Question

我有一个LineSeries图表。通过series.IsSelectionEnabled = true;当我将鼠标移动到点上时，我可以选择该节点。但是当鼠标没有完全超过该点但是在它附近（上方或下方）时，我怎么能这样做呢？感谢。

PS：还有一件事。如何在鼠标悬停时更改列的颜色，以便用户可以分辨出他/她要选择哪一列。

Answer 1

我已使用单个LineSeries创建了图表示例。您可以单击绘图中的任意位置，并选择最近的点。

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>

代码隐藏：

    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，即使您在距离任何图表点很远的地方点击，此图表也会选择最近的点。如果它不是预期的行为，您可以取消注释这些行并设置任何数字（以像素为单位）：

//Uncomment if it is necessary to have some kind of sensitive area
if (minLength > 50)
    return null;

我写过评论，但如果事情不清楚，你可以问我，我会解释。

在Silverlight Toolkit图表中选择最近的点

1 个答案: