在 UIView 外部添加边框(而不是在内部)

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Increase the width and height of view's frame with border width before adding the border:

float borderWidth = 2.0f
CGRect frame = self.frame;
frame.width += borderWidth;
frame.height += borderWidth;
self.layer.borderColor = [UIColor yellowColor].CGColor;
self.layer.borderWidth = 2.0f;

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最佳答案

Unfortunately, there isn't simply a little property you can set to align the border to the outside. It draws aligned to the inside because the UIViews default drawing operations draw within its bounds.

The simplest solution that comes to mind would be to expand the UIView by the size of the border width when applying the border:

CGFloat borderWidth = 2.0f;


self.frame = CGRectInset(self.frame, -borderWidth, -borderWidth);
self.layer.borderColor = [UIColor yellowColor].CGColor;
self.layer.borderWidth = borderWidth;

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Well there is no direct method to do it You can consider some workarounds.

Change and increase the frame and add bordercolor as you did
Add a view behind the current view with the larger size so that it appears as border.Can be worked as a custom class of view

If you dont need a definite border (clearcut border) then you can depend on shadow for the purpose

[view1 setBackgroundColor:[UIColor blackColor]];
UIColor *color = [UIColor yellowColor];
view1.layer.shadowColor = [color CGColor];
view1.layer.shadowRadius = 10.0f;
view1.layer.shadowOpacity = 1;
view1.layer.shadowOffset = CGSizeZero;
view1.layer.masksToBounds = NO;

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Ok, there already is an accepted answer but I think there is a better way to do it, you just have to had a new layer a bit larger than your view and do not mask it to the bounds of the view's layer (which actually is the default behaviour). Here is the sample code :

CALayer * externalBorder = [CALayer layer];
externalBorder.frame = CGRectMake(-1, -1, myView.frame.size.width+2, myView.frame.size.height+2);
externalBorder.borderColor = [UIColor blackColor].CGColor;
externalBorder.borderWidth = 1.0;


[myView.layer addSublayer:externalBorder];
myView.layer.masksToBounds = NO;

Of course this is if you want your border to be 1 unity large, if you want more you adapt the borderWidth and the frame of the layer accordingly. This is better than using a second view a bit larger as a CALayer is lighter than a UIView and you don't have do modify the frame of myView, which is good for instance if myView is aUIImageView

N.B : For me the result was not perfect on simulator (the layer was not exactly at the right position so the layer was thicker on one side sometimes) but was exactly what is asked for on real device.

EDIT

Actually the problem I talk about in the N.B was just because I had reduced the screen of the simulator, on normal size there is absolutely no issue

Hope it helps

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For a Swift implementation, you can add this as a UIView extension.

extension UIView {


struct Constants {
static let ExternalBorderName = "externalBorder"
}


func addExternalBorder(borderWidth: CGFloat = 2.0, borderColor: UIColor = UIColor.whiteColor()) -> CALayer {
let externalBorder = CALayer()
externalBorder.frame = CGRectMake(-borderWidth, -borderWidth, frame.size.width + 2 * borderWidth, frame.size.height + 2 * borderWidth)
externalBorder.borderColor = borderColor.CGColor
externalBorder.borderWidth = borderWidth
externalBorder.name = Constants.ExternalBorderName


layer.insertSublayer(externalBorder, atIndex: 0)
layer.masksToBounds = false


return externalBorder
}


func removeExternalBorders() {
layer.sublayers?.filter() { $0.name == Constants.ExternalBorderName }.forEach() {
$0.removeFromSuperlayer()
}
}


func removeExternalBorder(externalBorder: CALayer) {
guard externalBorder.name == Constants.ExternalBorderName else { return }
externalBorder.removeFromSuperlayer()
}


}

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With the above accepted best answer i made experiences with such not nice results and unsightly edges:

So i will share my UIView Swift extension with you, that uses a UIBezierPath instead as border outline – without unsightly edges (inspired by @Fattie):

