iOS Charting Documentation - SciChart iOS Charts SDK v3.x

SCILegendModifier

In SciChart, the easiest way to add a Legend onto a chart is to use a SCILegendModifier

Legend Modifier

NOTE: Example of the SCILegendModifier usage can be found in the SciChart iOS Examples Suite as well as on GitHub:

The SCILegendModifier class exposes several configurational properties. Please find them explained in the table below:

Feature Description
SCILegendModifier.position Allows to specify SCIAlignment for the Legend.
SCILegendModifier.margins Allows to specify margins UIEdgeInsets for the Legend.
SCILegendModifier.orientation Determines orientation of the Legend. Can be either Horizontal or Vertical.
SCILegendModifier.showLegend Allows to hide or show the Legend.
SCILegendModifier.showCheckBoxes Determines whether to show visibility checkboxes for every RenderableSeries in the Legend or not. These allow hiding or showing their corresponding RenderableSeries.
SCILegendModifier.showSeriesMarkers Determines whether to show colored markers for every RenderableSeries in the Legend or not.
SCILegendModifier.sourceMode Allows to specify which RenderableSeries should appear in the Legend, e.g. Visible, Selected, etc. Series. Other will be ignored by the modifier. Expects a member of the SCISourceMode enumeration.

Adding the SCILegendModifier to a Chart

Any Chart Modifier can be added to a SCIChartSurface via theISCIChartSurface.chartModifiers property and SCILegendModifier is no difference.

// Assume a surface has been created and configured somewhere id<ISCIChartSurface> surface; // Create a Modifier SCILegendModifier *legendModifier = [SCILegendModifier new]; legendModifier.position = SCIAlignment_Top | SCIAlignment_Left; legendModifier.margins = UIEdgeInsetsMake(16, 16, 16, 16); legendModifier.sourceMode = SCISourceMode_AllSeries; legendModifier.orientation = SCIOrientationHorizontal; // Add the modifier to the surface [self.surface.chartModifiers add:legendModifier];
// Assume a surface has been created and configured somewhere let surface: ISCIChartSurface // Create a Modifier let legendModifier = SCILegendModifier() legendModifier.position = [.left, .top] legendModifier.margins = UIEdgeInsets(top: 16, left: 16, bottom: 16, right: 16) legendModifier.sourceMode = .allVisibleSeries legendModifier.orientation = .horizontal // Add the modifier to the surface self.surface.chartModifiers.add(legendModifier)
// Assume a surface has been created and configured somewhere IISCIChartSurface surface; // Create a Modifier var legendModifier = new SCILegendModifier(); legendModifier.Position = SCIAlignment.Top | SCIAlignment.Left; legendModifier.Margins = new UIEdgeInsets(16, 16, 16, 16); legendModifier.SourceMode = SCISourceMode.AllSeries; legendModifier.Orientation = SCIOrientation.Horizontal; // Add the modifier to the surface Surface.ChartModifiers.Add(legendModifier);

NOTE: To learn more about features available, Chart Modifier APIs article.

Placing Legend outside the Chart

To place a Legend outside the chart you will need to create the following objects:

  1. SCIChartLegend programmatically or using Interface Builder.
  2. SCILegendDataSource instance.
  3. SCILegendModifier instance with useAutoPlacement = false parameter using the -[SCILegendModifier initWithLegend:dataSource:useAutoPlacement:] initializer.

NOTE: By passing false to useAutoPlacement argument you indicate that you want to place SCIChartLegend instance manually, in this case - outside the Chart Surface.

While placing a Legend you might want to use your custom constraints. There are two most common approaches to define Legend frame:

Resizing according to the legend content

By default, we calculate Legend size according to its content. To achieve this, we use some under the hood calculations and apply constraints with priority 800-801. If you want to allow the Legend to be resized according to its content, a priority of your width and height constraints should be lower than 800.

As an example, let’s assume that you want to place a Legend with the following requirements:

  • it should be placed at the Top and Leading of the parent view
  • size should be calculated according to its content.
  • your SCIChartSurface should be placed trailing to the Legend and fill all available space.

To achieve this you need to add leading and top constraints with a priority higher than 801, e.g. 1000, trailing and bottom constraints with a priority less than 800, e.g. 500 to the Legend.

