public override int FillToEnd(int leadingEdge, int markerLine, int anchorPosition, SectionData sd, LayoutState state)
{
int itemCount = state.recyclerState.ItemCount;
for (int i = anchorPosition; i < itemCount; i++)
{
if (markerLine >= leadingEdge)
{
break;
}
LayoutState.View next = state.GetView(i);
LayoutManager.LayoutParams lp = next.LayoutParams;
if (lp.FirstPosition != sd.firstPosition)
{
state.CacheView(i, next.view);
break;
}
measureChild(next, sd);
markerLine = layoutChild(next, markerLine, LayoutManager.Direction.END, sd, state);
AddView(next, i, LayoutManager.Direction.END, state);
}
return(markerLine);
}
private int layoutChild(LayoutState.View child, int markerLine, LayoutManager.Direction direction, SectionData sd, LayoutState state)
{
int height = mLayoutManager.GetDecoratedMeasuredHeight(child.view);
int width = mLayoutManager.GetDecoratedMeasuredWidth(child.view);
int left = state.isLTR ? sd.contentStart : sd.contentEnd;
int right = left + width;
int top;
int bottom;
if (direction == LayoutManager.Direction.END)
{
top = markerLine;
bottom = top + height;
}
else
{
bottom = markerLine;
top = bottom - height;
}
mLayoutManager.LayoutDecorated(child.view, left, top, right, bottom);
if (direction == LayoutManager.Direction.END)
{
markerLine = mLayoutManager.GetDecoratedBottom(child.view);
}
else
{
markerLine = mLayoutManager.GetDecoratedTop(child.view);
}
return(markerLine);
}
public override int ComputeHeaderOffset(int firstVisiblePosition, SectionData sd, LayoutState state)
{
/*
* Work from an assumed overlap and add heights from the start until the overlap is zero or
* less, or the current position (or max items) is reached.
*/
int areaAbove = 0;
for (int position = sd.firstPosition + 1; areaAbove < sd.headerHeight && position < firstVisiblePosition; position++)
{
// Look to see if the header overlaps with the displayed area of the mSection.
LayoutState.View child = state.GetView(position);
measureChild(child, sd);
areaAbove += mLayoutManager.GetDecoratedMeasuredHeight(child.view);
state.CacheView(position, child.view);
}
if (areaAbove == sd.headerHeight)
{
return(0);
}
else if (areaAbove > sd.headerHeight)
{
return(1);
}
else
{
return(-areaAbove);
}
}
/// <summary>
/// Fill a row.
/// </summary>
/// <param name="markerLine"> Line indicating the top edge of the row. </param>
/// <param name="anchorPosition"> Position of the first view in the row. </param>
/// <param name="direction"> Direction of edge to fill towards. </param>
/// <param name="measureRowItems"> Measure the row items. </param>
/// <param name="sd"> Section data. </param>
/// <param name="state"> Layout state. </param>
/// <returns> The height of the new row. </returns>
public int fillRow(int markerLine, int anchorPosition, LayoutManager.Direction direction, bool measureRowItems, SectionData sd, LayoutState state)
{
int rowHeight = 0;
LayoutState.View[] views = new LayoutState.View[mNumColumns];
for (int i = 0; i < mNumColumns; i++)
{
int position = anchorPosition + i;
if (position >= state.recyclerState.ItemCount)
{
break;
}
LayoutState.View view = state.GetView(position);
if (view.LayoutParams.FirstPosition != sd.firstPosition)
{
state.CacheView(position, view.view);
break;
}
if (measureRowItems)
{
MeasureChild(view, sd);
}
else
{
state.DecacheView(i + anchorPosition);
}
rowHeight = Math.Max(rowHeight, mLayoutManager.GetDecoratedMeasuredHeight(view.view));
views[i] = view;
}
bool directionIsStart = direction == LayoutManager.Direction.START;
if (directionIsStart)
{
markerLine -= rowHeight;
}
for (int i = 0; i < mNumColumns; i++)
{
int col = directionIsStart ? mNumColumns - i - 1 : i;
if (views[col] == null)
{
continue;
}
LayoutChild(views[col], markerLine, col, rowHeight, sd, state);
AddView(views[col], col + anchorPosition, direction, state);
}
return(rowHeight);
}
protected int AddView(LayoutState.View child, int position, LayoutManager.Direction direction, LayoutState state)
{
int addIndex;
if (direction == LayoutManager.Direction.START)
{
addIndex = 0;
}
else
{
addIndex = mLayoutManager.ChildCount;
}
state.DecacheView(position);
mLayoutManager.AddView(child.view, addIndex);
return(addIndex);
}
/// <summary>
/// Layout out a view for the given column in a row. Views that have a height param of
/// MATCH_PARENT are fixed to the height of the row.
