ios - 如何使用核心图在方法 numberForPlot 中将时间作为 xAxis 数据值传递？

Question

我需要创建“心率与时间”图表。在 xAxis 中，我显示的时间格式为“HH:mm:ss”，在 y 轴上显示其十进制值。我的代码如下:

图的数据源:

     var graphData:[(String,Double)] = []
let data = ("17:56:35",Double(65))
            let data1 = ("18:04:13",Double(95))
            let data2 = ("18:8:35",Double(25))
            self.graphData.append(data)
            self.graphData.append(data1)
            self.graphData.append(data2)

设置图形和绘制数据代码:

func setGraph() {
    let tts = CPTMutableTextStyle()
    tts.fontSize = 75.0
    tts.color = CPTColor(CGColor: UIColor.blackColor().CGColor)
    tts.fontName = "HelveticaNeue-Bold"
    self.graph.titleTextStyle = tts

    self.graph.title = "Heart Rate vs Time"

    self.graph.applyTheme(CPTTheme(named:kCPTPlainWhiteTheme))
    let plotSpace = graph.defaultPlotSpace as! CPTXYPlotSpace!

    plotSpace.allowsUserInteraction = false

    let xRange = plotSpace.xRange.mutableCopy() as! CPTMutablePlotRange
    xRange.locationDouble = Double(0)
    xRange.lengthDouble = Double(1000)
    plotSpace.xRange = xRange

    let yRange = plotSpace.yRange.mutableCopy() as! CPTMutablePlotRange
    yRange.locationDouble = Double(0)
    yRange.lengthDouble = Double(210)
    plotSpace.yRange = yRange

    graph.addPlotSpace(plotSpace)

    graph.plotAreaFrame!.paddingTop    = 0
    graph.plotAreaFrame!.paddingRight  = 0
    graph.plotAreaFrame!.paddingBottom = graphOffset
    graph.plotAreaFrame!.paddingLeft   = graphOffset
    graph.plotAreaFrame!.masksToBorder = false

    // Grid line styles
    let majorLineStyle          = CPTMutableLineStyle()
    majorLineStyle.lineWidth    = 0.75
    majorLineStyle.lineColor    = CPTColor.redColor()

    let minorLineStyle          = CPTMutableLineStyle()
    minorLineStyle.lineWidth    = 0.25
    minorLineStyle.lineColor    = CPTColor.blackColor()

    //Axis Line colors
    let axisLineStyle           = CPTMutableLineStyle()
    axisLineStyle.lineWidth     = 2.0
    axisLineStyle.lineColor     = CPTColor.blackColor()

    //Axis Label colors
    let labelTextStyle              = CPTMutableTextStyle()
    labelTextStyle.textAlignment    = CPTTextAlignment.Left
    labelTextStyle.color            = CPTColor.blackColor()

    //Axis title color
    let titleTextStyle              = CPTMutableTextStyle()
    titleTextStyle.textAlignment    = CPTTextAlignment.Left
    titleTextStyle.color            = CPTColor.blackColor()
    titleTextStyle.fontSize         = 15

    let dataSourceLinePlot = CPTScatterPlot()
    let lineStyle               = CPTMutableLineStyle()
    lineStyle.lineWidth         = 3.0
    lineStyle.lineColor         = CPTColor.blueColor()
    dataSourceLinePlot.dataLineStyle = lineStyle
    dataSourceLinePlot.identifier    = kPlotIdentifier
    //        dataSourceLinePlot.dataSource    = self


    let xts = CPTMutableTextStyle()
    xts.color = CPTColor(componentRed: 255.0, green: 255.0, blue: 255.0, alpha: 1.0)


    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "HH:mm:ss"
    let timeformatter = CPTTimeFormatter(dateFormatter: dateFormatter)
    timeformatter.referenceDate = NSDate()

    let axisSet = graph.axisSet as! CPTXYAxisSet!

    let xAxis = axisSet.xAxis as CPTXYAxis!
    xAxis.axisTitle = CPTAxisTitle(text: "Elapsed Time", textStyle: xts)
    xAxis.labelFormatter = timeformatter
    xAxis.majorGridLineStyle = majorLineStyle
    xAxis.minorGridLineStyle = minorLineStyle
    xAxis.majorIntervalLength = NSNumber(double: 60.0)

    let yAxis = axisSet.yAxis as CPTXYAxis!
    yAxis.axisTitle = CPTAxisTitle(text: "Heart Rate", textStyle: xts)
    let axisFormatter = NSNumberFormatter()
    axisFormatter.maximumFractionDigits = 0
    axisFormatter.minimumIntegerDigits = 1
    yAxis.labelFormatter = axisFormatter
    yAxis.titleOffset = 35.0
    yAxis.majorIntervalLength = 20
    yAxis.majorGridLineStyle = majorLineStyle
    yAxis.minorGridLineStyle = minorLineStyle


    graph.addPlot(dataSourceLinePlot)
    self.IBviewGraph.hostedGraph = self.graph

}

绘制数据:

func setGraphData() {

     dispatch_sync(dispatch_get_main_queue(), {

    let plot = CPTScatterPlot()
    plot.dataSource = self

    let actualPlotStyle = plot.dataLineStyle!.mutableCopy() as! CPTMutableLineStyle
    actualPlotStyle.lineWidth = 2.0
    actualPlotStyle.lineColor = CPTColor(CGColor: (UIColor.yellowColor().CGColor))
    plot.dataLineStyle = actualPlotStyle
    plot.interpolation = .Linear

    self.graph.addPlot(plot)

    })
}

数据源方法

 func numberOfRecordsForPlot(plot: CPTPlot) -> UInt {
    return 3
}

 func numberForPlot(plot: CPTPlot, field: UInt, recordIndex: UInt) -> AnyObject?{

    var num = NSNumber()
    let index = Int(recordIndex)
    switch field {
    case 0://xaxis

        return graphData[index].0

    case 1://yaxis
        return graphData[index].1
    default:
        break
    }
    print("coordintes = ",num)
   return num
}

我的图表被淹没了，但只有 yAxis 点是正确的，它没有考虑 xAxis 值，因此因为这些点在图表中的位置错误。我认为我在 xAxis 的方法 numberForPlot 中传递的值是错误的，但不知道如何传递它。给我一些解决方案。

Answer 1

graphData 数组中的 x 值是字符串。 Core Plot 期望数据源为每个索引返回一个数值。它从时间字符串中读取小时并将其用于 x 值。

x 轴配置为显示 0 到 1,000 范围内的数字。因此，您需要将时间数据转换为该范围内的数字。跟踪用于格式化轴标签的引用日期(即将其存储在实例变量中)，并使用它来将时间数据转换为引用日期的偏移量(以秒为单位)。