How to draw line following user finger move

Question

Code:

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    UIColor *grayColor = [UIColor colorWithRed: 0.8980392157 green: 0.8980392157 blue: 0.8980392157 alpha: 1.0];

    [grayColor set];

    CGContextSetLineWidth(context, 2.0);
    CGContextStrokeEllipseInRect(context, CGRectMake(100, 190, 101, 101));
}

I did draw a circle.When user moves finger on it i want to draw line on it.I googled lot about this.But i could not find any solution.any help will be appreciated.thanks in advance.

Check this http://stackoverflow.com/questions/16846413/how-do-you-draw-a-line-programmatically-from-a-view-controller — DipakSonara, May 29 '14 at 12:19
please check this http://www.raywenderlich.com/18840/how-to-make-a-simple-drawing-app-with-uikit — Nitin Gohel, May 29 '14 at 12:24
https://www.cocoacontrols.com/controls/jbsignaturecontroller — Pawan Sharma, May 29 '14 at 12:24

score 0 · Answer 1 · answered May 29 '14 at 12:20

You should look into these:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

These are the methods to track the touches of a UIView.

score 0 · Answer 2 · answered May 29 '14 at 12:27

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

        UITouch *touch = [touches anyObject];
        CGPoint tapLocation = [touch locationInView:self.superDrawingLayer];  
        lastPoint = tapLocation;
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
        UITouch *touch = [touches anyObject];
        CGPoint tapLocation = [touch locationInView:self.superDrawingLayer];
        currentPoint = tapLocation;

        UIGraphicsBeginImageContext(self.superDrawingLayer.frame.size);
        [self.superDrawingLayer.image drawInRect:CGRectMake(0, 0, self.superDrawingLayer.frame.size.width, self.superDrawingLayer.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), drwaingWidth);
        CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeColor);
        CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [[UIColor colorWithRed:1.0f green:0.764705f blue:0 alpha:1.0] CGColor]);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        CGContextFlush(UIGraphicsGetCurrentContext());


        self.superDrawingLayer.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

        lastPoint = tapLocation;
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{

}

//Here superDrawingLayer is the ImageView on which lines will be drawn.

How to draw line following user finger move

2 Answers2