CircularGaugeHitInfo.Needle Property

Gets a needle which is located under the test point.

Namespace: DevExpress.Xpf.Gauges

Assembly: DevExpress.Xpf.Gauges.v20.2.dll

Declaration

public ArcScaleNeedle Needle { get; }
Public ReadOnly Property Needle As ArcScaleNeedle

Property Value

Type Description
ArcScaleNeedle

An ArcScaleNeedle object that is the needle located under the test point.

Remarks

Use the Needle property to access the needle located under the test point (if the CircularGaugeHitInfo.InNeedle property returns true).

If CircularGaugeHitInfo.InNeedle is false, the Needle property returns null (Nothing in Visual Basic).

Examples

This example demonstrates how to show a tooltip with the current value of a needle on a circular gauge.

To do this, it is necessary to handle the MouseMove and MouseLeave events for the CircularGaugeControl object and obtain the current mouse position on a scale via the CircularGaugeControl.CalcHitInfo method. After that, if the mouse pointer hovers over the needle, it becomes possible to invoke the tooltip that displays the current needle's value.

Note that this approach is applicable to only those gauge elements whose ValueIndicatorBase.IsHitTestVisible property is set to True (this is the default option). If the IsHitTestVisible property is set to False, this element is excluded from the hit-testing algorithm. To explore this behavior in action, mark and unmark the "Show tooltips for a needle" CheckEdit (whose check state is bound to the needle's IsHitTestVisible property). So, the unmarked CheckEdit's state means that tooltips are not displayed for a needle.

View Example

Imports Microsoft.VisualBasic
Imports System.Windows
Imports System.Windows.Controls.Primitives
Imports System.Windows.Input
Imports DevExpress.Xpf.Gauges

Namespace DXGauges_ShowTooltips

    Partial Public Class MainWindow
        Inherits Window
        Public Sub New()
            InitializeComponent()
        End Sub


        Private Sub circularGaugeControl1_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs)
                Dim hitInfo As CircularGaugeHitInfo = circularGaugeControl1.CalcHitInfo(e.GetPosition(circularGaugeControl1))

            If hitInfo.InNeedle Then
                tooltip_text.Text = "Value: " & hitInfo.Needle.Value.ToString("n2")
                tooltip.Placement = PlacementMode.Mouse

                tooltip.IsOpen = True
            Else
                tooltip.IsOpen = False
            End If

        End Sub

        Private Sub circularGaugeControl1_MouseLeave(ByVal sender As Object, ByVal e As MouseEventArgs)
            tooltip.IsOpen = False
        End Sub

    End Class
End Namespace
See Also