Annotations
3 Sep 2020 / 24 minutes to read
SFLinearGauge supports Annotations, which is used to mark the specific area of interest in the gauge area with texts, shapes, or images. You can add any number of annotations to the gauge.
Annotation
By using the View property of annotation object, you can specify the new element that needs to be displayed in the gauge area.
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.OffsetX = (float)0.6;
linearGaugeAnnotation.OffsetY = (float)0.4;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 200, 50);
textView.Text = "CPU Utilization";
textView.Font = UIFont.FromName("Helvetica", 20f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Positioning the annotation
You can place the annotation anywhere in gauge area by using the Offset or ScaleValue property.
Change annotation position by using offset
You can position the annotation anywhere in the linear gauge by using the OffsetX and OffsetY properties. It ranges from 0 to 1.
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.OffsetX = (float)0.6;
linearGaugeAnnotation.OffsetY = (float)0.6;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 200, 50);
textView.Text = "CPU Utilization";
textView.Font = UIFont.FromName("Helvetica", 20f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Change annotation position by using scale value
You can also place the annotation by specifying the ScaleValue property.
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.ScaleValue = 60;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 50, 70);
textView.Text = "60%";
textView.Font = UIFont.FromName("Helvetica-Bold", 20f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearScale.ScaleBarSize = 40;
linearScale.MinorTicksPerInterval = 1;
SFBarPointer barPointer = new SFBarPointer();
barPointer.Value = 60;
barPointer.Thickness = 20;
barPointer.CornerRadius = 10;
barPointer.CornerRadiusType = CornerRadiusType.End;
barPointer.Color = UIColor.FromRGB(249, 92, 133);
linearScale.Pointers.Add(barPointer);
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Set margin to the annotation
You can adjust the annotation by specifying the ViewMargin property in pixel, which adjusts the annotation element from its current position.
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.ScaleValue = 60;
linearGaugeAnnotation.ViewMargin = new CoreGraphics.CGPoint((float)10, (float)60);
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 50, 70);
textView.Text = "60%";
textView.Font = UIFont.FromName("Helvetica-Bold", 20f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearScale.ScaleBarSize = 40;
linearScale.MinorTicksPerInterval = 1;
SFBarPointer barPointer = new SFBarPointer();
barPointer.Value = 60;
barPointer.Thickness = 20;
barPointer.CornerRadius = 10;
barPointer.CornerRadiusType = CornerRadiusType.End;
barPointer.Color = UIColor.FromRGB(249, 92, 133);
linearScale.Pointers.Add(barPointer);
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Alignment of annotation
You can align the annotation using the HorizontalViewAlignment and VerticalViewAlignment properties.
Setting horizontal view alignment
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.ScaleValue = 60;
linearGaugeAnnotation.HorizontalViewAlignment = ViewAlignment.Start;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 150, 70);
textView.Text = "CPU Utilization";
textView.Font = UIFont.FromName("Helvetica-Bold", 15f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearScale.ScaleBarSize = 40;
linearScale.MinorTicksPerInterval = 1;
SFBarPointer barPointer = new SFBarPointer();
