在Silverlight工具包图表中选择最近的点

问题描述

| 我有一个Lineseries图表。当我将鼠标移到这些点上时，通过

series.IsSelectionEnabled = true;

，可以选择该节点。但是，当鼠标不完全在该点上而是它在它附近（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，以便用户知道他/她将选择哪一列。     

解决方法

我创建了带有单个“ 1”的图表示例。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;

我已经写过评论，但是如果不清楚，您可以提问，我会解释。