/// </summary>
/// <param name="child"> View to lay out. </param>
/// <param name="top"> Line indicating the top edge of the row. </param>
/// <param name="col"> Column view is being placed into. </param>
/// <param name="rowHeight"> Height of the row. </param>
/// <param name="sd"> Section data. </param>
/// <param name="state"> Layout state. </param>
private void LayoutChild(LayoutState.View child, int top, int col, int rowHeight, SectionData sd, LayoutState state)
{
int height;
if (child.LayoutParams.Height == LayoutManager.LayoutParams.MatchParent)
{
height = rowHeight;
}
else
{
height = mLayoutManager.GetDecoratedMeasuredHeight(child.view);
}
int width = mLayoutManager.GetDecoratedMeasuredWidth(child.view);
col = AdjustColumnForLayoutDirection(col, state.isLTR);
int bottom = top + height;
int left = (state.isLTR ? sd.contentStart : sd.contentEnd) + col * mColumnWidth;
int right = left + width;
mLayoutManager.LayoutDecorated(child.view, left, top, right, bottom);
}
public override int FillToStart(int leadingEdge, int markerLine, int anchorPosition, SectionData sd, LayoutState state)
{
// Check to see if we have to adjust for minimum section height. We don't if there is an
// attached non-header view in this section.
bool applyMinHeight = false;
for (int i = 0; i < state.recyclerState.ItemCount; i++)
{
View check = mLayoutManager.GetChildAt(0);
if (check == null)
{
applyMinHeight = false;
break;
}
LayoutManager.LayoutParams checkParams = (LayoutManager.LayoutParams)check.LayoutParameters;
if (checkParams.FirstPosition != sd.firstPosition)
{
applyMinHeight = true;
break;
}
if (!checkParams.isHeader)
{
applyMinHeight = false;
break;
}
}
// Work out offset to marker line by measuring items from the end. If section height is less
// than min height, then adjust marker line and then lay out items.
int measuredPositionsMarker = -1;
int sectionHeight = 0;
int minHeightOffset = 0;
if (applyMinHeight)
{
for (int i = anchorPosition; i >= 0; i--)
{
LayoutState.View measure = state.GetView(i);
state.CacheView(i, measure.view);
LayoutManager.LayoutParams lp = measure.LayoutParams;
if (lp.FirstPosition != sd.firstPosition)
{
break;
}
if (lp.isHeader)
{
continue;
}
measureChild(measure, sd);
sectionHeight += mLayoutManager.GetDecoratedMeasuredHeight(measure.view);
measuredPositionsMarker = i;
if (sectionHeight >= sd.minimumHeight)
{
break;
}
}
if (sectionHeight < sd.minimumHeight)
{
minHeightOffset = sectionHeight - sd.minimumHeight;
markerLine += minHeightOffset;
}
}
for (int i = anchorPosition; i >= 0; i--)
{
if (markerLine - minHeightOffset < leadingEdge)
{
break;
}
LayoutState.View next = state.GetView(i);
LayoutManager.LayoutParams lp = next.LayoutParams;
if (lp.isHeader)
{
state.CacheView(i, next.view);
break;
}
if (lp.FirstPosition != sd.firstPosition)
{
state.CacheView(i, next.view);
break;
}
if (!applyMinHeight || i < measuredPositionsMarker)
{
measureChild(next, sd);
}
else
{
state.DecacheView(i);
}
markerLine = layoutChild(next, markerLine, LayoutManager.Direction.START, sd, state);
AddView(next, i, LayoutManager.Direction.START, state);
}
return(markerLine);
}
private void measureChild(LayoutState.View child, SectionData sd)
{
mLayoutManager.MeasureChildWithMargins(child.view, sd.TotalMarginWidth, 0);
}
public override int FillToEnd(int leadingEdge, int markerLine, int anchorPosition, SectionData sd, LayoutState state)
{
if (markerLine >= leadingEdge)
{
return(markerLine);
}
int itemCount = state.recyclerState.ItemCount;
if (anchorPosition >= itemCount)
{
return(markerLine);
}
LayoutState.View anchor = state.GetView(anchorPosition);
state.CacheView(anchorPosition, anchor.view);
if (anchor.LayoutParams.FirstPosition != sd.firstPosition)
{
return(markerLine);
}
int firstContentPosition = sd.hasHeader ? sd.firstPosition + 1 : sd.firstPosition;
// Ensure the anchor is the first item in the row.
int col = (anchorPosition - firstContentPosition) % mNumColumns;
for (int i = 1; i <= col; i++)
{
// Detach and scrap attached items in this row, so we can re-lay them again. The last
// child view in the index can be the header so we just skip past it if it last.
for (int j = 1; j <= mLayoutManager.ChildCount; j++)
{
View child = mLayoutManager.GetChildAt(mLayoutManager.ChildCount - j);
if (mLayoutManager.GetPosition(child) == anchorPosition - i)
{
markerLine = mLayoutManager.GetDecoratedTop(child);
mLayoutManager.DetachAndScrapViewAt(j, state.recycler);
break;
}
LayoutManager.LayoutParams lp = (LayoutManager.LayoutParams)child.LayoutParameters;
if (lp.FirstPosition != sd.firstPosition)
{
break;
}
}
}
anchorPosition = anchorPosition - col;
// Lay out rows to end.
for (int i = anchorPosition; i < itemCount; i += mNumColumns)
{
if (markerLine >= leadingEdge)
{
break;
}
LayoutState.View view = state.GetView(i);
if (view.LayoutParams.FirstPosition != sd.firstPosition)
{
state.CacheView(i, view.view);
break;
}
int rowHeight = fillRow(markerLine, i, LayoutManager.Direction.END, true, sd, state);
markerLine += rowHeight;
}
return(markerLine);
}
/// <summary>
/// Measure view. A view is given an area as wide as a single column with an undefined height.