barPointer.Value = 60;
barPointer.Thickness = 20;
barPointer.CornerRadius = 10;
barPointer.CornerRadiusType = CornerRadiusType.End;
barPointer.Color = UIColor.FromRGB(249, 92, 133);
linearScale.Pointers.Add(barPointer);
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Setting vertical view alignment
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.ScaleValue = 60;
linearGaugeAnnotation.VerticalViewAlignment = ViewAlignment.Start;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 150, 70);
textView.Text = "CPU Utilization";
textView.Font = UIFont.FromName("Helvetica-Bold", 15f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
linearScale.ScaleBarSize = 40;
linearScale.MinorTicksPerInterval = 1;
SFBarPointer barPointer = new SFBarPointer();
barPointer.Value = 60;
barPointer.Thickness = 20;
barPointer.CornerRadius = 10;
barPointer.CornerRadiusType = CornerRadiusType.End;
barPointer.Color = UIColor.FromRGB(249, 92, 133);
linearScale.Pointers.Add(barPointer);
linearGauge.Scales.Add(linearScale);
this.View.AddSubview(linearGauge);
Setting scale index for annotation
You can set the index for the scale by using ScaleIndex
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.Header = new SFLinearLabel();
linearGauge.BackgroundColor = UIColor.White;
SFLinearGaugeAnnotation linearGaugeAnnotation = new SFLinearGaugeAnnotation();
linearGaugeAnnotation.OffsetX = (float)0.5;
linearGaugeAnnotation.OffsetY = (float)0.45;
linearGaugeAnnotation.ScaleIndex = 0;
UILabel textView = new UILabel();
textView.Frame = new CoreGraphics.CGRect(0, 0, 150, 70);
textView.Text = "CPU Utilization";
textView.Font = UIFont.FromName("Helvetica-Bold", 15f);
textView.TextColor = UIColor.Black;
linearGaugeAnnotation.View = textView;
linearGauge.Annotations.Add(linearGaugeAnnotation);
SFLinearGaugeAnnotation linearGaugeAnnotation1 = new SFLinearGaugeAnnotation();
linearGaugeAnnotation1.OffsetX = (float)0.5;
linearGaugeAnnotation1.OffsetY = (float)0.6;
linearGaugeAnnotation1.ScaleIndex = 1;
UILabel textView1 = new UILabel();
textView1.Frame = new CoreGraphics.CGRect(0, 0, 150, 70);
textView1.Text = "Thermometer";
textView1.Font = UIFont.FromName("Helvetica-Bold", 15f);
textView1.TextColor = UIColor.Black;
linearGaugeAnnotation1.View = textView1;
linearGauge.Annotations.Add(linearGaugeAnnotation1);
SFLinearScale linearScale = new SFLinearScale();
linearScale.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale.MajorTickSettings.Length = 12;
linearScale.MinorTickSettings.Length = 5;
linearScale.MinorTicksPerInterval = 1;
SFLinearScale linearScale1 = new SFLinearScale();
linearScale1.ScaleBarColor = UIColor.FromRGB(224, 224, 224);
linearScale1.LabelColor = UIColor.FromRGB(66, 66, 66);
linearScale1.MajorTickSettings.Length = 12;
linearScale1.MinorTickSettings.Length = 5;
linearScale1.MinorTicksPerInterval = 1;
linearScale1.Offset = 100;
linearGauge.Scales.Add(linearScale);
linearGauge.Scales.Add(linearScale1);
this.View.AddSubview(linearGauge);
Multiple annotations
You can add multiple annotations to the gauge as demonstrated below.
SFLinearGauge linearGauge = new SFLinearGauge();
linearGauge.BackgroundColor = UIColor.White;
linearGauge.Header = new SFLinearLabel();
SFLinearGaugeAnnotation annotation1 = new SFLinearGaugeAnnotation();
annotation1.ScaleValue = 15;
annotation1.ViewMargin = new CoreGraphics.CGPoint(0, 30);
UIImageView image1 = new UIImageView();
image1.Frame = new CoreGraphics.CGRect(0, 0, 30, 30);
image1.Image = UIImage.FromBundle("Low.png");
annotation1.View = image1;
SFLinearGaugeAnnotation annotation2 = new SFLinearGaugeAnnotation();
annotation2.ScaleValue = 45;