Please see an example below where we create SCIChartLegend and SCIChartSurface programmatically:

// Create Chart Surface SCIChartSurface *surface = [SCIChartSurface new]; [self addSubview:surface]; // Create surface constraints surface.translatesAutoresizingMaskIntoConstraints = NO; NSLayoutConstraint *topSurfaceConstraint = [surface.topAnchor constraintEqualToAnchor:self.safeAreaLayoutGuide.topAnchor]; NSLayoutConstraint *trailingSurfaceConstraint = [surface.trailingAnchor constraintEqualToAnchor: self.trailingAnchor]; NSLayoutConstraint *bottomSurfaceConstraint = [surface.bottomAnchor constraintEqualToAnchor: self.bottomAnchor]; // Create a legend SCIChartLegend *legend = [SCIChartLegend new]; [self addSubview:legend]; // Create legend constraints legend.translatesAutoresizingMaskIntoConstraints = NO; NSLayoutConstraint *leadingLegendConstraint = [legend.leadingAnchor constraintEqualToAnchor: self.leadingAnchor]; NSLayoutConstraint *topLegendConstraint = [legend.topAnchor constraintEqualToAnchor: self.safeAreaLayoutGuide.topAnchor]; NSLayoutConstraint *trailingLegendConstraint = [legend.trailingAnchor constraintEqualToAnchor: surface.leadingAnchor]; // By setting constraint priority to value lower than 800 you indicate that the legend will ignore this constraint and calculate its width or height automatically. Hence these constraints will be ignored, adding them here is optional. NSLayoutConstraint *bottomLegendConstraint = [legend.bottomAnchor constraintEqualToAnchor: self.bottomAnchor]; bottomLegendConstraint.priority = 500; NSLayoutConstraint *widthLegendConstraint = [legend.widthAnchor constraintEqualToConstant:300]; widthLegendConstraint.priority = 500; [legend addConstraint:widthLegendConstraint]; // Add constraints to a superview [self addConstraints:@[topSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint, leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint/*, bottomLegendConstraint*/]]; // Create a dataSource SCISeriesInfoLegendDataSource *dataSource = [[SCISeriesInfoLegendDataSource alloc] initWithLegend:legend]; // Create a modifier SCILegendModifier *legendModifier = [[SCILegendModifier alloc] initWithLegend:legend dataSource:dataSource useAutoPlacement:NO]; // Add the modifier to the surface [self.surface.chartModifiers add:legendModifier];
// Create Chart Surface let surface = SCIChartSurface() self.addSubview(surface) // Create surface constraints surface.translatesAutoresizingMaskIntoConstraints = false let topSurfaceConstraint = surface.topAnchor.constraint(equalTo: self.safeAreaLayoutGuide.topAnchor) let trailingSurfaceConstraint = surface.trailingAnchor.constraint(equalTo: self.trailingAnchor) let bottomSurfaceConstraint = surface.bottomAnchor.constraint(equalTo: self.bottomAnchor) // Create a legend let legend = SCIChartLegend() self.addSubview(legend) // Create legend constraints legend.translatesAutoresizingMaskIntoConstraints = false let leadingLegendConstraint = legend.leadingAnchor.constraint(equalTo: self.leadingAnchor) let topLegendConstraint = legend.topAnchor.constraint(equalTo: self.safeAreaLayoutGuide.topAnchor) let trailingLegendConstraint = legend.trailingAnchor.constraint(equalTo: surface.leadingAnchor) // By setting constraint priority to value lower than 800 you indicate that the legend will ignore this constraint and calculate its width or height automatically. Hence these constraints will be ignored, adding them here is optional. let bottomLegendConstraint = legend.bottomAnchor.constraint(equalTo: self.bottomAnchor) bottomLegendConstraint.priority = UILayoutPriority(rawValue: 500) let widthLegendConstraint = legend.widthAnchor.constraint(equalToConstant: 300) widthLegendConstraint.priority = UILayoutPriority(rawValue: 500) legend.addConstraint(widthLegendConstraint) // Add constraints to a superview self.addConstraints([topSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint, leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint, bottomLegendConstraint]) // Create a dataSource guard let dataSource = SCISeriesInfoLegendDataSource(legend: legend) else { return } // Create a modifier let legendModifier = SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: false) // Add the modifier to the surface surface.chartModifiers.add(legendModifier)
// Create Chart Surface var surface = new SCIChartSurface(); View.AddSubview(surface); // Create surface constraints surface.TranslatesAutoresizingMaskIntoConstraints = false; var topSurfaceConstraint = surface.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor); var trailingSurfaceConstraint = surface.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor); var bottomSurfaceConstraint = surface.BottomAnchor.ConstraintEqualTo(View.BottomAnchor); // Create a legend var legend = new SCIChartLegend(); View.AddSubview(legend); // Create legend constraints legend.TranslatesAutoresizingMaskIntoConstraints = false; var leadingLegendConstraint = legend.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor); var topLegendConstraint = legend.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor); var trailingLegendConstraint = legend.TrailingAnchor.ConstraintEqualTo(surface.LeadingAnchor); // By setting constraint priority to value lower than 800 you indicate that the legend will ignore this constraint and calculate its width or height automatically. Hence these constraints will be ignored, adding them here is optional. var bottomLegendConstraint = legend.BottomAnchor.ConstraintEqualTo(View.BottomAnchor); bottomLegendConstraint.Priority = 500; var widthLegendConstraint = legend.WidthAnchor.ConstraintEqualTo(300); widthLegendConstraint.Priority = 500; legend.AddConstraint(widthLegendConstraint); // Add constraints to a superview View.AddConstraints(new NSLayoutConstraint[] { topSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint, leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint, bottomLegendConstraint }); // Create a dataSource var dataSource = new SCISeriesInfoLegendDataSource(legend); // Create a modifier var legendModifier = new SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: false); // Add the modifier to the surface surface.ChartModifiers.Add(legendModifier);