/// </summary>
/// <param name="child"> View to measure. </param>
/// <param name="sd"> Section data. </param>
private void MeasureChild(LayoutState.View child, SectionData sd)
{
int widthOtherColumns = (mNumColumns - 1) * mColumnWidth;
mLayoutManager.MeasureChildWithMargins(child.view, sd.marginStart + sd.marginEnd + widthOtherColumns, 0);
}
public override int FillToStart(int leadingEdge, int markerLine, int anchorPosition, SectionData sd, LayoutState state)
{
int firstContentPosition = sd.hasHeader ? sd.firstPosition + 1 : sd.firstPosition;
// Check to see if we have to adjust for minimum section height. We don't if there is an
// attached non-header view in this section.
bool applyMinHeight = false;
for (int i = 0; i < mLayoutManager.ChildCount; i++)
{
View check = mLayoutManager.GetChildAt(0);
LayoutManager.LayoutParams checkParams = (LayoutManager.LayoutParams)check.LayoutParameters;
if (checkParams.FirstPosition != sd.firstPosition)
{
applyMinHeight = true;
break;
}
if (!checkParams.isHeader)
{
applyMinHeight = false;
break;
}
}
// _ _ ^ a b
int col = (anchorPosition - firstContentPosition) % mNumColumns;
for (int i = 1; i < mNumColumns - col; i++)
{
// Detach and scrap attached items in this row, so we can re-lay them again. The last
// child view in the index can be the header so we just skip past it if it last.
for (int j = 0; j < mLayoutManager.ChildCount; j++)
{
View child = mLayoutManager.GetChildAt(j);
LayoutManager.LayoutParams lp = (LayoutManager.LayoutParams)child.LayoutParameters;
if (lp.FirstPosition != sd.firstPosition)
{
break;
}
if (mLayoutManager.GetPosition(child) == anchorPosition + i)
{
mLayoutManager.DetachAndScrapViewAt(j, state.recycler);
break;
}
}
}
// Ensure the anchor is the first item in the row.
int columnAnchorPosition = anchorPosition - col;
// Work out offset to marker line by measuring rows from the end. If section height is less
// than min height, then adjust marker line and then lay out items.
int measuredPositionsMarker = -1;
int sectionHeight = 0;
int minHeightOffset = 0;
if (applyMinHeight)
{
for (int i = columnAnchorPosition; i >= 0; i -= mNumColumns)
{
LayoutState.View check = state.GetView(i);
state.CacheView(i, check.view);
LayoutManager.LayoutParams checkParams = check.LayoutParams;
if (checkParams.FirstPosition != sd.firstPosition)
{
break;
}
int rowHeight = 0;
for (int j = 0; j < mNumColumns && i + j <= anchorPosition; j++)
{
LayoutState.View measure = state.GetView(i + j);
state.CacheView(i + j, measure.view);
LayoutManager.LayoutParams measureParams = measure.LayoutParams;
if (measureParams.FirstPosition != sd.firstPosition)
{
break;
}
if (measureParams.isHeader)
{
continue;
}
MeasureChild(measure, sd);
rowHeight = Math.Max(rowHeight, mLayoutManager.GetDecoratedMeasuredHeight(measure.view));
}
sectionHeight += rowHeight;
measuredPositionsMarker = i;
if (sectionHeight >= sd.minimumHeight)
{
break;
}
}
if (sectionHeight < sd.minimumHeight)
{
minHeightOffset = sectionHeight - sd.minimumHeight;
markerLine += minHeightOffset;
}
}
// Lay out rows to end.
for (int i = columnAnchorPosition; i >= 0; i -= mNumColumns)
{
if (markerLine - minHeightOffset < leadingEdge)
{
break;
}
LayoutState.View rowAnchor = state.GetView(i);
state.CacheView(i, rowAnchor.view);
LayoutManager.LayoutParams lp = rowAnchor.LayoutParams;
if (lp.isHeader || lp.FirstPosition != sd.firstPosition)
{
break;
}
bool measureRowItems = !applyMinHeight || i < measuredPositionsMarker;
int rowHeight = fillRow(markerLine, i, LayoutManager.Direction.START, measureRowItems, sd, state);
markerLine -= rowHeight;
}
return(markerLine);
}