annotation2.ViewMargin = new CoreGraphics.CGPoint(0, 30);
UIImageView image2 = new UIImageView();
image2.Frame = new CoreGraphics.CGRect(0, 0, 30, 30);
image2.Image = UIImage.FromBundle("Moderate.png");
annotation2.View = image2;
SFLinearGaugeAnnotation annotation3 = new SFLinearGaugeAnnotation();
annotation3.ScaleValue = 75;
annotation3.ViewMargin = new CGPoint(0, 30);
UIImageView image3 = new UIImageView();
image3.Frame = new CGRect(0, 0, 30, 30);
image3.Image = UIImage.FromBundle("High.png");
annotation3.View = image3;
SFLinearGaugeAnnotation annotation4 = new SFLinearGaugeAnnotation();
annotation4.ScaleValue = 15;
annotation4.HorizontalViewAlignment = ViewAlignment.Center;
annotation4.ViewMargin = new CGPoint(0, 80);
UILabel label1 = new UILabel();
label1.Frame = new CGRect(0, 0, 30, 30);
label1.Text = "Low";
label1.Font = UIFont.FromName("Helvetica", 12f);
label1.TextColor = UIColor.FromRGB(48, 179, 45);
annotation4.View = label1;
SFLinearGaugeAnnotation annotation5 = new SFLinearGaugeAnnotation();
annotation5.ScaleValue = 45;
annotation5.HorizontalViewAlignment = ViewAlignment.Center;
annotation5.ViewMargin = new CGPoint(0, 80);
UILabel label2 = new UILabel();
label2.Text = "Moderate";
label2.Frame = new CGRect(0, 0, 60, 50);
label2.Font = UIFont.FromName("Helvetica", 12f);
label2.TextColor = UIColor.FromRGB(255, 221, 0);
annotation5.View = label2;
SFLinearGaugeAnnotation annotation6 = new SFLinearGaugeAnnotation();
annotation6.ScaleValue = 75;
annotation6.HorizontalViewAlignment = ViewAlignment.Center;
annotation6.ViewMargin = new CGPoint(0, 80);
UILabel label3 = new UILabel();
label3.Text = "High";
label3.Frame = new CGRect(0, 0, 30, 30);
label3.Font = UIFont.FromName("Helvetica", 12f);
label3.TextColor = UIColor.FromRGB(240, 62, 62);
annotation6.View = label3;
SFLinearGaugeAnnotation annotation7 = new SFLinearGaugeAnnotation();
annotation7.ScaleValue = 45;
annotation7.HorizontalViewAlignment = ViewAlignment.Center;
annotation7.ViewMargin = new CGPoint(0, -80);
UILabel label4 = new UILabel();
label4.Frame = new CGRect(0, 0, 130, 175);
label4.Text = "CPU Utilization";
//label4.Font = UIFont.FromName("Helvetica", 14f);
label4.TextColor = UIColor.Black;
annotation7.View = label4;
linearGauge.Annotations.Add(annotation1);
linearGauge.Annotations.Add(annotation2);
linearGauge.Annotations.Add(annotation3);
linearGauge.Annotations.Add(annotation4);
linearGauge.Annotations.Add(annotation5);
linearGauge.Annotations.Add(annotation6);
linearGauge.Annotations.Add(annotation7);
SFLinearScale scale = new SFLinearScale();
scale.Minimum = 0;
scale.Maximum = 90;
scale.ShowScaleLabel = false;
scale.MinorTicksPerInterval = 0;
scale.ScaleBarSize = 13;
scale.ShowTicks = false;
scale.ScaleBarColor = UIColor.Clear;
SFLinearTickSettings major = new SFLinearTickSettings();
major.Length = 0;
scale.MajorTickSettings = major;
SFLinearRange range1 = new SFLinearRange();
range1.StartValue = 0;
range1.EndValue = 30;
range1.StartWidth = 60;
range1.EndWidth = 60;
range1.Color = UIColor.FromRGB(48, 179, 45);
scale.Ranges.Add(range1);
SFLinearRange range2 = new SFLinearRange();
range2.StartValue = 30;
range2.EndValue = 60;
range2.StartWidth = 60;
range2.EndWidth = 60;
range2.Color = UIColor.FromRGB(255, 221, 0);
scale.Ranges.Add(range2);
SFLinearRange range3 = new SFLinearRange();
range3.StartValue = 60;
range3.EndValue = 90;
range3.StartWidth = 60;
range3.EndWidth = 60;
range3.Color = UIColor.FromRGB(240, 62, 62);
scale.Ranges.Add(range3);
linearGauge.Scales.Add(scale);
this.View.AddSubview(linearGauge);
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