This produces the following output: Legend Modifier

Fill all available space defined by the constraints

Sometimes you might want to place a legend as a normal view with a fixed width or height. To achieve this, the priority of all your constraints must be higher than 801.

As an example, let’s assume that you want to place a Legend with the following requirements:

  • at the top of the parent view with leading, top, trailing constraints
  • with fixed height equal to 70.
  • SCIChartSurface instance should be below and fill all available space.
  • in case the content of a Legend is bigger than its height user can scroll it as a normal collection view.

Please see the code on how to achieve that below:

// Create a legend SCIChartLegend *legend = [SCIChartLegend new]; [self addSubview:legend]; // Create legend constraints legend.translatesAutoresizingMaskIntoConstraints = NO; NSLayoutConstraint *leadingLegendConstraint = [legend.leadingAnchor constraintEqualToAnchor:self.leadingAnchor]; NSLayoutConstraint *topLegendConstraint = [legend.topAnchor constraintEqualToAnchor: self.safeAreaLayoutGuide.topAnchor]; NSLayoutConstraint *trailingLegendConstraint = [legend.trailingAnchor constraintEqualToAnchor: self.trailingAnchor]; NSLayoutConstraint *heightLegendConstraint = [legend.heightAnchor constraintEqualToConstant:70]; [legend addConstraint:heightLegendConstraint]; // Create Chart Surface SCIChartSurface *surface = [SCIChartSurface new]; [self addSubview:surface]; // Create surface constraints surface.translatesAutoresizingMaskIntoConstraints = NO; NSLayoutConstraint *topSurfaceConstraint = [surface.topAnchor constraintEqualToAnchor: legend.bottomAnchor]; NSLayoutConstraint *leadingSurfaceConstraint = [surface.leadingAnchor constraintEqualToAnchor: self.leadingAnchor]; NSLayoutConstraint *trailingSurfaceConstraint = [surface.trailingAnchor constraintEqualToAnchor: self.trailingAnchor]; NSLayoutConstraint *bottomSurfaceConstraint = [surface.bottomAnchor constraintEqualToAnchor: self.bottomAnchor]; // Add constraints to a superview [self addConstraints:@[leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint, topSurfaceConstraint, leadingSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint]]; // Create a dataSource SCISeriesInfoLegendDataSource *dataSource = [[SCISeriesInfoLegendDataSource alloc] initWithLegend:legend]; // Create a modifier SCILegendModifier *legendModifier = [[SCILegendModifier alloc] initWithLegend:legend dataSource:dataSource useAutoPlacement:NO]; // Add the modifier to the surface [self.surface.chartModifiers add:legendModifier];
// Create a legend let legend = SCIChartLegend() self.addSubview(legend) // Create legend constraints legend.translatesAutoresizingMaskIntoConstraints = false let leadingLegendConstraint = legend.leadingAnchor.constraint(equalTo: self.leadingAnchor) let topLegendConstraint = legend.topAnchor.constraint(equalTo: self.safeAreaLayoutGuide.topAnchor) let trailingLegendConstraint = legend.trailingAnchor.constraint(equalTo: self.trailingAnchor) let heightLegendConstraint = legend.heightAnchor.constraint(equalToConstant: 70) legend.addConstraint(heightLegendConstraint) // Create Chart Surface