從圓形畫出圓形和線段

Question

我想畫一個圓形並從這個圓形畫出線段。抱歉，因爲我發現了很多關於stackoverflow的主題，但仍然沒有人能夠幫助我完全理解。你能給我一個這樣的示例代碼嗎？我想要像下面的圖片的結果。非常感謝

Answer 1

打開一個新的Swift 3遊樂場並將下面的代碼粘貼到它。您應該在右側看到一個「w 512 h 512」註釋，點擊它並出現一個眼睛。你應該在那一刻看到一些繪圖。

//: Playground - noun: a place where people can play 
import UIKit 
import CoreGraphics 

public func makePieChart()-> UIImage? 
{ 
    let size = CGSize(width: 512, height:512) 
    let centerX = size.width/2.0 
    let centerY = size.height/2.0 
    let center = CGPoint(x: centerX, y: centerY) 
    let chartRadius = size.width/2.0 

    UIGraphicsBeginImageContextWithOptions(size, false, 0.0) 
    defer 
    { 
     UIGraphicsEndImageContext() 
    } 


    guard let quartz = UIGraphicsGetCurrentContext() else 
    { 
     return nil 
    } 
    let π = CGFloat.pi 

    quartz.move(to: center) 
    quartz.addArc(center: center, radius: chartRadius, startAngle: 0.0, endAngle: π/3.0, clockwise: false) 
    quartz.closePath() // path will complete back at the last move to (center of the circle) 

    quartz.setFillColor(UIColor.red.cgColor) 
    quartz.fillPath() 


    quartz.move(to: center) 
    quartz.addArc(center: center, radius: chartRadius, startAngle: π/3.0, endAngle: π, clockwise: false) 

    quartz.closePath() // path will complete back at the last move to (center of the circle) 

    quartz.setFillColor(UIColor.yellow.cgColor) 
    quartz.fillPath() 
    quartz.move(to: center) 
    quartz.addArc(center: center, radius: chartRadius, startAngle: π, endAngle: 0.0, clockwise: false) 

    quartz.closePath() // path will complete back at the last move to (center of the circle) 

    quartz.setFillColor(UIColor.blue.cgColor) 
    quartz.fillPath() 
    return UIGraphicsGetImageFromCurrentImageContext() 
} 

let image = makePieChart()