有两种常用的技巧.

1. 使用 CAShapeLayer:

• 创建一个UIBezierPath(用你想要的替换坐标):

• Create a UIBezierPath (replace the coordinates with whatever you want):

UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(10.0, 10.0)];
[path addLineToPoint:CGPointMake(100.0, 100.0)];

CAShapeLayer *shapeLayer = [CAShapeLayer layer];
shapeLayer.path = [path CGPath];
shapeLayer.strokeColor = [[UIColor blueColor] CGColor];
shapeLayer.lineWidth = 3.0;
shapeLayer.fillColor = [[UIColor clearColor] CGColor];

[self.view.layer addSublayer:shapeLayer];

在以前版本的 Xcode 中，您必须手动将 QuartzCore.framework 添加到您的项目的Link Binary with Libraries" 并在您的 .m 文件中导入 <QuartzCore/QuartzCore.h> 标头，但这不再是必需的(如果您有Enable Modules"和自动链接框架"构建设置打开).

In previous versions of Xcode, you had to manually add QuartzCore.framework to your project's "Link Binary with Libraries" and import the <QuartzCore/QuartzCore.h> header in your .m file, but that's not necessary anymore (if you have the "Enable Modules" and "Link Frameworks Automatically" build settings turned on).

另一种方法是继承 UIView 然后使用 CoreGraphics 在 drawRect 方法中调用:

The other approach is to subclass UIView and then use CoreGraphics calls in the drawRect method:

• 创建一个 UIView 子类并定义一个绘制线条的 drawRect.

• Create a UIView subclass and define a drawRect that draws your line.

您可以使用 Core Graphics 做到这一点:

You can do this with Core Graphics:

- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetStrokeColorWithColor(context, [[UIColor blueColor] CGColor]);
    CGContextSetLineWidth(context, 3.0);
    CGContextMoveToPoint(context, 10.0, 10.0);
    CGContextAddLineToPoint(context, 100.0, 100.0);
    CGContextDrawPath(context, kCGPathStroke);
}

或者使用UIKit:

- (void)drawRect:(CGRect)rect {
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(10.0, 10.0)];
    [path addLineToPoint:CGPointMake(100.0, 100.0)];
    path.lineWidth = 3;
    [[UIColor blueColor] setStroke];
    [path stroke];
}

PathView *pathView = [[PathView alloc] initWithFrame:self.view.bounds];
pathView.backgroundColor = [UIColor clearColor];

[self.view addSubview: pathView];

上述两种方法的 Swift 版本如下:

The Swift renditions of the two above approaches are as follows:

1. CAShapeLayer:

// create path

let path = UIBezierPath()
path.move(to: CGPoint(x: 10, y: 10))
path.addLine(to: CGPoint(x: 100, y: 100))

// Create a `CAShapeLayer` that uses that `UIBezierPath`:

let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.strokeColor = UIColor.blue.cgColor
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.lineWidth = 3

// Add that `CAShapeLayer` to your view's layer:

view.layer.addSublayer(shapeLayer)

class PathView: UIView {

    var path: UIBezierPath?           { didSet { setNeedsDisplay() } }
    var pathColor: UIColor = .blue    { didSet { setNeedsDisplay() } }

    override func draw(_ rect: CGRect) {
        // stroke the path

        pathColor.setStroke()
        path?.stroke()
    }

}

let pathView = PathView()
pathView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(pathView)

NSLayoutConstraint.activate([
    pathView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
    pathView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
    pathView.topAnchor.constraint(equalTo: view.topAnchor),
    pathView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
])

pathView.backgroundColor = .clear

let path = UIBezierPath()
path.move(to: CGPoint(x: 10, y: 10))
path.addLine(to: CGPoint(x: 100, y: 100))
path.lineWidth = 3

pathView.path = path