What I have:
To create this line, I basically have an UIView and I do the following:
void setLayerToLineFromAToB(CALayer *layer, CGPoint a, CGPoint b, CGFloat lineWidth)
{
CGPoint center = { 0.5 * (a.x + b.x), 0.5 * (a.y + b.y) };
CGFloat length = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
CGFloat angle = atan2(a.y - b.y, a.x - b.x);
layer.position = center;
layer.bounds = (CGRect) { {0, 0}, { length + lineWidth, lineWidth } };
layer.transform = CATransform3DMakeRotation(angle, 0, 0, 1);
}
Note: This code was found here on stackoverflow, so if someone can give me the reference to it I would appreciate.
What I want:
Ok so the "only" thing I need is to create this pattern on the UIView. I know I am able to do this using Quartz2D (a simple way to do it can be found here). But I want to do it by manipulating the CALayer and not going to to the draw method. Why? Because of the transformation I am making on my UIView, I am not able to draw correctly using the draw method.
Edit 1:
Just to illustrate my problem:
Normally what you have is UIView and then you basically just draw something in it (in this case a simple line). The solution I found to get rid of the "gray" area, was to instead of drawing something, just transform the UIView itself. It work well, if you want a fully filled line, the problem comes when you want a dashed one.
Check UIBezierPath setLineDash:count:phase: method:
- (void)setLineDash:(const CGFloat *)pattern count:(NSInteger)count phase:(CGFloat)phase` method.
This allows you to draw dashed lines.
- First add a
CAShapeLayer. Add it as sublayer to yourUIView. It has apathproperty. - Now make an object of
UIBezierPath. Draw the line usingsetLineDash.
For example:
UIBezierPath *path = [UIBezierPath bezierPath];
//draw a line
[path moveToPoint:yourStartPoint]; //add yourStartPoint here
[path addLineToPoint:yourEndPoint];// add yourEndPoint here
[path stroke];
CGFloat dashPattern[] = {2.0f,6.0f,4.0f,2.0f}; //make your pattern here
[path setLineDash:dashPattern count:4 phase:3];
UIColor *fill = [UIColor blueColor];
shapelayer.strokeStart = 0.0;
shapelayer.strokeColor = fill.CGColor;
shapelayer.lineWidth = 5.0;
shapelayer.lineJoin = kCALineJoinMiter;
shapelayer.lineDashPattern = [NSArray arrayWithObjects:[NSNumber numberWithInt:10],[NSNumber numberWithInt:7], nil];
shapelayer.lineDashPhase = 3.0f;
shapelayer.path = path.CGPath;
Note: This answer provides a hint so you can improvise accordingly to your requirement(s).
Note: The code from Prince did really help me out, so I will give him +10 for the tips. But in the end, I add to come with my own code. I will also add some context to it, so it can be useful for future readers
The final code was like this:
-(void)updateLine{
// Important, otherwise we will be adding multiple sub layers
if ([[[self layer] sublayers] objectAtIndex:0])
{
self.layer.sublayers = nil;
}
CAShapeLayer *shapeLayer = [CAShapeLayer layer];
[shapeLayer setBounds:self.bounds];
[shapeLayer setPosition:self.center];
[shapeLayer setFillColor:[[UIColor clearColor] CGColor]];
[shapeLayer setStrokeColor:[[UIColor blackColor] CGColor]];
[shapeLayer setLineWidth:3.0f];
[shapeLayer setLineJoin:kCALineJoinRound];
[shapeLayer setLineDashPattern:
[NSArray arrayWithObjects:[NSNumber numberWithInt:10],
[NSNumber numberWithInt:5],nil]];
// Setup the path
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, beginPoint.center.x, beginPoint.center.y);
CGPathAddLineToPoint(path, NULL, endPoint.center.x, endPoint.center.y);
[shapeLayer setPath:path];
CGPathRelease(path);
