C# 当鼠标在点上时查看图表点的值
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see values of chart points when the mouse is on points
提问by Asma Good
I have a chart and I want the user to see the values when the pointer is on the points. By using digEmAll's help in the page finding the value of the points in a chart,I could write the following code:
我有一个图表，我希望用户在指针位于点上时看到值。通过在页面中使用 digEmAll 的帮助查找图表中点的值，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";
}
}
}
by the above code,the user can see the values when the pointer is near toa series.But now How can I let the user to see the values only when the pointer is onthe points? I replaced
通过上面的代码，当指针靠近一个系列时，用户可以看到值。但是现在我怎样才能让用户只有当指针在点上时才能看到值？我换了
int k = result.PointIndex;
if (k >= 0)
{
chart1.Series[0].Points[k].ToolTip = "X=#VALX, Y=#VALY";
}
instead of
代替
chart1.Series[0].ToolTip = "X=#VALX, Y=#VALY";
to solve my problem.But It wasn't usefull.
解决我的问题。但它没有用。
采纳答案by digEmAll
You should modify the code in this way:
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);
}
}
}
}
}
The idea is to check if the mouse is very close to the point e.g. 2pixels around it (because is really unlikely to be exactlyon the point) and show the tooltip in that case.
这个想法是检查鼠标是否非常接近该点，例如2它周围的像素（因为实际上不太可能正好在该点上）并在这种情况下显示工具提示。
回答by jreichert
I would take this solution:
我会采取这个解决方案：
Add custom tooltip event handler:
添加自定义工具提示事件处理程序：
this.chart1.GetToolTipText += this.chart1_GetToolTipText;
Implement event handler:
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;
}
}
回答by iQueue
Consider the following as a possible better option than tooltips...use the label feature of the chart control.
考虑以下可能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;
}
}
}
I've tested this and i'm using it currently. It's very nice on charts with a lot of points since it shows the marker on the chart as well.
我已经对此进行了测试，目前正在使用它。它在具有很多点的图表上非常好，因为它也在图表上显示了标记。