//  UIView+BezierPathBorder.swift


import UIKit


extension UIView {


fileprivate var bezierPathIdentifier:String { return "bezierPathBorderLayer" }


fileprivate var bezierPathBorder:CAShapeLayer? {
return (self.layer.sublayers?.filter({ (layer) -> Bool in
return layer.name == self.bezierPathIdentifier && (layer as? CAShapeLayer) != nil
}) as? [CAShapeLayer])?.first
}


func bezierPathBorder(_ color:UIColor = .white, width:CGFloat = 1) {


var border = self.bezierPathBorder
let path = UIBezierPath(roundedRect: self.bounds, cornerRadius:self.layer.cornerRadius)
let mask = CAShapeLayer()
mask.path = path.cgPath
self.layer.mask = mask


if (border == nil) {
border = CAShapeLayer()
border!.name = self.bezierPathIdentifier
self.layer.addSublayer(border!)
}


border!.frame = self.bounds
let pathUsingCorrectInsetIfAny =
UIBezierPath(roundedRect: border!.bounds, cornerRadius:self.layer.cornerRadius)


border!.path = pathUsingCorrectInsetIfAny.cgPath
border!.fillColor = UIColor.clear.cgColor
border!.strokeColor = color.cgColor
border!.lineWidth = width * 2
}


func removeBezierPathBorder() {
self.layer.mask = nil
self.bezierPathBorder?.removeFromSuperlayer()
}


}

Example:

let view = UIView(frame: CGRect(x: 20, y: 20, width: 100, height: 100))
view.layer.cornerRadius = view.frame.width / 2
view.backgroundColor = .red


//add white 2 pixel border outline
view.bezierPathBorder(.white, width: 2)


//remove border outline (optional)
view.removeBezierPathBorder()

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I liked solution of @picciano If you want exploding circle instead of square replace addExternalBorder function with:

func addExternalBorder(borderWidth: CGFloat = 2.0, borderColor: UIColor = UIColor.white) {
let externalBorder = CALayer()
externalBorder.frame = CGRect(x: -borderWidth, y: -borderWidth, width: frame.size.width + 2 * borderWidth, height: frame.size.height + 2 * borderWidth)
externalBorder.borderColor = borderColor.cgColor
externalBorder.borderWidth = borderWidth
externalBorder.cornerRadius = (frame.size.width + 2 * borderWidth) / 2
externalBorder.name = Constants.ExternalBorderName
layer.insertSublayer(externalBorder, at: 0)
layer.masksToBounds = false


}

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I liked solution of @picciano & @Maksim Kniazev. We can also create annular border with following:

func addExternalAnnularBorder(borderWidth: CGFloat = 2.0, borderColor: UIColor = UIColor.white) {
let externalBorder = CALayer()
externalBorder.frame = CGRect(x: -borderWidth*2, y: -borderWidth*2, width: frame.size.width + 4 * borderWidth, height: frame.size.height + 4 * borderWidth)
externalBorder.borderColor = borderColor.cgColor
externalBorder.borderWidth = borderWidth
externalBorder.cornerRadius = (frame.size.width + 4 * borderWidth) / 2
externalBorder.name = Constants.ExternalBorderName
layer.insertSublayer(externalBorder, at: 0)
layer.masksToBounds = false
}

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There is actually a very simple solution. Just set them both like this:

view.layer.borderWidth = 5


view.layer.borderColor = UIColor(red: 1, green: 1, blue: 1, alpha: 0.5).cgColor


view.backgroundColor = UIColor(red: 1, green: 1, blue: 1, alpha: 0.25).cgColor

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How I placed a border around my UI view (main - SubscriptionAd) in Storyboard is to place it inside another UI view (background - BackgroundAd). The Background UIView has a background colour that matches the border colour i want, and the Main UIView has constraints value 2 from each side.

I will link the background view to my ViewController and then turn the border on and off by changing the background colour.

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Swift 5

extension UIView {
fileprivate struct Constants {
static let externalBorderName = "externalBorder"
}


func addExternalBorder(borderWidth: CGFloat = 2.0, borderColor: UIColor = UIColor.white) -> CALayer {
let externalBorder = CALayer()
externalBorder.frame = CGRect(x: -borderWidth, y: -borderWidth, width: frame.size.width + 2 * borderWidth, height: frame.size.height + 2 * borderWidth)
externalBorder.borderColor = borderColor.cgColor
externalBorder.borderWidth = borderWidth
externalBorder.name = Constants.ExternalBorderName


layer.insertSublayer(externalBorder, at: 0)
layer.masksToBounds = false


return externalBorder
}


func removeExternalBorders() {
layer.sublayers?.filter() { $0.name == Constants.externalBorderName }.forEach() {
$0.removeFromSuperlayer()
}
}


func removeExternalBorder(externalBorder: CALayer) {
guard externalBorder.name == Constants.externalBorderName else { return }
externalBorder.removeFromSuperlayer()
}
}