let surface = SCIChartSurface() self.addSubview(surface) // Create surface constraints surface.translatesAutoresizingMaskIntoConstraints = false let topSurfaceConstraint = surface.topAnchor.constraint(equalTo: legend.bottomAnchor) let leadingSurfaceConstraint = surface.leadingAnchor.constraint(equalTo: self.leadingAnchor) let trailingSurfaceConstraint = surface.trailingAnchor.constraint(equalTo: self.trailingAnchor) let bottomSurfaceConstraint = surface.bottomAnchor.constraint(equalTo: self.bottomAnchor) // Add constraints to a superview self.addConstraints([leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint, topSurfaceConstraint, leadingSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint]) // Create a dataSource guard let dataSource = SCISeriesInfoLegendDataSource(legend: legend) else { return } // Create a modifier let legendModifier = SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: false) // Add the modifier to the surface surface.chartModifiers.add(legendModifier)
// Create a legend var legend = new SCIChartLegend(); View.AddSubview(legend); // Create legend constraints legend.TranslatesAutoresizingMaskIntoConstraints = false; var leadingLegendConstraint = legend.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor); var topLegendConstraint = legend.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor); var trailingLegendConstraint = legend.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor); var heightLegendConstraint = legend.HeightAnchor.ConstraintEqualTo(70); legend.AddConstraint(heightLegendConstraint); // Create Chart Surface var surface = new SCIChartSurface(); View.AddSubview(surface); // Create surface constraints surface.TranslatesAutoresizingMaskIntoConstraints = false; var topSurfaceConstraint = surface.TopAnchor.ConstraintEqualTo(legend.BottomAnchor); var leadingSurfaceConstraint = surface.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor); var trailingSurfaceConstraint = surface.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor); var bottomSurfaceConstraint = surface.BottomAnchor.ConstraintEqualTo(View.BottomAnchor); // Add constraints to a superview View.AddConstraints(new NSLayoutConstraint[] { leadingLegendConstraint, topLegendConstraint, trailingLegendConstraint, topSurfaceConstraint, leadingSurfaceConstraint, trailingSurfaceConstraint, bottomSurfaceConstraint }); // Create a dataSource var dataSource = new SCISeriesInfoLegendDataSource(legend); // Create a modifier var legendModifier = new SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: false); // Add the modifier to the surface surface.ChartModifiers.Add(legendModifier);

This produces the following output: Legend Modifier

Create Legend with a custom item

To create a SCIChartLegend with custom items, you will need to create UICollectionView inheritor and pass it to SCILegendDataSource so we can prepare everything else for you. Read on to learn how to do that.

Create a Custom Legend Item

Your Custom Legend Item must inherit from UICollectionViewCell and conform to ISCILegendItem protocol. Also, it must be created in xib with reuseIdentifier = LegendItemReuseIdentifier.

Please see a simple example below:

