How to Draw a Single Point Line in iOS

How to Draw a single point line in iOS

I did the same with a UIView category. Here are my methods :

#define SEPARATOR_HEIGHT 0.5

- (void)addSeparatorLinesWithColor:(UIColor *)color
{
    [self addSeparatorLinesWithColor:color edgeInset:UIEdgeInsetsZero];
}

- (void)addSeparatorLinesWithColor:(UIColor *)color edgeInset:(UIEdgeInsets)edgeInset
{

    UIView *topSeparatorView = [[UIView alloc] initWithFrame:CGRectMake(edgeInset.left, - SEPARATOR_HEIGHT, self.frame.size.width - edgeInset.left - edgeInset.right, SEPARATOR_HEIGHT)];
    [topSeparatorView setBackgroundColor:color];
    [self addSubview:topSeparatorView];

    UIView *separatorView = [[UIView alloc] initWithFrame:CGRectMake(edgeInset.left, self.frame.size.height + SEPARATOR_HEIGHT, self.frame.size.width - edgeInset.left - edgeInset.right, SEPARATOR_HEIGHT)];
    [separatorView setBackgroundColor:color];
    [self addSubview:separatorView];
}

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Just to add to Rémy's great answer, it's perhaps even simpler to do this. Make a class UILine.m

@interface UILine:UIView
@end
@implementation UILine
-(id)awakeFromNib
    {
    // careful, contentScaleFactor does NOT WORK in storyboard during initWithCoder.
    // example, float sortaPixel = 1.0/self.contentScaleFactor ... does not work.
    // instead, use mainScreen scale which works perfectly:
    float sortaPixel = 1.0/[UIScreen mainScreen].scale;
    UIView *topSeparatorView = [[UIView alloc] initWithFrame:
        CGRectMake(0, 0, self.frame.size.width, sortaPixel)];

    topSeparatorView.userInteractionEnabled = NO;
    [topSeparatorView setBackgroundColor:self.backgroundColor];
    [self addSubview:topSeparatorView];

    self.backgroundColor = [UIColor clearColor];
    self.userInteractionEnabled = NO;
    }
@end

In IB, drop in a UIView, click identity inspector and rename the class to a UILine. Set the width you want in IB. Set the height to 1 or 2 pixels - simply so you can see it in IB. Set the background colour you want in IB. When you run the app it will become a 1-pixel line, that width, in that colour. (You probably should not be affected by any default autoresize settings in storyboard/xib, I couldn't make it break.) You're done.

Note: you may think "Why not just resize the UIView in code in awakeFromNib?" Resizing views upon loading, in a storyboard app, is problematic - see the many questions here about it!

Interesting gotchya: it's likely you'll just make the UIView, say, 10 or 20 pixels high on the storyboard, simply so you can see it. Of course it disappears in the app and you get the pretty one pixel line. But! be sure to remember self.userInteractionEnabled = NO, or it might get over your other, say, buttons!

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2016 solution ! https://stackoverflow.com/a/34766567/294884

How to draw a single point (Swift)

Now, you just need to take that location and add a view there. Try to update touchesBegan to look something like this:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch in touches {
        let location = touch.location(in: self.view)
        xpoint = location.x
        ypoint = location.y

        //Initialize the view at the correct spot
        //We set the view's frame by giving it an origin (that's the CGPoint we build from the x and y coordinates) and giving it a size, which can be anything really
        let pointView = UIView(frame: CGRect(origin: CGPoint(x: xpoint, y: ypoint), size: CGSize(width: 25, height: 25))

        //Round the view's corners so that it is a circle, not a square
        view.layer.cornerRadius = 12.5

        //Give the view a background color (in this case, blue)
        view.backgroundColor = .blue

        //Add the view as a subview of the current view controller's view
        self.view.addSubview(view)
    }
}

How to draw a line from one point to the next point in Swift

Based On your code I changed some things and this code Works please check.

    class ViewController: UIViewController {

        var lastPosition: CGPoint?
        override func viewDidLoad() {
            super.viewDidLoad()
            // Do any additional setup after loading the view.
            // Gesture Code
        }

        override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
            if let touch = touches.first{

                let position = touch.location(in: view)
            if let lastPosition = self.lastPosition {
                self.drawLineFromPoint(start: lastPosition, toPoint: position, ofColor: UIColor.red, inView: self.view)
            }
                self.lastPosition = position
                // View the x and y coordinates
                let dot = UIView(frame: CGRect(x: position.x, y: position.y, width: 10, height: 10))
                dot.backgroundColor = .red
                view.addSubview(dot)
                print(position)

            }
        }

        override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
            if let touch = touches.first, let lastPosition = self.lastPosition{

                let position = touch.location(in: view)
                self.drawLineFromPoint(start: lastPosition, toPoint: position, ofColor: UIColor.red, inView: self.view)
                self.lastPosition = position
                let dot = UIView(frame: CGRect(x: position.x, y: position.y, width: 10, height: 10))
                dot.backgroundColor = .red
                view.addSubview(dot)
            }
        }

        //Not sure how to do this part ???
        func drawLineFromPoint(start : CGPoint, toPoint end:CGPoint, ofColor lineColor: UIColor, inView view:UIView) {

            let path = UIBezierPath()
            path.move(to: start)
            path.addLine(to: end)

            let shapeLayer = CAShapeLayer()
            shapeLayer.path = path.cgPath
            shapeLayer.strokeColor = UIColor.green.cgColor
            shapeLayer.lineWidth = 1.0

            view.layer.addSublayer(shapeLayer)
        }

    }

How to draw a line in line chart for single value in Charts(IOS)

The library cannot do this automatically, but there is the following option.

You check if your data contains exactly one point. If yes, then you add a so called LimitLine.

For example:

let limitLine = ChartLimitLine(
   limit: value,
   label: labelText)

limitLine.lineColor = .blue
limitLine.labelPosition = .topLeft
limitLine.valueFont = UIFont.systemFont(ofSize: 14)

chartView.leftAxis.addLimitLine(limitLine)

How to draw a line in the simplest way in swift

Try looking into UIBezierPath, it will help you a lot for drawing lines. Here is documentation. Here is an example:

override func drawRect(rect: CGRect) {
    let aPath = UIBezierPath()

    aPath.move(to: CGPoint(x:<#start x#>, y:<#start y#>))
    aPath.addLine(to: CGPoint(x: <#end x#>, y: <#end y#>))

    // Keep using the method addLine until you get to the one where about to close the path
    aPath.close()

    // If you want to stroke it with a red color
    UIColor.red.set()
    aPath.lineWidth = <#line width#>
    aPath.stroke()
}

Make sure you put this code in the drawRect, like in the example above.

If you need to update the drawing just call setNeedsDisplay() to update.

How to draw line given a center point and angle in iOS?

This begins with simple trigonometry. You need to calculate the x and y coordinate of the 2nd point. With an origin of 0,0 and treating a line that goes straight to the right as 0 degrees, and going counterclockwise (anti-clockwise for some of you), you do:

double angle = ... // angle in radians
double newX = cos(angle);
double newY = sin(angle);

This assumes a radius of 1. Multiply each times a desired radius. Pick a number that will be bigger than the screen such as 480 for an iPhone or 1024 for an iPad (assuming you want points and not pixels).

Then add the original point to get the final point.

Assuming you have CGPoint start, double angle, and a length, your final point is:

double endX = cos(angle) * length + start.x;
double endY = sin(angle) * length + start.y;
CGPoint end = CGPointMake(endX, endY);

It's OK if the end point is off the screen.

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