How to render custom label colors for different xAxis labels?

Question

I'm creating a chart using Charts library to draw a combined chart in my app.

I succeeded in drawing the graph. Now I want to change the xAxis label text color of specific labels. The example was shown in the pic.

As in the picture I want to change the color of specific values for example 03/06 & 06/06. When I referred the library on github they told me to override the drawValues() function to achieve this. As I'm newbie to swift programming I don't know how to achieve this. Please guide me on how to achieve this task. Thanks in advance.

Answer 1

Inside the XAxisRenderer.swift (not the XAxisRendererHorizontalBarChart like the other answer suggested) add this list with your colors above the drawLabels function:

 let labelTextColorList = [UIColor.black, UIColor.red, UIColor.blue, UIColor.brown, UIColor.cyan, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black]

then replace the drawLabels function with this code:

 /// draws the x-labels on the specified y-position
open func drawLabels(context: CGContext, pos: CGFloat, anchor: CGPoint)
{
    guard
        let xAxis = self.axis as? XAxis,
        let viewPortHandler = self.viewPortHandler,
        let transformer = self.transformer
        else { return }

    #if os(OSX)
        let paraStyle = NSParagraphStyle.default().mutableCopy() as! NSMutableParagraphStyle
    #else
        let paraStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
    #endif
    paraStyle.alignment = .center

    //label attrs moved from here
    /*            let labelAttrs = [NSFontAttributeName: xAxis.labelFont,
     NSForegroundColorAttributeName: xAxis.labelTextColor,
     NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]
     */

    let labelRotationAngleRadians = xAxis.labelRotationAngle * ChartUtils.Math.FDEG2RAD

    let centeringEnabled = xAxis.isCenterAxisLabelsEnabled

    let valueToPixelMatrix = transformer.valueToPixelMatrix

    var position = CGPoint(x: 0.0, y: 0.0)

    var labelMaxSize = CGSize()

    if xAxis.isWordWrapEnabled
    {
        labelMaxSize.width = xAxis.wordWrapWidthPercent * valueToPixelMatrix.a
    }

    let entries = xAxis.entries

    for i in stride(from: 0, to: entries.count, by: 1)
    {

        //label attrs moved to here
        let labelAttrs: [String: NSObject]!

        if(i<labelTextColorList.count) {
            labelAttrs = [NSFontAttributeName: xAxis.labelFont,
                                  NSForegroundColorAttributeName: labelTextColorList[i],
                                  NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]
        }
        else {
            labelAttrs = [NSFontAttributeName: xAxis.labelFont,
                          NSForegroundColorAttributeName: xAxis.labelTextColor,
                          NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]

        }
        if centeringEnabled
        {
            position.x = CGFloat(xAxis.centeredEntries[i])
        }
        else
        {
            position.x = CGFloat(entries[i])
        }

        position.y = 0.0
        position = position.applying(valueToPixelMatrix)

        if viewPortHandler.isInBoundsX(position.x)
        {
            let label = xAxis.valueFormatter?.stringForValue(xAxis.entries[i], axis: xAxis) ?? ""

            let labelns = label as NSString

            if xAxis.isAvoidFirstLastClippingEnabled
            {
                // avoid clipping of the last
                if i == xAxis.entryCount - 1 && xAxis.entryCount > 1
                {
                    let width = labelns.boundingRect(with: labelMaxSize, options: .usesLineFragmentOrigin, attributes: labelAttrs, context: nil).size.width

                    if width > viewPortHandler.offsetRight * 2.0
                        && position.x + width > viewPortHandler.chartWidth
                    {
                        position.x -= width / 2.0
                    }
                }
                else if i == 0
                { // avoid clipping of the first
                    let width = labelns.boundingRect(with: labelMaxSize, options: .usesLineFragmentOrigin, attributes: labelAttrs, context: nil).size.width
                    position.x += width / 2.0
                }
            }

            drawLabel(context: context,
                      formattedLabel: label,
                      x: position.x,
                      y: pos,
                      attributes: labelAttrs,
                      constrainedToSize: labelMaxSize,
                      anchor: anchor,
                      angleRadians: labelRotationAngleRadians)
        }
    }
}

result: