Question

我有一个图表，我希望用户在指针位于点上时看到值。通过在页面finding the value of the points in a chart中使用digEmAll的帮助，我可以编写以下代码：

Point? prevPosition = null; 
ToolTip tooltip = new ToolTip();  

void chart1_MouseMove(object sender, MouseEventArgs e) 
{     
    var pos = e.Location;     
    if (prevPosition.HasValue && pos == prevPosition.Value)         
        return;     
    tooltip.RemoveAll();     
    prevPosition = pos;     
    var results = chart1.HitTest(pos.X, pos.Y, false, ChartElementType.PlottingArea);     
    foreach (var result in results)     
    {         
        if (result.ChartElementType == ChartElementType.PlottingArea)         
        {            
            chart1.Series[0].ToolTip = "X=#VALX, Y=#VALY";          
        }    
    } 
}

通过上面的代码，当指针接近一个系列时，用户可以看到这些值。但是现在我怎样才能让用户只在指针时看到这些值点点？我换了

int k = result.PointIndex;
if (k >= 0)
{
    chart1.Series[0].Points[k].ToolTip = "X=#VALX, Y=#VALY";
}

而不是

chart1.Series[0].ToolTip = "X=#VALX, Y=#VALY";

解决我的问题。但这没用。

Answer 1

您应该以这种方式修改代码：

Point? prevPosition = null;
ToolTip tooltip = new ToolTip();

void chart1_MouseMove(object sender, MouseEventArgs e)
{
    var pos = e.Location;
    if (prevPosition.HasValue && pos == prevPosition.Value)
        return;
    tooltip.RemoveAll();
    prevPosition = pos;
    var results = chart1.HitTest(pos.X, pos.Y, false,
                                    ChartElementType.DataPoint);
    foreach (var result in results)
    {
        if (result.ChartElementType == ChartElementType.DataPoint)
        {
            var prop = result.Object as DataPoint;
            if (prop != null)
            {
                var pointXPixel = result.ChartArea.AxisX.ValueToPixelPosition(prop.XValue);
                var pointYPixel = result.ChartArea.AxisY.ValueToPixelPosition(prop.YValues[0]);

                // check if the cursor is really close to the point (2 pixels around the point)
                if (Math.Abs(pos.X - pointXPixel) < 2 &&
                    Math.Abs(pos.Y - pointYPixel) < 2)
                {
                    tooltip.Show("X=" + prop.XValue + ", Y=" + prop.YValues[0], this.chart1,
                                    pos.X, pos.Y - 15);
                }
            }
        }
    }
}

我的想法是检查鼠标是否非常接近这一点，例如它周围有2个像素（因为在该点上实际上不太可能完全）并且在这种情况下显示工具提示。

Here's a complete working example.

Answer 2

我会采取这个解决方案：

添加自定义工具提示事件处理程序：

 this.chart1.GetToolTipText += this.chart1_GetToolTipText;

实现事件处理程序：

  private void chart1_GetToolTipText(object sender, ToolTipEventArgs e)
  {
     // Check selected chart element and set tooltip text for it
     switch (e.HitTestResult.ChartElementType)
     {
        case ChartElementType.DataPoint:
           var dataPoint = e.HitTestResult.Series.Points[e.HitTestResult.PointIndex];
           e.Text = string.Format("X:\t{0}\nY:\t{1}", dataPoint.XValue, dataPoint.YValues[0]);
           break;
     }
  }

Answer 3

将以下内容视为比工具提示更好的选择...使用图表控件的标签功能。

DataPoint _prevPoint;
void chart1_MouseMove(object sender, MouseEventArgs e)
{
    // this if statement clears the values from the previously activated point.
    if (_prevPoint) {
        _prevPoint.MarkerStyle = MarkerStyle.None;
        _prevPoint.IsValueShownAsLabel = false;
    }

    var result = chart1.HitTest(e.X, e.Y, ChartElementType.DataPoint);
    if (result.ChartElementType == ChartElementType.DataPoint)
    {
        var prop = result.Object as DataPoint;
        if (prop != null)
        {
            prop.IsValueShownAsLabel = true;
            prop.MarkerStyle = MarkerStyle.Star4;
        }
    }
}

我已经对此进行了测试，并且我目前正在使用它。由于它在图表上也显示了标记，所以在图表上有很多点非常好。

当鼠标在点上时，查看图表点的值

3 个答案: