Coreplot line chart line is not visible

问题

I tried to make a line graph with core plot but I have a problem. There is no line in the simulator though the number(for:...) function (last lines) works and the data is retrieved. I've been trying to do this for 60 hours and I don't know what's wrong here. And there are no more details.

Here is my code:

import UIKit
import CorePlot

class dottedLine: UIViewController {
    @IBOutlet var hostView: CPTGraphHostingView!

    var plot: CPTScatterPlot!

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        initPlot()
    }

    let xValues: [NSNumber] = [1,2,3,4]
    let yValues: [NSNumber] = [1,5,4,3]

    func initPlot() {
        configureHostView()
        configureGraph()
        configureChart()
        configureAxes()
    }

    func configureHostView() {
        hostView.allowPinchScaling = false
    }

    func configureGraph() {
        // 1 - Create the graph
        let graph = CPTXYGraph(frame: hostView.bounds)
        graph.plotAreaFrame?.masksToBorder = false
        hostView.hostedGraph = graph

        // 2 - Configure the graph
        //graph.apply(CPTTheme(named: CPTThemeName.plainWhiteTheme))
        //graph.fill = CPTFill(color: CPTColor.clear())
        graph.paddingBottom = 30.0
        graph.paddingLeft = 30.0
        graph.paddingTop = 0.0
        graph.paddingRight = 0.0

        // 3 - Set up styles
        let titleStyle = CPTMutableTextStyle()
        titleStyle.color = CPTColor.black()
        titleStyle.fontName = "HelveticaNeue-Bold"
        titleStyle.fontSize = 16.0
        titleStyle.textAlignment = .center
        graph.titleTextStyle = titleStyle

        let title = "Just title"
        graph.title = title
        graph.titlePlotAreaFrameAnchor = .top
        graph.titleDisplacement = CGPoint(x: 0.0, y: -16.0)

        // 4 - Set up plot space
        let xMin = 0.0
        let xMax = 5.0
        let yMin = 0.0
        let yMax = 15.0
        guard let plotSpace = graph.defaultPlotSpace as? CPTXYPlotSpace else { return }
        plotSpace.xRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(xMin), lengthDecimal: CPTDecimalFromDouble(xMax - xMin))
        plotSpace.yRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(yMin), lengthDecimal: CPTDecimalFromDouble(yMax - yMin))
    }

    func configureChart() {
        // 1 - Set up the plot
        plot = CPTScatterPlot()

        // 2 - Set up style
        let plotLineStile = CPTMutableLineStyle()
        plotLineStile.lineWidth = 1
        plotLineStile.lineColor = CPTColor.black()
        plot.dataLineStyle = plotLineStile

        // 3- Add plots to graph
        guard let graph = hostView.hostedGraph else { return }
        plot.dataSource = self
        plot.delegate = self
        graph.add(plot, to: graph.defaultPlotSpace)
    }

    func configureAxes() {
    }
}

extension dottedLine: CPTScatterPlotDataSource, CPTScatterPlotDelegate {
    func numberOfRecords(for plot: CPTPlot) -> UInt {
        // number of points
        return UInt(xValues.count)
    }

    func scatterPlot(_ plot: CPTScatterPlot, plotSymbolWasSelectedAtRecord idx: UInt, with event: UIEvent) {
    }

    func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any? {
        switch CPTScatterPlotField(rawValue: Int(field))! {
        case .X:
            return 2 as NSNumber
        case .Y:
            return 3 as NSNumber
        }
    }
}

回答1:

I checked your code.

func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any? {
    switch CPTScatterPlotField(rawValue: Int(field))! {
    case .X:
        return 2 as NSNumber
    case .Y:
        return 3 as NSNumber
    }
}

According to the above CPTScatterPlotDataSource of your code, the data you are giving for each and every record is the same data point which is (X: 2, Y: 3). Given that you are giving the same point for all the records, your final dataset for the scatterplot will be:

[
  (X: 2, Y: 3),
  (X: 2, Y: 3),
  (X: 2, Y: 3),
  (X: 2, Y: 3)
]

You can't get a line with this data set, it will just be a point.

Try giving different data for different records, you will see a line. You can see the example below to understand

func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any? {
    switch CPTScatterPlotField(rawValue: Int(field))! {
    case .X:
        let xVal = self.xValues[Int(record)] 
        return xVal
    case .Y:
        let yVal = self.yValues[Int(record)]
        return yVal
    }
}

来源：https://stackoverflow.com/questions/46306033/coreplot-line-chart-line-is-not-visible