
} else {
outRect.left = (isFirstInLane ? 0 : mHorizontalSpacing / 2);
outRect.top = laneOffsetStart;
outRect.right = (isLastInLane ? 0 : mHorizontalSpacing / 2);
outRect.bottom = laneOffsetEnd;
}
}
