UIView set only side borders

问题:

Is there a way to set the sides of the border of a UIView to one color and leave the top and the bottom another?

回答1:

Nope—CALayer borders don’t support that behavior. The easiest way to accomplish what you want is adding an n-point-wide opaque subview with your desired border color as its background color on each side of your view.

Example:

CGSize mainViewSize = theView.bounds.size;
CGFloat borderWidth = 2;
UIColor *borderColor = [UIColor redColor];
UIView *leftView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, borderWidth, mainViewSize.height)];
UIView *rightView = [[UIView alloc] initWithFrame:CGRectMake(mainViewSize.width - borderWidth, 0, borderWidth, mainViewSize.height)];
leftView.opaque = YES;
rightView.opaque = YES;
leftView.backgroundColor = borderColor;
rightView.backgroundColor = borderColor;

// for bonus points, set the views' autoresizing mask so they'll stay with the edges:
leftView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleRightMargin;
rightView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleLeftMargin;

[theView addSubview:leftView];
[theView addSubview:rightView];

[leftView release];
[rightView release];

Note that this won’t quite match the behavior of CALayer borders—the left and right border views will always be inside the boundaries of their superview.

回答2:

The answer with the views that works like borders are very nice, but remember that every view is a UI Object that cost lots of memory.

I whould use uivew's layer to paint a stroke with color on an already existing UIview.

-(CAShapeLayer*)drawLineFromPoint:(CGPoint)fromPoint toPoint:(CGPoint) toPoint withColor:(UIColor *)color andLineWidth:(CGFloat)lineWidth{

CAShapeLayer *lineShape = nil;
CGMutablePathRef linePath = nil;

linePath = CGPathCreateMutable();
lineShape = [CAShapeLayer layer];

lineShape.lineWidth = lineWidth;
lineShape.strokeColor = color.CGColor;

NSUInteger x = fromPoint.x;
NSUInteger y = fromPoint.y;

NSUInteger toX = toPoint.x;
NSUInteger toY = toPoint.y;

CGPathMoveToPoint(linePath, nil, x, y);
CGPathAddLineToPoint(linePath, nil, toX, toY);

lineShape.path = linePath;
CGPathRelease(linePath);
return lineShape;}

and add it to our view.

CAShapeLayer* borderLine=[self drawLineFromPoint:CGPointMake(0, 0) toPoint:CGPointMake(0,_myView.frame.size.height) withColor:[UIColor lightGrayColor] andLineWidth:1.0f];

[_myView.layer addSublayer:borderLine];

So... We take a point and actually painting a line from top to the bottom of our view. The result is that there is a line that looks like a one pixel width border.

回答3:

Updated for Swift 3.0

I wrote a Swift extension (for a UIButton) that simulates setting a border on any side of a UIView to a given color and width. It's similar to @Noah Witherspoon's approach, but self-contained and autolayout constraint based.

 // Swift 3.0
extension UIView {

  enum Border {
    case left
    case right
    case top
    case bottom
  }

  func setBorder(border: UIView.Border, weight: CGFloat, color: UIColor ) {

    let lineView = UIView()
    addSubview(lineView)
    lineView.backgroundColor = color
    lineView.translatesAutoresizingMaskIntoConstraints = false

    switch border {

    case .left:
      lineView.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
      lineView.topAnchor.constraint(equalTo: topAnchor).isActive = true
      lineView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
      lineView.widthAnchor.constraint(equalToConstant: weight).isActive = true

    case .right:
      lineView.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
      lineView.topAnchor.constraint(equalTo: topAnchor).isActive = true
      lineView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
      lineView.widthAnchor.constraint(equalToConstant: weight).isActive = true

    case .top:
      lineView.topAnchor.constraint(equalTo: topAnchor).isActive = true
      lineView.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
      lineView.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
      lineView.heightAnchor.constraint(equalToConstant: weight).isActive = true

    case .bottom:
      lineView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
      lineView.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
      lineView.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
      lineView.heightAnchor.constraint(equalToConstant: weight).isActive = true
    }
  }
}    

回答4:

This sounds like one of two answers:

If your view is a static size, then just put a UIView behind it that is 2 pixels wider and 2 pixels shorter than your front view.

If it is non-static sized then you could do the same, resizing the backing view whenever your foreground view is resized, or implement a custom object that implements a UIView, and implement (override) your own drawRect routine.

回答5:

NAUIViewWithBorders did the trick for me. See also the creator's SO post here. Worth checking out if you need this functionality for more than a couple views.

回答6:

public extension UIView {
// Border type and arbitrary tag values to identify UIView borders as subviews
public enum BorderType: Int {
    case left = 20000
    case right = 20001
    case top = 20002
    case bottom = 20003
}

public func addBorder(borderType: BorderType, width: CGFloat, color: UIColor) {
    // figure out frame and resizing based on border type
    var autoresizingMask: UIViewAutoresizing
    var layerFrame: CGRect
    switch borderType {
    case .left:
        layerFrame = CGRect(x: 0, y: 0, width: width, height: self.bounds.height)
        autoresizingMask = [ .flexibleHeight, .flexibleRightMargin ]
    case .right:
        layerFrame = CGRect(x: self.bounds.width - width, y: 0, width: width, height: self.bounds.height)
        autoresizingMask = [ .flexibleHeight, .flexibleLeftMargin ]
    case .top:
        layerFrame = CGRect(x: 0, y: 0, width: self.bounds.width, height: width)
        autoresizingMask = [ .flexibleWidth, .flexibleBottomMargin ]
    case .bottom:
        layerFrame = CGRect(x: 0, y: self.bounds.height - width, width: self.bounds.width, height: width)
        autoresizingMask = [ .flexibleWidth, .flexibleTopMargin ]
    }

    // look for the existing border in subviews
    var newView: UIView?
    for eachSubview in self.subviews {
        if eachSubview.tag == borderType.rawValue {
            newView = eachSubview
            break
        }
    }

    // set properties on existing view, or create a new one
    if newView == nil {
        newView = UIView(frame: layerFrame)
        newView?.tag = borderType.rawValue
        self.addSubview(newView!)
    } else {
        newView?.frame = layerFrame
    }
    newView?.backgroundColor = color
    newView?.autoresizingMask = autoresizingMask
}