Draw UIView based on CGPoint on screen - ios

Question

I have four small circles on screen in a random position. These small circles could be anywhere on the screen and are in front on a MapView.
How can I create a shape based on those circles ?
Also, the user can press a Button to randomly change the position of the circles, so the shape have to recreated.
So far, I'm reading about UIBezierPath and I'm able to create a shape based on points but I can't doing dinamically.
UIBezierPath* bezierPath = [UIBezierPath bezierPath];
[bezierPath moveToPoint: CGPointMake(52, 33)];
[bezierPath addLineToPoint: CGPointMake(145, 19)];
[bezierPath addLineToPoint: CGPointMake(158, 79)];
[bezierPath addLineToPoint: CGPointMake(66, 103)];
[UIColor.grayColor setFill];
[bezierPath fill];

Answer 1

What you could do is adding a UIImageView with a transparent background color as a subview of your MapView ( the image view should have the same frame as your map view ).
In viewDidLoad, you can begin an imageContext, using :
UIGraphicsBeginImageContext(self.imageView.frame.size)
Then, you can draw lines between your points, using CGMutablePath :
func drawLines()
{
let point1 = CGPointMake(20, 100)
let point2 = CGPointMake(230, 150)
let point3 = CGPointMake(40, 340)
let points = [point1, point2, point3]
let context = UIGraphicsGetCurrentContext()
CGContextClearRect(context, self.imageView.frame)
let pathRef = CGPathCreateMutable();
for var i = 0; i < points.count; i++
{
let point = points[i]
if i == 0
{
CGPathMoveToPoint(pathRef, nil, point.x, point.y)
}
else
{
CGPathAddLineToPoint(pathRef, nil, point.x, point.y)
}
}
CGContextSetLineWidth(context, 5.0)
CGPathCloseSubpath(pathRef)
CGContextAddPath(context, pathRef);
CGContextSetStrokeColorWithColor(context, UIColor.brownColor().CGColor)
CGContextStrokePath(context)
let image = UIGraphicsGetImageFromCurrentImageContext()
self.imageView.image = image
}
Of course, you should adapt this method to your needs, but this would work dynamically.
It's not the only solution. If you want to get to know Core Graphics a bit more, you should read some documentation. It can be pretty powerful.