UIView 只设置侧边框

Question

有没有办法将 UIView 的边框设置为一种颜色，而顶部和底部另一种颜色？

Answer 1

不——CALayer 边框不支持这种行为。完成您想要的最简单的方法是在视图的每一侧添加一个 n 点宽的不透明子视图，并使用所需的边框颜色作为其背景颜色。

例子：

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];

请注意，这与 CALayer 边框的行为不太匹配——左右边框视图将始终位于其父视图的边界内。

Answer 2

类似于边框的视图的答案非常好，但请记住，每个视图都是一个消耗大量内存的 UI 对象。

我应该使用 uivew 的图层在已经存在的 UIview 上绘制带有颜色的笔触。

-(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;}

并将其添加到我们的视图中。

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

[_myView.layer addSublayer:borderLine];

所以...我们取一个点，实际上从视图的顶部到底部绘制一条线。结果是有一条线看起来像一个像素宽度的边框。

Answer 3

为 Swift 3.0 更新

我编写了一个 Swift 扩展（用于 UIButton），它模拟将 UIView 任意一侧的边框设置为给定的颜色和宽度。它类似于@Noah Witherspoon 的方法，但基于自包含和自动布局约束。

 // 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
    }
  }
}    

Answer 4

这听起来像是两个答案之一：

如果您的视图是静态尺寸，那么只需在其后面放置一个比前视图宽 2 像素、短 2 像素的 UIView。

如果它是非静态大小的，那么您也可以这样做，在调整前景视图大小时调整后备视图的大小，或者实现一个实现 UIView 的自定义对象，并实现（覆盖）您自己的 drawRect 例程。

Answer 5

NAUIViewWithBorders 帮了我大忙。另请参阅创建者的SO post here。如果您需要此功能以获得多个视图，则值得一试。

Answer 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
}