Charts: How to set colors of left and right axis labels in LineChartView?

Question

My graph is using custom IAxisValueFormatters to set the left and right axis labels (below). I've tried using the labelTextColor properties on left and right axis (below) but they're not changing the label's font color.

class myViewController {

    func initalizeGraph() {

        //omitted for brevity

        let leftYAxisValueFormatter = SpeedAndHRLeftYAxisValueFormatter(measurementSystem: measurementSystem)
        lineChartView.leftAxis.labelTextColor = iPhoneThemeColor1
        lineChartView.leftAxis.valueFormatter = leftYAxisValueFormatter

        let rightYAxisValueFormatter = SpeedAndHRRightYAxisValueFormatter()
        lineChartView.rightAxis.labelTextColor = iPhoneThemeColor2
        lineChartView.rightAxis.valueFormatter = rightYAxisValueFormatter
    }
}

class SpeedAndHRLeftYAxisValueFormatter: IAxisValueFormatter {
    //left side is speed

    //multiplu value x 40 (.5 * x = 20?)
    var measurementSystem: MeasurementSystem

    init(measurementSystem: MeasurementSystem) {
        self.measurementSystem = measurementSystem
    }

    func stringForValue(_ value: Double, axis: AxisBase?) -> String {

        let intValue = Int(value * 40)
        var suffixString = ""

        switch measurementSystem {
        case .US:
            suffixString =  "mph"
        case .Metric:
            suffixString = "km/h"
        }

        return "\(intValue)" + " " + suffixString
    }
}

class SpeedAndHRRightYAxisValueFormatter: IAxisValueFormatter {
    //right side is HR

    func stringForValue(_ value: Double, axis: AxisBase?) -> String {

        let intValue = Int(value * 210)

        return "\(intValue)" + " " + "bpm"
    }
}

Answer 1

You have to add following code in viewDidLoad() method. This is working perfactly for me in one of my project.

override func viewDidLoad() {

    let leftYAxisValueFormatter = SpeedAndHRLeftYAxisValueFormatter(measurementSystem: measurementSystem)
    lineChartView.leftAxis.valueFormatter = leftYAxisValueFormatter
    lineChartView.leftAxis.labelTextColor = iPhoneThemeColor1

    let rightYAxisValueFormatter = SpeedAndHRRightYAxisValueFormatter()
    lineChartView.rightAxis.valueFormatter = rightYAxisValueFormatter
    lineChartView.rightAxis.labelTextColor = iPhoneThemeColor2
}

Also, update you code for class create as follow:

@objc(LineChartFormatter)
class SpeedAndHRRightYAxisValueFormatter:NSObject, IAxisValueFormatter {
    ....
    //Your Code
    ....
}

@objc(LineChartFormatter)
class SpeedAndHRLeftYAxisValueFormatter:NSObject, IAxisValueFormatter {
    ....
    //Your Code
    ....
}

I hope this will help you.