In This Topic
Knob indicators are visualized by radial gauges and extend the functionality of the NValueIndicator class. Therefore knob indicators have the same behavior as the NMarkerValueIndicator and the NNeedleValueIndicator indicators, with extensions specific to the the knob visualization.
Creating a Knob Indicator
In order to create a knob indicator you must first create an instance of the NKnobIndicator class and then add it to the Indicators collection of the radial gauge. The following code snippet creates a simple radial gauge with a knob:
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nChartControl1.Panels.Clear();
// create a radial gauge
NRadialGaugePanel radialGauge = new NRadialGaugePanel();
nChartControl1.Panels.Add(radialGauge);
radialGauge.CapStyle.Visible = false;
radialGauge.BeginAngle = -225;
radialGauge.SweepAngle = 270;
// modify the scale
NGaugeAxis axis = (NGaugeAxis)radialGauge.Axes[0];
NLinearScaleConfigurator scale = axis.ScaleConfigurator as NLinearScaleConfigurator;
scale.SetPredefinedScaleStyle(PredefinedScaleStyle.Presentation);
// add knob
NKnobIndicator knobIndicator = new NKnobIndicator();
knobIndicator.OffsetFromScale = new NLength(-2);
radialGauge.Indicators.Add(knobIndicator);
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| Visual Basic |
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NChartControl1.Panels.Clear()
' create a radial gauge
Dim radialGauge As New NRadialGaugePanel
NChartControl1.Panels.Add(radialGauge)
radialGauge.CapStyle.Visible = False
radialGauge.BeginAngle = -225
radialGauge.SweepAngle = 270
' modify the scale
Dim axis As NGaugeAxis = CType(radialGauge.Axes(0), NGaugeAxis)
Dim scale As NLinearScaleConfigurator = CType
axis.ScaleConfigurator, NLinearScaleConfigurator)
Scale.SetPredefinedScaleStyle(PredefinedScaleStyle.Presentation)
' add knob
Dim knobIndicator As New NKnobIndicator()
knobIndicator.OffsetFromScale = New NLength(-2)
radialGauge.Indicators.Add(knobIndicator)
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Knob Elements
Each knob element consists of several parts as shown the following picture:
The inner and outer rim style are controlled through the InnerRimStyle and OuterRimStyle properties of the NKnobIndicator respectively. For a detailed description of the options avialable for the rim style check the "Rim Style" section below. The knob marker position is determined by the Value property of the indicator (as with all indicators that extend the NValueIndicator class) and its shape is specified as a smart shape
Rim Style
Both the inner and the outer rim styles of the knob are controlled through an instance of the NCircularRimStyle class. The rim style has several properties allowing you to customize its pattern.
Rim Pattern
You can change the rim pattern with the help of the Pattern property of the rim style. On the picture above the outer rim style uses RoundHandle rim pattern and the inner rim uses Circle respectively. The following table lists the available pattern options:
| Pattern |
Description |
| Bolt |
The appearance of the rim resembles a bolt. |
| Circle |
The rim is circular. On the picture above the inner rim style uses this pattern. |
| EdgeHandle |
The appearance of the rim resembles a handle with "edges". |
| EdgeHandleSmall |
Same as edge handle except the dips between edges are smaller. |
| RoundHandle |
The appearance of the rim resembles a handle with round edges. On the picture above the outer rim style uses this pattern. |
| RoundHandleSmall |
Same as RoundHandle except the the dips between the edges are smaller. |
Repeat Count
For all rim patterns except circle you can also control the PatternRepeatCount property allowing you specify how many times the pattern will be repeated around the knob edge. On the picture above the outer rim uses a repeat count of 6.
Radius Offset
The Offset property allows you to configure the distance of the rim pattern from the rim of the knob.
The following code snippet shows how to modify these properties:
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// create the knob
NKnobIndicator knobIndicator = new NKnobIndicator();
// offset the knob from the scale
knobIndicator.OffsetFromScale = new NLength(-2);
// configure the outer rim style
knobIndicator.OuterRimStyle.Pattern = CircularRimPattern.RoundHandleSmall;
knobIndicator.OuterRimStyle.PatternRepeatCount = 8;
knobIndicator.OuterRimStyle.Offset = new NLength(2);
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| Visual Basic |
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' create the knob
Dim knobIndicator As New NKnobIndicator()
' offset the knob from the scale
knobIndicator.OffsetFromScale = New NLength(-2)
' configure the outer rim style
knobIndicator.OuterRimStyle.Pattern = CircularRimPattern.RoundHandleSmall
knobIndicator.OuterRimStyle.PatternRepeatCount = 8
knobIndicator.OuterRimStyle.Offset = New NLength(2)
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Related Examples
Windows forms: Gauge Gallery\Gauges\Indicators\Knob Indicator
Web forms: Gauge Gallery\Gauges\Indicators\Knob Indicator
