protected override void OnMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
if (View == null)
{
SetMeasuredDimension(0, 0);
return;
}
if (!View.IsVisible)
{
View.Measure(0, 0);
SetMeasuredDimension(0, 0);
return;
}
var width = widthMeasureSpec.GetSize();
var height = heightMeasureSpec.GetSize();
var measureWidth = width > 0 ? width : MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
var measureHeight = height > 0 ? height : MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
double?maxHeight = null;
if (MeasureHeight)
{
measureHeight = MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
}
else if (MatchWidth)
{
measureWidth = widthMeasureSpec;
}
else if (MatchHeight)
{
measureHeight = heightMeasureSpec;
maxHeight = heightMeasureSpec.GetSize();
}
var size = _shellContentView.Measure(measureWidth, measureHeight, null, (int?)maxHeight);
SetMeasuredDimension((int)size.Width, (int)size.Height);
}
protected override void OnMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
if (View == null)
{
SetMeasuredDimension(0, 0);
return;
}
if (!View.IsVisible)
{
View.Measure(0, 0);
SetMeasuredDimension(0, 0);
return;
}
var width = widthMeasureSpec.GetSize();
var height = heightMeasureSpec.GetSize();
var measureWidth = width > 0 ? MeasureSpecMode.Exactly.MakeMeasureSpec(width) : MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
var measureHeight = height > 0 ? MeasureSpecMode.Exactly.MakeMeasureSpec(height) : MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
double?maxHeight = null;
if (MeasureHeight)
{
measureHeight = MeasureSpecMode.Unspecified.MakeMeasureSpec(0);
}
else if (MatchWidth)
{
measureWidth = widthMeasureSpec;
}
else if (MatchHeight)
{
measureHeight = heightMeasureSpec;
maxHeight = heightMeasureSpec.GetSize();
}
var size = _shellContentView.Measure(measureWidth, measureHeight, null, (int?)maxHeight);
if (size.Height < this.MinimumHeight)
{
size = new Graphics.Size(size.Width, this.MinimumHeight);
}
DesiredSize = size;
var newHeight = size.Height;
if (_parentTopPadding > 0)
{
newHeight -= _parentTopPadding;
}
if (newHeight != size.Height)
{
// Android treats zero as unspecified so we need to set the height to at least 1.
// If there's a view that's able to squish/stretch then passing in zero will give it's stretched size
// but what we want here is the squished size.
var minHeightMeasureSpec = 1;
if (MinimumHeight > 0)
{
minHeightMeasureSpec = MinimumHeight;
}
if (newHeight <= 0)
{
newHeight = minHeightMeasureSpec;
}
// For collapse on scroll we need to know the minimum size the view can reach so we can set the minimum size
// on the headers container. This is the only way to get the AppBarLayout collapse behavior to stop producing
// offset changes once the header has reached the minimum size it can get to
MinimumSize = _shellContentView.Measure(measureWidth, MeasureSpecMode.Exactly.MakeMeasureSpec(minHeightMeasureSpec), null, (int?)maxHeight);
// If the offset of the appbar layout hasn't reached the minimum size then
// we use the new collapsed size to remeasure so everything is the correct size
if (newHeight > minHeightMeasureSpec)
{
size = _shellContentView.Measure(measureWidth, MeasureSpecMode.Exactly.MakeMeasureSpec((int)newHeight), null, (int?)maxHeight);
}
else
{
size = MinimumSize;
}
}
else
{
this.MinimumSize = new Graphics.Size((int)size.Width, this.MinimumHeight);
}
SetMeasuredDimension((int)size.Width, (int)size.Height);
}