[[self layer] addSublayer:shapeLayer];
}
In my case, the beginPoint and endPoint are movable by the user, by using KVO. So when one of them moves:
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if ([keyPath isEqual:@"position"])
{
[self updateLine];
}
}
I did play a lot with Prince's code. I tried on the draw: method, which add a thin line between the dashed line (a bit weird...) and I also tried on initWithFrame:. By itself his code, without any modifications, would give me this kind of errors on the console:
<Error>: CGContextSaveGState: invalid context 0x0
<Error>: CGContextSetLineWidth: invalid context 0x0
<Error>: CGContextSetLineJoin: invalid context 0x0
<Error>: CGContextSetLineCap: invalid context 0x0
<Error>: CGContextSetMiterLimit: invalid context 0x0
<Error>: CGContextSetFlatness: invalid context 0x0
<Error>: CGContextAddPath: invalid context 0x0
<Error>: CGContextDrawPath: invalid context 0x0
<Error>: CGContextRestoreGState: invalid context 0x0
Dash Line in Swift4 • Xcode 9
Crate a CAShapeLayer & use lineDashPattern
extension UIView {
func addDashedBorder() {
//Create a CAShapeLayer
let shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.lineWidth = 2
// passing an array with the values [2,3] sets a dash pattern that alternates between a 2-user-space-unit-long painted segment and a 3-user-space-unit-long unpainted segment
shapeLayer.lineDashPattern = [2,3]
let path = CGMutablePath()
path.addLines(between: [CGPoint(x: 0, y: 0),
CGPoint(x: self.frame.width, y: 0)])
shapeLayer.path = path
layer.addSublayer(shapeLayer)
}
}
Usage:
dashView.addDashedBorder()
Output:
Swift 2.2
dropping this in here to save others time..
extension UIView {
func addDashedLine(color: UIColor = UIColor.lightGrayColor()) {
layer.sublayers?.filter({ $0.name == "DashedTopLine" }).map({ $0.removeFromSuperlayer() })
self.backgroundColor = UIColor.clearColor()
let cgColor = color.CGColor
let shapeLayer: CAShapeLayer = CAShapeLayer()
let frameSize = self.frame.size
let shapeRect = CGRect(x: 0, y: 0, width: frameSize.width, height: frameSize.height)
shapeLayer.name = "DashedTopLine"
shapeLayer.bounds = shapeRect
shapeLayer.position = CGPoint(x: frameSize.width / 2, y: frameSize.height / 2)
shapeLayer.fillColor = UIColor.clearColor().CGColor
shapeLayer.strokeColor = cgColor
shapeLayer.lineWidth = 1
shapeLayer.lineJoin = kCALineJoinRound
shapeLayer.lineDashPattern = [4, 4]
let path: CGMutablePathRef = CGPathCreateMutable()
CGPathMoveToPoint(path, nil, 0, 0)
CGPathAddLineToPoint(path, nil, self.frame.width, 0)
shapeLayer.path = path
self.layer.addSublayer(shapeLayer)
}
}
Here is Swift 3 version of Alexandre G's answer https://stackoverflow.com/a/38194152/1800489
extension UIView {
func addDashedLine(color: UIColor = .lightGray) {
layer.sublayers?.filter({ $0.name == "DashedTopLine" }).map({ $0.removeFromSuperlayer() })
backgroundColor = .clear
let shapeLayer = CAShapeLayer()
shapeLayer.name = "DashedTopLine"
shapeLayer.bounds = bounds
shapeLayer.position = CGPoint(x: frame.width / 2, y: frame.height / 2)
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.strokeColor = color.cgColor
shapeLayer.lineWidth = 1
shapeLayer.lineJoin = kCALineJoinRound
shapeLayer.lineDashPattern = [4, 4]
let path = CGMutablePath()
path.move(to: CGPoint.zero)
path.addLine(to: CGPoint(x: frame.width, y: 0))
shapeLayer.path = path
layer.addSublayer(shapeLayer)
}
}
The accepted answer has a coordinate problem. The line will be drawn some distance below. And I cannot figure out why and how much distance it increases on Y coordinate.
