Swift 3：绘制一个矩形

Question

我是 Swift 的 3 天新手，我正在尝试弄清楚如何绘制一个矩形。我对这门语言太陌生了，不知道要扩展的类和要覆盖的方法，我四处寻找示例代码，但似乎没有任何效果（我将其归因于我对 swift 3 的使用）。

我现在正在尝试的是：

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()


        let k = Draw(frame: CGRect(
            origin: CGPoint(x: 50, y: 50),
            size: CGSize(width: 100, height: 100)))

        k.draw(CGRect(
            origin: CGPoint(x: 50, y: 50),
            size: CGSize(width: 100, height: 100)));
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}
class Draw: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func draw(_ rect: CGRect) {
        let h = rect.height
        let w = rect.width
        var color:UIColor = UIColor.yellow()

        var drect = CGRect(x: (w * 0.25),y: (h * 0.25),width: (w * 0.5),height: (h * 0.5))
        var bpath:UIBezierPath = UIBezierPath(rect: drect)

        color.set()
        bpath.stroke()

        print("it ran")

        NSLog("drawRect has updated the view")

    }

}

这并没有做任何事情。帮助。

Answer 1

为了查看视图，您需要创建一个视图并为其设置框架，以便它知道要制作多大。

如果您将代码放在 Playground 中，然后添加此行：

let d = Draw(frame: CGRect(x: 0, y: 0, width: 100, height: 100))

您将能够单击右侧的快速查看，然后您将看到该视图。

---

您还可以在ViewController 中将视图添加为view 的子视图，然后您将在iPhone 上看到它：

override func viewDidLoad() {
    super.viewDidLoad()

    let k = Draw(frame: CGRect(
        origin: CGPoint(x: 50, y: 50),
        size: CGSize(width: 100, height: 100)))

    // Add the view to the view hierarchy so that it shows up on screen
    self.view.addSubview(k)
}

请注意，您从不直接致电draw(_:)。 Cocoa Touch 调用它来显示视图。

Answer 2

创建一个类，我把它放在一个单独的 Swift 3 文件中。

//
//  Plot_Demo.swift
//
//  Storyboard is not good in creating self adapting UI
//  Plot_Demo creates the drawing programatically.

import Foundation
import UIKit

public class Plot_Demo: UIView
{
    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    public override func draw(_ frame: CGRect) {
        let h = frame.height
        let w = frame.width
        let color:UIColor = UIColor.yellow

        let drect = CGRect(x: (w * 0.25), y: (h * 0.25), width: (w * 0.5), height: (h * 0.5))
        let bpath:UIBezierPath = UIBezierPath(rect: drect)

        color.set()
        bpath.stroke()

        print("it ran")
        NSLog("drawRect has updated the view")
    }
}

UIViewController 对象中的使用示例：

override func viewDidLoad() {
    super.viewDidLoad()

    // Instantiate a new Plot_Demo object (inherits and has all properties of UIView)
    let k = Plot_Demo(frame: CGRect(x: 75, y: 75, width: 150, height: 150))

    // Put the rectangle in the canvas in this new object
    k.draw(CGRect(x: 50, y: 50, width: 100, height: 100))

    // view: UIView was created earlier using StoryBoard
    // Display the contents (our rectangle) by attaching it
    self.view.addSubview(k)
}

在 iPhone 模拟器和 iPhone 上运行：

使用 XCode 版本 8.0 (8A218a)，Swift 3，目标 iOS 10.0

Answer 3

这是绘制矩形的另一种方式，

第 1 步：获取给定点的矩形路径

（注意：arrPathPoints 必须为 4 才能绘制矩形），

func getPathPayer(arrPathPoints:[CGPoint]) throws -> CAShapeLayer {
        enum PathError : Error{
            case moreThan2PointsNeeded
        }

        guard arrPathPoints.count > 2 else {
            throw PathError.moreThan2PointsNeeded
        }

        let lineColor = UIColor.blue
        let lineWidth: CGFloat = 2
        let path = UIBezierPath()
        let pathLayer = CAShapeLayer()

        for (index,pathPoint) in arrPathPoints.enumerated() {
            switch index {
            //First point
            case 0:
                path.move(to: pathPoint)

            //Last point
            case arrPathPoints.count - 1:
                path.addLine(to: pathPoint)
                path.close()

            //Middle Points
            default:
                path.addLine(to: pathPoint)
            }
        }

        pathLayer.path = path.cgPath
        pathLayer.strokeColor = lineColor.cgColor
        pathLayer.lineWidth = lineWidth
        pathLayer.fillColor = UIColor.clear.cgColor

        return pathLayer
    }

第2步：用法，这样的调用方法，

override func viewDidLoad() {
        super.viewDidLoad()

        do {
            let rectangleLayer = try getPathPayer(arrPathPoints: [
                CGPoint(x: 110, y: 110),    //Top-Left
                CGPoint(x: 130, y: 110),    //Top-Right
                CGPoint(x: 130, y: 130),    //Bottom-Right
                CGPoint(x: 110, y: 130)])   //Bottom-Left
            view.layer.addSublayer(rectangleLayer)
        } catch {
            debugPrint(error)
        }
    }

Answer 4

关于如何使用 Swift 5 绘制矩形的我的版本。

首先创建一个类来进行绘图。它使用 CoreGraphics 进行绘图，而不是 UIKit。

import UIKit

class DrawRectangle: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func draw(_ rect: CGRect) {

        guard let context = UIGraphicsGetCurrentContext() else {
            print("could not get graphics context")
            return
        }

        context.setStrokeColor(UIColor.yellow.cgColor)
        context.setLineWidth(2)
        context.stroke(rect.insetBy(dx: 10, dy: 10))
    }
}

然后把它放到你的 ViewController 的viewDidLoad()

    let myView = DrawRectangle(frame: CGRect(x: 50, y: 50, width: 100, height: 100))

    self.view.addSubview(myView)