// Assume that the CustomLegendItem.xib file is created somewhere in your project // CustomLegendItem.h #import <UIKit/UIKit.h> #import “ISCILegendItem.h” @interface CustomLegendItem : UICollectionViewCell @end // CustomLegendItem.m #import “CustomLegendItem.h” #import “SCISeriesInfo.h” @interface CustomLegendItem() @property (weak, nonatomic) IBOutlet UIView *markerView; @property (weak, nonatomic) IBOutlet UILabel *seriesNameLabel; @end @implementation CustomLegendItem - (void)bindSeriesInfoWith:(id)source legend:(id)legend { SCISeriesInfoCore *seriesInfo = (SCISeriesInfoCore *)source; self.seriesNameLabel.text = seriesInfo.seriesName; self.markerView.backgroundColor = seriesInfo.seriesColor; } @end
// Assume that the CustomLegendItem.xib file is created somewhere in your project import UIKit final class CustomLegendItem: UICollectionViewCell, ISCILegendItem { @IBOutlet private weak var markerView: UIView! @IBOutlet private weak var seriesNameLabel: UILabel! override var reuseIdentifier: String? { return LegendItemReuseIdentifier } // MARK: ISCILegendItem func bindSeriesInfo(with source: Any!, legend: ISCIChartLegend!) { guard let seriesInfo = source as? SCISeriesInfoCore else { return } markerView.backgroundColor = seriesInfo.seriesColor seriesNameLabel.text = seriesInfo.seriesName } }
// Assume that the CustomLegendItem.xib file is created somewhere in your project using System; using Foundation; using UIKit; using SciChart.iOS.Charting; namespace Xamarin.Examples.Demo.iOS { public partial class CustomLegendItem : UICollectionViewCell, IISCILegendItem { public static readonly NSString Key = new NSString(“CustomLegendItem”); public static readonly UINib Nib; static CustomLegendItem() { Nib = UINib.FromName(“CustomLegendItem”, NSBundle.MainBundle); } protected CustomLegendItem(IntPtr handle) : base(handle) { // Note: this .ctor should not contain any initialization logic. } public override NSString ReuseIdentifier => SCIChartLegend.LegendItemReuseIdentifier; public void bindSeriesInfo(NSObject source, IISCIChartLegend legend) { var seriesInfo = source as SCISeriesInfoCore; if (seriesInfo != null) { markerView.BackgroundColor = seriesInfo.SeriesColor; seriesNameLabel.Text = seriesInfo.SeriesName; } } } }

Adding a Legend with CustomItem to a Chart

To add a Legend with previously created Custom Legend Item you will need to do the following:

NOTE: By passing true or false to useAutoPlacement argument you indicate whether you want to place your SCIChartLegend instance manually, e.g. - inside or outside the Chart Surface.

Please see the code sample on how to do that below:

// Assume a surface has been created and configured somewhere ISCIChartSurface surface; // Create a legend SCIChartLegend *legend = [SCIChartLegend new]; // Create a dataSource with your custom legend item xib name. Assume a CustomLegendItem class has been created and configured somewhere SCISeriesInfoLegendDataSource *dataSource = [[SCISeriesInfoLegendDataSource alloc] initWithLegend:legend legendItemXibName:@“CustomLegendItem”]; // Create a modifier. // By passing `YES` to `useAutoPlacement` argument you indicate that you want to place Legend inside the Chart Surface. SCILegendModifier *legendModifier = [[SCILegendModifier alloc] initWithLegend:legend dataSource:dataSource useAutoPlacement:YES]; legendModifier.margins = UIEdgeInsetsMake(16, 16, 16, 16); legendModifier.position = SCIAlignment_Top | SCIAlignment_Left; // Add the modifier to the surface [self.surface.chartModifiers add:legendModifier];
// Assume a surface has been created and configured somewhere let surface: ISCIChartSurface // Create a legend let legend = SCIChartLegend() // Create a dataSource with your custom legend item xib name. Assume a CustomLegendItem class has been created and configured somewhere let dataSource = SCISeriesInfoLegendDataSource(legend: legend, legendItemXibName: “CustomLegendItem”) // Create a modifier. // By passing `true` to `useAutoPlacement` argument you indicate that you want to place Legend inside the Chart Surface. let legendModifier = SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: true) legendModifier.position = [.left, .top] legendModifier.margins = UIEdgeInsets(top: 16, left: 16, bottom: 16, right: 16) // Add the modifier to the surface surface.chartModifiers.add(legendModifier)
// Assume a surface has been created and configured somewhere SCIChartSurface surface; // Create a legend var legend = new SCIChartLegend(); // Create a dataSource with your custom legend item xib name. Assume a CustomLegendItem class has been created and configured somewhere var dataSource = new SCISeriesInfoLegendDataSource(legend: legend, legendItemXibName: “CustomLegendItem”); // Create a modifier. // By passing `true` to `useAutoPlacement` argument you indicate that you want to place Legend inside the Chart Surface. var legendModifier = new SCILegendModifier(legend: legend, dataSource: dataSource, useAutoPlacement: true); legendModifier.Position = SCIAlignment.Top | SCIAlignment.Left; legendModifier.Margins = new UIEdgeInsets(16, 16, 16, 16); // Add the modifier to the surface surface.ChartModifiers.Add(legendModifier);

This produces the following output: Legend Modifier