ios - 你如何以编程方式从 View Controller 中画一条线？

Question

我有一个 UIViewController。如何在其中一个以编程方式创建的 View 中画一条线？

Answer 1

有两种常见的技术。

1. 使用 CAShapeLayer :

   • 创建一个UIBezierPath (用任何你想要的替换坐标):

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

   • 创建一个CAShapeLayer使用那个 UIBezierPath :

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

   • 添加 CAShapeLayer到您的 View 层:

     [self.view.layer addSublayer:shapeLayer];
     

   在以前的 Xcode 版本中，您必须手动添加 QuartzCore.framework to your project's "Link Binary with Libraries"并导入 <QuartzCore/QuartzCore.h> .m 文件中的 header ，但这不再是必需的(如果您启用了“启用模块”和“自动链接框架”build设置)。

2. 另一种方法是子类 UIView然后使用 CoreGraphics调用 drawRect 方法:

   • 创建一个UIView子类化并定义一个 drawRect划清界限。

     您可以使用 Core Graphics 做到这一点:

     - (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];
     }
     

   • 然后您可以将此 View 类用作您的 NIB/ Storyboard或 View 的基类，或者您可以让您的 View Controller 以编程方式将其添加为 subview :

     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:

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)
   

2. UIView子类:

   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()
       }
   
   }
   

   并将其添加到您的 View 层次结构中:

   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
   

   在上面，我要添加 PathView以编程方式，但您也可以通过 IB 添加它，只需设置它的 path以编程方式。