如何在饼图上为标签找到合适的位置?

我没有使用任何库,因此这不是切片外部饼图条目具有不同位置偏移“>this

var部分:【piechartSection】=[]{
DIDSET {
设置需要显示()
}
}

覆盖func draw(rect:cgrect){
设sumofsections=sections.map$0.value.reduce(0,+)
var路径开始=cgfloat.pi
让smallerDimension=min(高度、宽度)
对于分区中的分区{
/绘图部分
设百分比=截面值/截面总和
让pathend=pathstart+cgfloat.pi*百分比.f*2
让path=uibezierpath(arcenter:cgpoint(x:bounds.midx,y:bounds.midy)),
半径:小尺寸/4,开始角度:路径开始,结束角度:路径结束,顺时针:真)

/绘制标签
//这是我计算标签位置的尝试
让中间角度=(路径开始+路径结束)/2
让textx=bounds.midx+smallerdimension*3/8*cos(中间角)
让texty=bounds.midy+smallerDimension*3/8*sin(middangle)

//创建要显示的文本,这不相关吗?
让attributedString=nsmutablettributedString(string:section.name,attributes:)[
.背景色:uicolor.black.withalphacomponent(0.15),
.FONT:uiFONT.systemFONT(OFSIZE:9)
)
让格式化程序=数字格式化程序()。
formatter.maximumFractionDigits=0
让percentageString=“\n”+formatter.string(从:(percentage*100)作为nsnumber)!+“%”
attributedString.append(nsattributedString(string:percentageString,attributes:)[
.背景色:uicolor.black.withalphacomponent(0.5),
.FONT:uiFONT.systemFONT(OFSIZE:12)
))
attributedString.draw(在:cgpoint(x:textx,y:texty))。

/笔划路径
path.linewidth=6
节.color.setstroke())
路径选择()
pathStart=路径结束
}
}
< /代码> 

并且apiechartsectionis a simple struct:。


struct piechartsection{
Let值:Double
让颜色:uicolor
let name:字符串
}
< /代码> 

馅饼看起来不错,但标签有时离馅饼很远,有时离它很近:



我认为问题在于,nsattriutedstring.drawalways draws the text from the to p left corner,means that theto p left cornersof the text are all equal distance to the pie,which I need to draw the text so that theirclosest points to the pie.are all equal distance to the pie.


我怎样才能画出那样的文字?


我没有使用可可荚,因为我发现很难按照我想要的方式使用高级API制作图表。只是太复杂了。我希望对饼图的绘制方式进行较低级别的控制。.

我自己画的馅饼区是这样的:

var sections: [PieChartSection] = [] {
    didSet {
        setNeedsDisplay()
    }
}

override func draw(_ rect: CGRect) {
    let sumOfSections = sections.map { $0.value }.reduce(0, +)
    var pathStart = CGFloat.pi
    let smallerDimension = min(height, width)
    for section in sections {
        // draw section
        let percentage = section.value / sumOfSections
        let pathEnd = pathStart + CGFloat.pi * percentage.f * 2
        let path = UIBezierPath(arcCenter: CGPoint(x: bounds.midX, y: bounds.midY),
                                radius: smallerDimension / 4, startAngle: pathStart, endAngle: pathEnd, clockwise: true)

        //draw labels
        // this is my attempt at calculating the position of the labels
        let midAngle = (pathStart + pathEnd) / 2
        let textX = bounds.midX + smallerDimension * 3 / 8 * cos(midAngle)
        let textY = bounds.midY + smallerDimension * 3 / 8 * sin(midAngle)

        // creating the text to be shown, don't this is relevant
        let attributedString = NSMutableAttributedString(string: section.name, attributes: [
            .foregroundColor: UIColor.black.withAlphaComponent(0.15),
            .font: UIFont.systemFont(ofSize: 9)
            ])
        let formatter = NumberFormatter()
        formatter.maximumFractionDigits = 0
        let percentageString = "\n" + formatter.string(from: (percentage * 100) as NSNumber)! + "%"
        attributedString.append(NSAttributedString(string: percentageString, attributes: [
            .foregroundColor: UIColor.black.withAlphaComponent(0.5),
            .font: UIFont.systemFont(ofSize: 12)
            ]))
        attributedString.draw(at: CGPoint(x: textX, y: textY))

        // stroke path
        path.lineWidth = 6
        section.color.setStroke()
        path.stroke()
        pathStart = pathEnd
    }
}


和APieChartSection是一个简单结构:

struct PieChartSection {
    let value: Double
    let color: UIColor
    let name: String
}


馅饼看起来不错,但标签有时离馅饼很远,有时离它很近:



我想问题是NSAttriutedString.draw总是从左上角绘制文本,这意味着左上角文本与饼图的距离相等,而我需要绘制文本,以便最接近饼图的点与饼的距离相等。

我怎样才能画出那样的文字?

我没有使用可可荚,因为我发现很难按照我想要的方式使用高级API制作图表。只是太复杂了。我想对我的饼图的绘制方式进行较低级别的控制。