Question

您好我正在尝试向图表点添加点击事件，但是当我点击图表“对象引用未设置为对象的实例”时，我收到以下错误

这是我的代码

Private Sub Chart1_Click(sender As Object, e As System.EventArgs) Handles Chart1.Click
    Try
        Dim pointindex As Integer
        If result.ChartElementType = ChartElementType.DataPoint Then
            pointindex = result.PointIndex
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Sub

Private Sub Form1_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
    result = Chart1.HitTest(e.X, e.Y)
End Sub

Answer 1

如果鼠标光标位于控件上方，则控件将接收事件但不接收表单（对于解决方法，请参阅此问题：Winforms : Intercepting Mouse Event on Main Form first, not on Controls）。

因此Form1_MouseDown无法触发，result仍然Nothing Chart1_Click。

解决方法可能如下所示：

Private Sub Chart1_Click(sender As Object, e As System.EventArgs) Handles Chart1.Click
    Try
        Dim pointindex As Integer
        Dim result As HitTestResult
        result = Chart1.HitTest(Cursor.Position.X, Cursor.Position.Y)
        If result.ChartElementType = ChartElementType.DataPoint Then
            pointindex = result.PointIndex
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Sub

vb.net图表控制点onclick事件

1 个答案: