CALayer IOS上的自动布局约束

Question

嗨,我正在开发iPhone应用程序,我试图为edittext设置一个边框.我是按照以下方式做到的:

 int borderWidth = 1;
CALayer *leftBorder = [CALayer layer];

leftBorder.borderColor = [UIColor whiteColor].CGColor;
leftBorder.borderWidth = borderWidth;

leftBorder.frame = CGRectMake(0, textField.frame.size.height - borderWidth, textField
                              .frame.size.width, borderWidth);
[textField.layer addSublayer:leftBorder];

我对IB中的edittext设置了一些约束,这样当我旋转设备时,它会根据它调整文本字段的宽度.我的问题是调整edittext的宽度而不是调整我为编辑文本设置的CALayer的宽度.所以我想我必须为我的CALayer项目设置一些约束.但我不知道该怎么做.有人知道吗？需要帮忙.谢谢.

Answer 1

整个自动化业务是特定于视图的.图层不会自动调整大小.

您需要做的 - 在代码中 - 是自己调整图层大小

例如

在viewController中你会做

- (void) viewDidLayoutSubviews {
  [super viewDidLayoutSubviews]; //if you want superclass's behaviour... 
  // resize your layers based on the view's new frame
  self.editViewBorderLayer.frame = self.editView.bounds;
}

或者在你可以使用的自定义UIView中

- (void)layoutSubviews {
  [super layoutSubviews]; //if you want superclass's behaviour...  (and lay outing of children)
  // resize your layers based on the view's new frame
  layer.frame = self.bounds;
}

Answer 2

检查此解决方案.使用KVO,路径为"YourView.bounds",如下所示.

self.addObserver(self, forKeyPath: "YourView.bounds", options: .New, context: nil)

然后按照下面的说明处理它.

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
        if (keyPath == "YourView.bounds") {
            YourLayer.frame = YourView.bounds
            return
        }
        super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
    }

有关详细信息,请参阅以下链接.

https://theswiftdev.com/2015/03/28/auto-layout-with-layers/

Answer 3

根据这个答案，layoutSubviews在所有需要的情况下都不会被调用。我发现这个委托方法更有效：

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if(self != nil) {
        [self.layer addSublayer:self.mySublayer];
    }
    return self;
}

- (void)layoutSublayersOfLayer:(CALayer*)layer
{
    self.mySublayer.frame = self.bounds;
}

Answer 4

我实现了自定义视图的layoutSubviews方法。在此方法中，我只是更新每个子图层的框架以匹配子视图图层的当前边界。

-(void)layoutSubviews{
      sublayer1.frame = self.layer.bounds;
}

Answer 5

我用虚线边框创建时的解决方案

class DashedBorderView: UIView {

   let dashedBorder = CAShapeLayer()

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

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

   private func commonInit() {
       //custom initialization
       dashedBorder.strokeColor = UIColor.red.cgColor
       dashedBorder.lineDashPattern = [2, 2]
       dashedBorder.frame = self.bounds
       dashedBorder.fillColor = nil
       dashedBorder.cornerRadius = 2
       dashedBorder.path = UIBezierPath(rect: self.bounds).cgPath
       self.layer.addSublayer(dashedBorder)
   }

   override func layoutSublayers(of layer: CALayer) {
       super.layoutSublayers(of: layer)
       dashedBorder.path = UIBezierPath(rect: self.bounds).cgPath
       dashedBorder.frame = self.bounds
   }
}