Draw Triangle iOS - ios

Question

The code below is drawing me a circle, how can I modify the existing code to draw a triangle instead?
_colorDotLayer = [CALayer layer];
CGFloat width = self.bounds.size.width-6;
_colorDotLayer.bounds = CGRectMake(0, 0, width, width);
_colorDotLayer.allowsGroupOpacity = YES;
_colorDotLayer.backgroundColor = self.annotationColor.CGColor;
_colorDotLayer.cornerRadius = width/2;
_colorDotLayer.position = CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2);

Answer 1

While there are shown several Core Graphics solution, I want to add a Core Animation based solution.
- (void)viewDidLoad
{
[super viewDidLoad];
UIBezierPath* trianglePath = [UIBezierPath bezierPath];
[trianglePath moveToPoint:CGPointMake(0, view3.frame.size.height-100)];
[trianglePath addLineToPoint:CGPointMake(view3.frame.size.width/2,100)];
[trianglePath addLineToPoint:CGPointMake(view3.frame.size.width, view2.frame.size.height)];
[trianglePath closePath];
CAShapeLayer *triangleMaskLayer = [CAShapeLayer layer];
[triangleMaskLayer setPath:trianglePath.CGPath];
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0,0, size.width, size.height)];
view.backgroundColor = [UIColor colorWithWhite:.75 alpha:1];
view.layer.mask = triangleMaskLayer;
[self.view addSubview:view];
}
code based on my blog post.

Answer 2

#implementation TriangleView {
CAShapeLayer *_colorDotLayer;
}
- (void)layoutSubviews {
[super layoutSubviews];
if (_colorDotLayer == nil) {
_colorDotLayer = [CAShapeLayer layer];
_colorDotLayer.fillColor = self.annotationColor.CGColor;
[self.layer addSublayer:_colorDotLayer];
}
CGRect bounds = self.bounds;
CGFloat radius = (bounds.size.width - 6) / 2;
CGFloat a = radius * sqrt((CGFloat)3.0) / 2;
CGFloat b = radius / 2;
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(0, -radius)];
[path addLineToPoint:CGPointMake(a, b)];
[path addLineToPoint:CGPointMake(-a, b)];
[path closePath];
[path applyTransform:CGAffineTransformMakeTranslation(CGRectGetMidX(bounds), CGRectGetMidY(bounds))];
_colorDotLayer.path = path.CGPath;
}
- (void)awakeFromNib {
[super awakeFromNib];
self.annotationColor = [UIColor redColor];
}
#end
Result:

Answer 3

I think is more easy than this solutions:
UIBezierPath *path = [UIBezierPath new];
[path moveToPoint:(CGPoint){20, 0}];
[path addLineToPoint:(CGPoint){40, 40}];
[path addLineToPoint:(CGPoint){0, 40}];
[path addLineToPoint:(CGPoint){20, 0}];
// Create a CAShapeLayer with this triangular path
// Same size as the original imageView
CAShapeLayer *mask = [CAShapeLayer new];
mask.frame = self.viewTriangleCallout.bounds;
mask.path = path.CGPath;
This is my white triangle:
You can change points or rotate if you want:
UIBezierPath *path = [UIBezierPath new];
[path moveToPoint:(CGPoint){0, 0}];
[path addLineToPoint:(CGPoint){40, 0}];
[path addLineToPoint:(CGPoint){20, 20}];
[path addLineToPoint:(CGPoint){0, 0}];
// Create a CAShapeLayer with this triangular path
// Same size as the original imageView
CAShapeLayer *mask = [CAShapeLayer new];
mask.frame = self.viewTriangleCallout.bounds;
mask.path = path.CGPath;

Answer 4

Example code, it is based on this SO Answer which draws stars:
#implementation TriangleView
-(void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
int sides = 3;
double size = 100.0;
CGPoint center = CGPointMake(160.0, 100.0);
double radius = size / 2.0;
double theta = 2.0 * M_PI / sides;
CGContextMoveToPoint(context, center.x, center.y-radius);
for (NSUInteger k=1; k<sides; k++) {
float x = radius * sin(k * theta);
float y = radius * cos(k * theta);
CGContextAddLineToPoint(context, center.x+x, center.y-y);
}
CGContextClosePath(context);
CGContextFillPath(context); // Choose for a filled triangle
// CGContextSetLineWidth(context, 2); // Choose for a unfilled triangle
// CGContextStrokePath(context); // Choose for a unfilled triangle
}
#end

Answer 5

Use UIBezeierPaths
CGFloat radius = 20;
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, (center.x + bottomLeft.x) / 2, (center.y + bottomLeft.y) / 2);
CGPathAddArcToPoint(path, NULL, bottomLeft.x, bottomLeft.y, bottomRight.x, bottomRight.y, radius);
CGPathAddArcToPoint(path, NULL, bottomRight.x, bottomRight.y, center.x, center.y, radius);
CGPathAddArcToPoint(path, NULL, center.x, center.y, bottomLeft.x, bottomLeft.y, radius);
CGPathCloseSubpath(path);
UIBezierPath *bezierPath = [UIBezierPath bezierPathWithCGPath:path];
CGPathRelease(path);