protected static MeasuredDimension ResolveSizeAndState(
float size,
MeasureSpec measureSpec,
MeasuredStateFlags childMeasuredState)
{
MeasuredDimension result = new MeasuredDimension();
MeasureMode specMode = measureSpec.Mode;
float specSize = measureSpec.Size;
switch (specMode)
{
case MeasureSpec.Unspecified:
result.Size = size;
break;
case MeasureSpec.AtMost:
if (specSize < size)
{
result.Size = specSize;
result.State |= MeasuredStateFlags.TooSmall;
}
else
{
result.Size = size;
}
break;
case MeasureSpec.Exactly:
result.Size = specSize;
break;
}
result.State |= childMeasuredState;
return(result);
}
protected override void OnMeasure(
MeasureSpec widthMeasureSpec,
MeasureSpec heightMeasureSpec)
{
var layoutProperties = this.LayoutProperties();
Size availableSize = new Size(
widthMeasureSpec.Size - layoutProperties.Padding.Left - layoutProperties.Padding.Right,
heightMeasureSpec.Size - layoutProperties.Padding.Top - layoutProperties.Padding.Bottom);
// Keep track of the space used by children
float usedWidth = 0;
float usedHeight = 0;
var remainingSize = availableSize;
MeasuredStateFlags childWidthState = MeasuredStateFlags.None;
MeasuredStateFlags childHeightState = MeasuredStateFlags.None;
int childCount = this.ChildCount;
for (int i = 0; i < childCount; i += 1)
{
var child = this.GetChildAt(i);
if (child.Hidden)
{
continue;
}
var layoutParams = (LayoutParams)child.LayoutParameters();
this.MeasureChildWithMarginsOverride(
child,
widthMeasureSpec,
usedWidth,
(layoutParams.Width == LayoutParams.MatchParent) ? LayoutParams.WrapContent : layoutParams.Width,
heightMeasureSpec,
usedHeight,
layoutParams.Height);
var childSize = GetChildUsedSizeWithMargins(child, layoutParams);
usedWidth += childSize.Width;
usedHeight = Math.Max(usedHeight, childSize.Height);
// Update the remaining size
remainingSize = new Size(
(float)Math.Max(0, availableSize.Width - usedWidth),
(float)Math.Max(0, availableSize.Height));
// Update the child state
childWidthState = CombineMeasuredStates(childWidthState, child.LayoutProperties().MeasuredSize.WidthState);
childHeightState = CombineMeasuredStates(childHeightState, child.LayoutProperties().MeasuredSize.HeightState);
}
// Calculate the total size used by children
Size usedSize = new Size(
(float)Math.Max(0, usedWidth),
(float)Math.Max(0, usedHeight));
// Default the final size to the size used by children
var finalSize = usedSize;
var dimensionX = ResolveSizeAndState(finalSize.Width, widthMeasureSpec, childWidthState);
var dimensionY = ResolveSizeAndState(finalSize.Height, heightMeasureSpec, childHeightState);
this.SetMeasuredSize(dimensionX, dimensionY);
}
protected static MeasuredStateFlags CombineMeasuredStates(
MeasuredStateFlags currentState,
MeasuredStateFlags newState)
{
return(currentState | newState);
}
