ios Charts 3.0 - 使用图表对齐x标签(日期)

我很难将库图表(来自Daniel Gindi)从版本2(Swift 2.3)迁移到3(Swift 3).

基本上,我不能让x标签(日期)与相应的图正确对齐.

这是我之前在第2版中所拥有的:

在版本2中,我有第7天,第8天,第10天和第11天的值.所以我错过了中间的一天,但标签正确地与图表一起使用.

这是我在版本3中的内容:

在版本3中,x轴中的"标签"现在已被替换为double(对于日期,它是自1970年以来的timeInterval),并通过格式化程序进行格式化.因此,无可否认,图表现在更"正确",因为图表正确地推断出第9个值,但我找不到如何将标签放在相应的图表下面.

这是我的x轴代码:

 let chartView = LineChartView()
 ...
 let xAxis = chartView.xAxis
 xAxis.labelPosition = .bottom
 xAxis.labelCount = entries.count
 xAxis.drawLabelsEnabled = true
 xAxis.drawLimitLinesBehindDataEnabled = true
 xAxis.avoidFirstLastClippingEnabled = true

 // Set the x values date formatter
 let xValuesNumberFormatter = ChartXAxisFormatter()
 xValuesNumberFormatter.dateFormatter = dayNumberAndShortNameFormatter // e.g. "wed 26"
 xAxis.valueFormatter = xValuesNumberFormatter

这是我创建的ChartXAxisFormatter类:

import Foundation
import Charts

class ChartXAxisFormatter: NSObject {
    var dateFormatter: DateFormatter?
}

extension ChartXAxisFormatter: IAxisValueFormatter {

    func stringForValue(_ value: Double, axis: AxisBase?) -> String {
        if let dateFormatter = dateFormatter {

            let date = Date(timeIntervalSince1970: value)
            return dateFormatter.string(from: date)
        }

        return ""
    }

}

因此,这里的值是正确的,格式是正确的,图表的形状是正确的,但标签与相应图的对齐并不好.谢谢你的帮助

好的,我知道了!

您必须定义参考时间间隔(x轴为"0").然后计算每个x值的附加时间间隔.

ChartXAxisFormatter变为:

import Foundation
import Charts

class ChartXAxisFormatter: NSObject {
    fileprivate var dateFormatter: DateFormatter?
    fileprivate var referenceTimeInterval: TimeInterval?

    convenience init(referenceTimeInterval: TimeInterval, dateFormatter: DateFormatter) {
        self.init()
        self.referenceTimeInterval = referenceTimeInterval
        self.dateFormatter = dateFormatter
    }
}


extension ChartXAxisFormatter: IAxisValueFormatter {

    func stringForValue(_ value: Double, axis: AxisBase?) -> String {
        guard let dateFormatter = dateFormatter,
        let referenceTimeInterval = referenceTimeInterval
        else {
            return ""
        }

        let date = Date(timeIntervalSince1970: value * 3600 * 24 + referenceTimeInterval)
        return dateFormatter.string(from: date)
    }

}

然后,当我创建数据条目时,它的工作原理如下:

// (objects is defined as an array of struct with date and value)

// Define the reference time interval
var referenceTimeInterval: TimeInterval = 0
if let minTimeInterval = (objects.map { $0.date.timeIntervalSince1970 }).min() {
        referenceTimeInterval = minTimeInterval
    }


    // Define chart xValues formatter
    let formatter = DateFormatter()
    formatter.dateStyle = .short
    formatter.timeStyle = .none
    formatter.locale = Locale.current

    let xValuesNumberFormatter = ChartXAxisFormatter(referenceTimeInterval: referenceTimeInterval, dateFormatter: xValuesFormatter)



    // Define chart entries
    var entries = [ChartDataEntry]()
    for object in objects {
        let timeInterval = object.date.timeIntervalSince1970
        let xValue = (timeInterval - referenceTimeInterval) / (3600 * 24)

        let yValue = object.value
        let entry = ChartDataEntry(x: xValue, y: yValue)
        entries.append(entry)
    }

// Pass these entries and the formatter to the Chart ...

结果更好(我顺便删除了立方体):