[英]Select the nearest point in a Silverlight Toolkit chart
我有一个LineSeries图表。 按系列series.IsSelectionEnabled = true;
当我将鼠标移到这些点上时,可以选择该节点。 但是,当鼠标不完全在该点上但它在它附近(上方或下方)时,我该怎么办? 谢谢。
PS:还有一件事。 当鼠标悬停在列上时,如何更改其颜色,以便用户可以知道他/她将选择哪个列。
我用单个LineSeries
创建了图表示例。 您可以在图上的任意位置单击,然后将选择最近的点。
XAML(将ItemsSource
属性和其他属性更改为您的属性):
<Charting:Chart MouseLeftButtonDown="Chart_MouseLeftButtonDown">
<Charting:Chart.Series>
<Charting:LineSeries IsSelectionEnabled="True" ItemsSource="..." ... />
</Charting:Chart.Series>
</Charting:Chart>
后台代码:
private void Chart_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var chart = sender as Chart;
//In my example the line series is the first item of the chart series
var line = (LineSeries)chart.Series[0];
//Find the nearest point on the LineSeries
var newPoint = e.GetPosition(line);
var selectIndex = this.FindNearestPointIndex(line.Points, newPoint);
if (selectIndex != null)
{
//Select a real item from the items source
var source = line.ItemsSource as IList;
line.SelectedItem = source[selectIndex.Value];
}
}
private int? FindNearestPointIndex(PointCollection points, Point newPoint)
{
if (points == null || !points.Any())
return null;
//c^2 = a^2+b^2
Func<Point, Point, double> getLength = (p1, p2) => Math.Sqrt(Math.Pow(p1.X - p2.X, 2) + Math.Pow(p1.Y - p2.Y, 2));
//Create the collection of points with more information
var items = points.Select((p,i) => new { Point = p, Length = getLength(p, newPoint), Index = i });
var minLength = items.Min(item => item.Length);
//Uncomment if it is necessary to have some kind of sensitive area
//if (minLength > 50)
// return null;
//The index of the point with min distance to the new point
return items.First(item => item.Length == minLength).Index;
}
正如我所说的,即使您单击距离任何图表点很远的地方,该图表也会选择最近的点。 如果这不是预期的行为,则可以取消注释这些行,并以像素为单位设置任何数字:
//Uncomment if it is necessary to have some kind of sensitive area
if (minLength > 50)
return null;
我已经写了评论,但是如果不清楚,您可以提出要求,我会解释。
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