如何为不同的 xAxis 标签呈现自定义标签颜色？答案

【问题标题】：How to render custom label colors for different xAxis labels?如何为不同的 xAxis 标签呈现自定义标签颜色？
【发布时间】：2017-06-05 05:11:07
【问题描述】：

我正在使用Charts 库创建一个图表，以便在我的应用中绘制一个组合图表。

我成功地绘制了图表。现在我想更改特定标签的xAxis 标签文本颜色。示例如图所示。

如图所示，我想更改特定值的颜色，例如 03/06 和 06/06。当我在 github 上引用该库时，他们告诉我重写 drawValues() 函数来实现这一点。由于我是快速编程的新手，我不知道如何实现这一点。请指导我如何完成这项任务。提前致谢。

【问题讨论】：

标签： ios swift ios-charts swiftcharts

【解决方案1】：

在 XAxisRenderer.swift 内部（不是 XAxisRendererHorizontalBarChart 像其他答案所建议的那样）在 drawLabels 函数上方添加这个列表和你的颜色：

 let labelTextColorList = [UIColor.black, UIColor.red, UIColor.blue, UIColor.brown, UIColor.cyan, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black, UIColor.black]

然后将 drawLabels 函数替换为以下代码：

 /// draws the x-labels on the specified y-position
open func drawLabels(context: CGContext, pos: CGFloat, anchor: CGPoint)
{
    guard
        let xAxis = self.axis as? XAxis,
        let viewPortHandler = self.viewPortHandler,
        let transformer = self.transformer
        else { return }

    #if os(OSX)
        let paraStyle = NSParagraphStyle.default().mutableCopy() as! NSMutableParagraphStyle
    #else
        let paraStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
    #endif
    paraStyle.alignment = .center

    //label attrs moved from here
    /*            let labelAttrs = [NSFontAttributeName: xAxis.labelFont,
     NSForegroundColorAttributeName: xAxis.labelTextColor,
     NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]
     */

    let labelRotationAngleRadians = xAxis.labelRotationAngle * ChartUtils.Math.FDEG2RAD

    let centeringEnabled = xAxis.isCenterAxisLabelsEnabled

    let valueToPixelMatrix = transformer.valueToPixelMatrix

    var position = CGPoint(x: 0.0, y: 0.0)

    var labelMaxSize = CGSize()

    if xAxis.isWordWrapEnabled
    {
        labelMaxSize.width = xAxis.wordWrapWidthPercent * valueToPixelMatrix.a
    }

    let entries = xAxis.entries

    for i in stride(from: 0, to: entries.count, by: 1)
    {

        //label attrs moved to here
        let labelAttrs: [String: NSObject]!

        if(i<labelTextColorList.count) {
            labelAttrs = [NSFontAttributeName: xAxis.labelFont,
                                  NSForegroundColorAttributeName: labelTextColorList[i],
                                  NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]
        }
        else {
            labelAttrs = [NSFontAttributeName: xAxis.labelFont,
                          NSForegroundColorAttributeName: xAxis.labelTextColor,
                          NSParagraphStyleAttributeName: paraStyle] as [String : NSObject]

        }
        if centeringEnabled
        {
            position.x = CGFloat(xAxis.centeredEntries[i])
        }
        else
        {
            position.x = CGFloat(entries[i])
        }

        position.y = 0.0
        position = position.applying(valueToPixelMatrix)

        if viewPortHandler.isInBoundsX(position.x)
        {
            let label = xAxis.valueFormatter?.stringForValue(xAxis.entries[i], axis: xAxis) ?? ""

            let labelns = label as NSString

            if xAxis.isAvoidFirstLastClippingEnabled
            {
                // avoid clipping of the last
                if i == xAxis.entryCount - 1 && xAxis.entryCount > 1
                {
                    let width = labelns.boundingRect(with: labelMaxSize, options: .usesLineFragmentOrigin, attributes: labelAttrs, context: nil).size.width

                    if width > viewPortHandler.offsetRight * 2.0
                        && position.x + width > viewPortHandler.chartWidth
                    {
                        position.x -= width / 2.0
                    }
                }
                else if i == 0
                { // avoid clipping of the first
                    let width = labelns.boundingRect(with: labelMaxSize, options: .usesLineFragmentOrigin, attributes: labelAttrs, context: nil).size.width
                    position.x += width / 2.0
                }
            }

            drawLabel(context: context,
                      formattedLabel: label,
                      x: position.x,
                      y: pos,
                      attributes: labelAttrs,
                      constrainedToSize: labelMaxSize,
                      anchor: anchor,
                      angleRadians: labelRotationAngleRadians)
        }
    }
}

结果：

【讨论】：

【解决方案2】：

在图表库的 XAxisRendererHorizontalBarChart.swift 文件中有以下方法。它将设置 xAxis 的文本。您可以根据自己的用例对其进行自定义。

open override func drawLabels(context: CGContext, pos: CGFloat, anchor: CGPoint)

【讨论】：

你能给我举个例子吗？