There's a way to draw a dashed line with correct coordinate:
-(void)drawRect:(CGRect)rect
{
CGContextBeginPath(cx);
CGContextRef cx = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(cx, _thickness);
CGContextSetStrokeColorWithColor(cx, _color.CGColor);
CGFloat dash[] = {_dashedLength,_dashedGap};
CGContextSetLineDash(cx, 0, dash, 2); // nb "2" == ra count
// CGContextSetLineCap(cx, kCGLineCapRound);
CGContextMoveToPoint(cx, 0, _thickness);
CGContextAddLineToPoint(cx, self.bounds.size.width, _thickness);
CGContextStrokePath(cx);
CGContextClosePath(cx);
}
This answer is from Draw dotted (not dashed!) line, with IBDesignable in 2017. DON'T DON'T DON'T forget to set the background color as white when you want a black dashed line!! By default the view has a black background color, and the line color is also black, so I thought it was a solid line. It cost me half a day to find out. T_T
First all the credit goes to RuiAAPeres and Prince, I'm just encapsulating their answers into a UIView object that others can drop into their projects and use
#import <UIKit/UIKit.h>
/**
* Simple UIView for a dotted line
*/
@interface H3DottedLine : UIView
/**
* Set the line's thickness
*/
@property (nonatomic, assign) CGFloat thickness;
/**
* Set the line's color
*/
@property (nonatomic, copy) UIColor *color;
/**
* Set the length of the dash
*/
@property (nonatomic, assign) CGFloat dashedLength;
/**
* Set the gap between dashes
*/
@property (nonatomic, assign) CGFloat dashedGap;
@end
@implementation H3DottedLine
#pragma mark - Object Lifecycle
- (instancetype)init {
self = [super init];
if (self) {
// Set Default Values
_thickness = 1.0f;
_color = [UIColor whiteColor];
_dashedGap = 1.0f;
_dashedLength = 5.0f;
}
return self;
}
#pragma mark - View Lifecycle
- (void)layoutSubviews {
// Note, this object draws a straight line. If you wanted the line at an angle you simply need to adjust the start and/or end point here.
[self updateLineStartingAt:self.frame.origin andEndPoint:CGPointMake(self.frame.origin.x+self.frame.size.width, self.frame.origin.y)];
}
#pragma mark - Setters
- (void)setThickness:(CGFloat)thickness {
_thickness = thickness;
[self setNeedsLayout];
}
- (void)setColor:(UIColor *)color {
_color = [color copy];
[self setNeedsLayout];
}
- (void)setDashedGap:(CGFloat)dashedGap {
_dashedGap = dashedGap;
[self setNeedsLayout];
}
- (void)setDashedLength:(CGFloat)dashedLength {
_dashedLength = dashedLength;
[self setNeedsLayout];
}
#pragma mark - Draw Methods
-(void)updateLineStartingAt:(CGPoint)beginPoint andEndPoint:(CGPoint)endPoint {
// Important, otherwise we will be adding multiple sub layers
if ([[[self layer] sublayers] objectAtIndex:0]) {
self.layer.sublayers = nil;
}
CAShapeLayer *shapeLayer = [CAShapeLayer layer];
[shapeLayer setBounds:self.bounds];
[shapeLayer setPosition:self.center];
[shapeLayer setFillColor:[UIColor clearColor].CGColor];
[shapeLayer setStrokeColor:self.color.CGColor];
[shapeLayer setLineWidth:self.thickness];
[shapeLayer setLineJoin:kCALineJoinRound];
[shapeLayer setLineDashPattern:@[@(self.dashedLength), @(self.dashedGap)]];
// Setup the path
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, beginPoint.x, beginPoint.y);
CGPathAddLineToPoint(path, NULL, endPoint.x, endPoint.y);
[shapeLayer setPath:path];
CGPathRelease(path);
[[self layer] addSublayer:shapeLayer];
}
@end
Update Swift 5 & UIBezierPath
For those working with UIBezierPath instead of CAShapeLayer, here is how to achieve it
class MyView: UIView {
override func draw(_ rect: CGRect) {
let path = UIBezierPath()
// >> define the pattern & apply it
let dashPattern: [CGFloat] = [4.0, 4.0]
path.setLineDash(dashPattern, count: dashPattern.count, phase: 0)
// <<
path.lineWidth = 1
path.move(to: CGPoint(x: 0, y: 0))
path.addLine(to: CGPoint(x: 100, y: 100))
path.stroke()
}
}
As said many times in this thread, you can play with the pattern and the phase to achieve a complex dotted line.
Hope this helps
来源：https://stackoverflow.com/questions/12091916/uiview-with-a-dashed-line