如何在Swift3x的条形图上的Bar上方实现轨迹球和访问标签

您好开发人员我正在开发项目,我已经使用了danielgindi/Charts第三方库,现在我面临的挑战是我需要提供一个跟踪球,如图中最高点的图像所示.如何才能实现这一点？ ？或者如何访问BarChart上方的值,我想在最高峰(20.0)上打印其他内容,如"E"？

不幸的是,没有办法在条形图上方的值处设置图像而不是String或Double.但是,我们可以访问上面的值,请访问提到的链接. https://github.com/danielgindi/Charts/issues/2126

class ViewController: UIViewController {
    var chartData = BarChartData()
    var months: [String]!
    var unitsSold = [Double]()
 weak var valueFormatter: IValueFormatter?
   @IBOutlet var viewForChart: BarChartView!
override func viewDidLoad() {
        super.viewDidLoad()
valueFormatter = self

        mOnths= ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
        unitsSold = [20.0, 4.0, 6.0, 3.0, 12.0, 16.0, 4.0, 18.0, 2.0, 4.0, 5.0, 4.0]

 setChart(dataEntryX: months, dataEntryY: unitsSold)
}

    func setChart(dataEntryX forX:[String],dataEntryY forY: [Double]) {
        viewForChart.noDataText = "You need to provide data for the chart."
        var dataEntries:[BarChartDataEntry] = []
        for i in 0..

在类之上或之外添加扩展名

extension ViewController: IValueFormatter {
    func stringForValue(_ value: Double, entry: ChartDataEntry, dataSetIndex: Int, viewPortHandler: ViewPortHandler?) -> String {
        print(value)
        //logic to print string at required point or value
        switch value {

        case 20.0: return ""
        default: return ""
        }
    }
}