How can I add a Marker on ios-charts?

Question

I'm creating an iOS app using Objective-C and I need to use ios-charts.

Now I'm facing a problem that I couldn't find the way to add a Marker to my graphView.

Also, I need to change the YAxis data set by user action, but I have no idea how to implement this feature.

Thank you for your help.

Answer 1

Add this code and this BalloonMarker class in the Charts->Components folder:

var charts = LineChartView()

let marker:BalloonMarker = BalloonMarker(color: UIColor(red: 93/255, green: 186/255, blue: 215/255, alpha: 1), font: UIFont(name: "Helvetica", size: 12)!, textColor: UIColor.white, insets: UIEdgeInsets(top: 7.0, left: 7.0, bottom: 25.0, right: 7.0))
 marker.minimumSize = CGSize(width: 75.0, height: 35.0)//CGSize(75.0, 35.0)
charts.marker = marker

//BalloonMarker class

import Foundation
import CoreGraphics
import UIKit


open class BalloonMarker: MarkerImage
{
    open var color: UIColor?
    open var arrowSize = CGSize(width: 15, height: 11)
    open var font: UIFont?
    open var textColor: UIColor?
    open var insets = UIEdgeInsets()
    open var minimumSize = CGSize()

    fileprivate var label: String?
    fileprivate var _labelSize: CGSize = CGSize()
    fileprivate var _paragraphStyle: NSMutableParagraphStyle?
    fileprivate var _drawAttributes = [String : AnyObject]()

    public init(color: UIColor, font: UIFont, textColor: UIColor, insets: UIEdgeInsets)
    {
        super.init()

        self.color = color
        self.font = font
        self.textColor = textColor
        self.insets = insets

        _paragraphStyle = NSParagraphStyle.default.mutableCopy() as? NSMutableParagraphStyle
        _paragraphStyle?.alignment = .center
    }

    open override func offsetForDrawing(atPoint point: CGPoint) -> CGPoint
    {
        let size = self.size
        var point = point
        point.x -= size.width / 2.0
        point.y -= size.height
        return super.offsetForDrawing(atPoint: point)
    }

    open override func draw(context: CGContext, point: CGPoint)
    {
        guard let label = label else { return }

        let offset = self.offsetForDrawing(atPoint: point)
        let size = self.size

        var rect = CGRect(
            origin: CGPoint(
                x: point.x + offset.x,
                y: point.y + offset.y),
            size: size)
        rect.origin.x -= size.width / 2.0
        rect.origin.y -= size.height

        context.saveGState()

        if let color = color
        {
            context.setFillColor(color.cgColor)
            context.beginPath()
            context.move(to: CGPoint(
                x: rect.origin.x,
                y: rect.origin.y))
            context.addLine(to: CGPoint(
                x: rect.origin.x + rect.size.width,
                y: rect.origin.y))
            context.addLine(to: CGPoint(
                x: rect.origin.x + rect.size.width,
                y: rect.origin.y + rect.size.height - arrowSize.height))
            context.addLine(to: CGPoint(
                x: rect.origin.x + (rect.size.width + arrowSize.width) / 2.0,
                y: rect.origin.y + rect.size.height - arrowSize.height))
            context.addLine(to: CGPoint(
                x: rect.origin.x + rect.size.width / 2.0,
                y: rect.origin.y + rect.size.height))
            context.addLine(to: CGPoint(
                x: rect.origin.x + (rect.size.width - arrowSize.width) / 2.0,
                y: rect.origin.y + rect.size.height - arrowSize.height))
            context.addLine(to: CGPoint(
                x: rect.origin.x,
                y: rect.origin.y + rect.size.height - arrowSize.height))
            context.addLine(to: CGPoint(
                x: rect.origin.x,
                y: rect.origin.y))
            context.fillPath()
        }

        rect.origin.y += self.insets.top
        rect.size.height -= self.insets.top + self.insets.bottom

        UIGraphicsPushContext(context)

        label.draw(in: rect, withAttributes: _drawAttributes)

        UIGraphicsPopContext()

        context.restoreGState()
    }

    open override func refreshContent(entry: ChartDataEntry, highlight: Highlight)
    {
        setLabel(String(entry.y))
    }

    open func setLabel(_ newLabel: String)
    {
        label = newLabel

        _drawAttributes.removeAll()
        _drawAttributes[NSFontAttributeName] = self.font
        _drawAttributes[NSParagraphStyleAttributeName] = _paragraphStyle
        _drawAttributes[NSForegroundColorAttributeName] = self.textColor

        _labelSize = label?.size(attributes: _drawAttributes) ?? CGSize.zero

        var size = CGSize()
        size.width = _labelSize.width + self.insets.left + self.insets.right
        size.height = _labelSize.height + self.insets.top + self.insets.bottom
        size.width = max(minimumSize.width, size.width)
        size.height = max(minimumSize.height, size.height)
        self.size = size
    }
}