用户控制图不显示数据点

Question

我已经实现了一个User Control类来扩展Chart类的功能。该图表将实时添加数据。 User Control类创建ChartArea，并将其添加到基础图表。它还添加了标题，图例和系列。我的问题是当我向图表系列添加新的数据点时，图表不会像在vanilla图表中那样更新以反映这一点。

User Control类包含一个子数据，用于向基础图表添加数据：

Chart1.Series(seriesName).Points.AddXY(xValue, yValue)

我已经模拟了一个数据源，并且可以验证系列中确实存在数据点。我试过在Chart1，ChartArea，Series和User Control类本身上调用invalidate（），refresh（）和/或update（）。我还在创建系列时立即向系列添加了数据点，但也没有出现。

我觉得我错过了一些简单的东西;为什么这些数据点没有出现？

相关代码：

（dataChart是与用户控件关联的图表）

Imports System.Windows.Forms.DataVisualization.Charting

Public Class ScrollChart
    Private _legendName As String = "defaultLegend"

    Private _chartSpan As Single = 10
    Private _xAxisFormat As String = "#.0"
    Private _yAxisFormat As String = "#.0"
    Private _xMajorInterval As Single = 1
    Private _xMinorInterval As Single = 0.5

    '...Property getters and setters omitted

    Public Sub New()
        ' This call is required by the designer.
        InitializeComponent()

        'Remove default chart objects
        dataChart.Legends.Clear()
        dataChart.Titles.Clear()
        dataChart.Annotations.Clear()
        dataChart.Series.Clear()
        dataChart.ChartAreas.Clear()
    End Sub

    Public Sub createChartArea(ByVal areaName As String, ByVal areaTitle As String, ByVal xAxisTitle As String, ByVal yAxisTitle As String)
        'Create new ChartArea
        Dim newArea As ChartArea = New ChartArea(areaName)

        'Add area title
        Dim chartTitle As Title = New Title(areaTitle)
        dataChart.Titles.Add(chartTitle)

        'Add area legend
        Dim areaLegend As Legend = New Legend(_legendName)
        areaLegend.Docking = Docking.Bottom
        dataChart.Legends.Add(areaLegend)

        'Set X axis defaults for scrolling
        newArea.AxisX.Minimum = 0
        newArea.AxisX.Maximum = _chartSpan
        newArea.AxisX.MajorGrid.Interval = _xMajorInterval
        newArea.AxisX.MinorGrid.Enabled = True
        newArea.AxisX.MinorGrid.Interval = _xMinorInterval
        newArea.AxisX.LabelStyle.Format = _xAxisFormat
        newArea.AxisX.IsStartedFromZero = False
        newArea.AxisX.Title = xAxisTitle

        'Set Y axis defaults for scrolling
        newArea.AxisY.Minimum = 0
        newArea.AxisY.Maximum = 1
        newArea.AxisY.MinorGrid.Enabled = True
        newArea.AxisY.LabelStyle.Format = _yAxisFormat
        newArea.AxisY.IsStartedFromZero = False
        newArea.AxisY.Title = yAxisTitle

        'Add to chart
        dataChart.ChartAreas.Add(newArea)
    End Sub

    Public Sub createChartSeries(ByVal areaName As String, ByVal seriesName As String, ByVal seriesTitle As String)
        'Create new Series
        Dim newSeries As Series = New Series(seriesName)

        'Add series legend
        newSeries.Legend = _legendName
        newSeries.LegendText = seriesTitle

        'Set defaults for scrolling
        newSeries.ChartType = SeriesChartType.Line
        newSeries.Color = Color.Red
        newSeries.ChartArea = areaName
        newSeries.MarkerColor = Color.Red

        'Add to chart
        dataChart.Series.Add(newSeries)
    End Sub

    Public Sub addData(ByVal seriesName As String, ByVal xValue As Single, ByVal yValue As Single)
        'Add new data point
        dataChart.Series(seriesName).Points.AddXY(xValue, yValue)

        'Remove oldest point if series is larger than the given chart span
        Dim newestX As Double = dataChart.Series(seriesName).Points.Last.XValue
        Dim oldestX As Double = dataChart.Series(seriesName).Points.First.XValue

        If ((newestX - oldestX) > _chartSpan) Then
            dataChart.Series(seriesName).Points.RemoveAt(0)
        End If

        'Redraw axis
        dataChart.ChartAreas(dataChart.Series(seriesName).ChartArea).RecalculateAxesScale()
    End Sub

    Private Sub ScrollChart_Resize(sender As Object, e As EventArgs) Handles Me.Resize
        'Resize chart to control size
        dataChart.Size = Size
    End Sub
End Class

测试表格中的类用法：

Public Class Form1
    Private dataSource As New MockDataSource(10, 0.5)
    Private startTime As Date = Date.Now

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ScrollChart1.createChartArea("area1", "Test Data", "Time (Seconds)", "Value (Unitless)")
        ScrollChart1.createChartSeries("area1", "series1", "Test Value")
    End Sub

    Private Sub pollTimer_Tick(sender As Object, e As EventArgs) Handles pollTimer.Tick
        Dim currentElapsed As Single = CSng((Date.Now - startTime).TotalSeconds)

        ScrollChart1.addData("series1", currentElapsed, dataSource.getRandomValue)
    End Sub
End Class