如何在条形图的顶部显示条形图值？

Question

我正在使用iOS图表库在我的应用程序中添加自定义图表，我创建了一个条形图，这是我的要求，由于某种原因，我已经反转了图表所以问题是条形图所基于的值创建的数据显示在图表上，我想在条形图的顶部显示这些值。这是我用于创建图形的代码

@IBOutlet var barChartView: BarChartView!

let unitsSold = [20, 4, 6, 3, 12, 50, 25, 57, 60, 28, 17, 47]
let unitsBought = [10.0, 14.0, 60.0, 13.0, 2.0, 10.0, 15.0, 18.0, 25.0, 05.0, 10.0, 19.0]
let xaxisValue: [String] = ["Jan", "Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]

//MARK:- View Life Cycle -
override func viewDidLoad() {
    super.viewDidLoad()

    setupView()
}


//MARK:- General Methods -
func setupView() {

    //legend
    let legend = barChartView.legend
    legend.enabled = true
    legend.horizontalAlignment = .right
    legend.verticalAlignment = .bottom
    legend.orientation = .horizontal
    legend.drawInside = true
    legend.yOffset = 10.0;
    legend.xOffset = 10.0;
    legend.yEntrySpace = 0.0;
    legend.textColor = UIColor.white

    // Y - Axis Setup
    let yaxis = barChartView.leftAxis
    yaxis.spaceTop = 0.35
    yaxis.axisMinimum = 0
    yaxis.drawGridLinesEnabled = false
    yaxis.labelTextColor = UIColor.white
    yaxis.axisLineColor = UIColor.white
    yaxis.labelPosition = .insideChart
    yaxis.enabled = false
   // YAxis leftAxis = barChart.getAxisLeft();
    barChartView.rightAxis.enabled = false

    // X - Axis Setup
    let xaxis = barChartView.xAxis
    let formatter = CustomLabelsXAxisValueFormatter()//custom value formatter
    formatter.labels = self.xaxisValue
    xaxis.valueFormatter = formatter

    xaxis.drawGridLinesEnabled = false
    xaxis.labelPosition = .top
    xaxis.labelTextColor = UIColor.white
    xaxis.centerAxisLabelsEnabled = true
    xaxis.axisLineColor = UIColor.white
    xaxis.granularityEnabled = true
    xaxis.enabled = true

    barChartView.delegate = self
    barChartView.noDataText = "You need to provide data for the chart."
    barChartView.noDataTextColor = UIColor.white
    barChartView.chartDescription?.textColor = UIColor.clear

    setChart()
}

func setChart() {
    barChartView.noDataText = "Loading...!!"
    var dataEntries: [BarChartDataEntry] = []
    var dataEntries1: [BarChartDataEntry] = []

    for i in 0..<self.xaxisValue.count {

        let dataEntry = BarChartDataEntry(x: Double(i) , y: Double(self.unitsSold[i]))
        dataEntries.append(dataEntry)

        let dataEntry1 = BarChartDataEntry(x: Double(i) , y: Double(self.unitsBought[i]))
        dataEntries1.append(dataEntry1)

    }

    let chartDataSet = BarChartDataSet(values: dataEntries, label: "Sold")
    let chartDataSet1 = BarChartDataSet(values: dataEntries1, label: "Bought")

    let dataSets: [BarChartDataSet] = [chartDataSet,chartDataSet1]
    chartDataSet.colors = [UIColor(red: 0/255, green: 255/255, blue: 0/255, alpha: 0.5)]
    chartDataSet1.colors = [UIColor(red: 255/255, green: 0/255, blue: 0/255, alpha: 0.8)]


    let chartData = BarChartData(dataSets: dataSets)

    let groupSpace = 0.4
    let barSpace = 0.02
    let barWidth = 0.2

    chartData.barWidth = barWidth
    chartData.setDrawValues(true)
    barChartView.xAxis.axisMinimum = 0.0
    barChartView.xAxis.axisMaximum = 0.0 + chartData.groupWidth(groupSpace: groupSpace, barSpace: barSpace) * Double(self.xaxisValue.count)

    chartData.groupBars(fromX: 0.0, groupSpace: groupSpace, barSpace: barSpace)
    barChartView.xAxis.granularity = barChartView.xAxis.axisMaximum / Double(self.xaxisValue.count)
    barChartView.drawValueAboveBarEnabled = true
    barChartView.keepPositionOnRotation = true
    barChartView.clipValuesToContentEnabled = true
    barChartView.data = chartData
    barChartView.getAxis(.left).inverted = true

    barChartView.notifyDataSetChanged()
    barChartView.setVisibleXRangeMaximum(4)
    barChartView.animate(yAxisDuration: 1.0, easingOption: .linear)
    chartData.setValueTextColor(UIColor.yellow)
}

这是上面代码的输出

我想将标签显示为下图（当图形处于倒置状态时）

请让我知道如何实现这一目标。

Answer 1

我认为目前使用Charts不可能。这些值在BarChartRender.swift函数中的drawValues(context: CGContext)中呈现，但总是在条形图上方。如果左轴反转，则不会在下方渲染它们。如果你想要这种行为，你应该自己实现它改变函数的这部分代码：

drawValue(
    context: context,
    value: formatter.stringForValue(
    val,
    entry: e,
    dataSetIndex: dataSetIndex,
    viewPortHandler: viewPortHandler),
    xPos: x,
    yPos: val >= 0.0
    ? (rect.origin.y + rect.size.height + posOffset)
    : (rect.origin.y + negOffset), // Those lines should do what you're trying to achieve
    font: valueFont,
    align: .center,
    color: dataSet.valueTextColorAt(j))