protected SKPoint[] CalculatePoints(IEnumerable <ChartValueItem> valueItems, SKRect frame, SKRect chart)
{
var result = new List <SKPoint>();
// Calculate how many values one y position is
var valueY = MaxValue / frame.Height;
// Calculate the width of one item (distance between items)
var itemWidth = chart.GetItemWidth(MaxItems);
for (int i = 0; i < valueItems.Count(); i++)
{
var entry = valueItems.ElementAt(i);
float x;
if (ChartValueItemsXPoints.FirstOrDefault(p => p.Item1.ToString() == entry.Tag.ToString())?.Item2 > 0)
{
x = ChartValueItemsXPoints.FirstOrDefault(p => p.Item1.ToString() == entry.Tag.ToString()).Item2;
}
else
{
x = chart.Left + (i * itemWidth);
}
// Calculate items y position with frame height (bottom to upper)
var y = frame.Top + (frame.Height - (entry.Value / valueY));
var point = new SKPoint(x, y);
result.Add(point);
entry.Point = point;
}
return(result.ToArray());
}
private void LineChart_PaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
if (ChartEntries?.Any() != true)
{
return;
}
var info = e.Info;
var canvas = e.Surface.Canvas;
canvas.Clear();
var frame = CreateFrame(info);
var chart = CreateChart(frame);
if (!IsInitialized)
{
// Makes slider first init in middle of frame
TouchedPoint = new SKPoint(frame.MidX, 0);
}
DrawVerticalLabels(canvas, frame, chart);
if (ChartEntries.Any(x => x.IsVisible))
{
CalculateChartValuesXPoints(chart);
DrawBackground(canvas, frame);
DrawInnerFrame(canvas, frame);
if (!string.IsNullOrEmpty(SelectedTag) && !isTouching)
{
var selectedTagPosition = ChartValueItemsXPoints.FirstOrDefault(x => x.Item1.ToString() == SelectedTag)?.Item2 ?? 0f;
TouchedPoint = new SKPoint(selectedTagPosition, 0f);
}
DrawSlider(canvas, frame, chart);
foreach (var entry in ChartEntries.Where(x => x.IsVisible).OrderByDescending(x => x.Items.Count()))
{
DrawLines(entry, canvas, CalculatePoints(entry.Items, frame, chart));
}
DrawHorizontalLabels(canvas, frame, chart);
// Get items on x axis
var valueItems = ChartEntries.GetChartValueItemFromX(chart.GetInsideXValue(TouchedPoint.X), frame, frame.GetItemWidth(MaxItems));
// Send selected items with command
SelectedValuesCommand?.Execute(new SelectedChartValueItemArgs
{
ChartValueItems = valueItems,
TouchedPoint = new SKPoint(chart.GetInsideXValue(TouchedPoint.X), TouchedPoint.Y)
});
DrawHorizontalLabel(valueItems?.FirstOrDefault()?.ChartValueItem, canvas, frame, chart);
DrawFrame(canvas, frame);
DrawSliderPoints(valueItems, canvas, chart);
}
else
{
DrawInnerFrame(canvas, frame);
DrawFrame(canvas, frame);
}
IsInitialized = true;
}