Question

I currently have the following code to try and allow the user to draw a dotted path and make a custom shape. Once they have made this shape, I wanted it to automatically be filled with colour. That isn’t happening.

At the moment I am getting this error for the code below:

<Error>: CGContextClosePath: no current point.

Here’s the code I’m using:

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

UITouch *touch = [touches anyObject];

CGPoint previous = [touch previousLocationInView:self];
CGPoint current = [touch locationInView:self];

#define SQR(x) ((x)*(x))
//Check for a minimal distance to avoid silly data
if ((SQR(current.x - self.previousPoint2.x) + SQR(current.y - self.previousPoint2.y)) > SQR(10))
{

    float dashPhase = 5.0;
    float dashLengths[] = {10, 10};
    CGContextSetLineDash(context,
                         dashPhase, dashLengths, 2);

    CGContextSetFillColorWithColor(context, [[UIColor lightGrayColor] CGColor]);
    CGContextFillPath(context);

    CGContextSetLineWidth(context, 2);
    CGFloat gray[4] = {0.5f, 0.5f, 0.5f, 1.0f};
    CGContextSetStrokeColor(context, gray);

    self.brushSize = 5;
    self.brushColor = [UIColor lightGrayColor];

    self.previousPoint2 = self.previousPoint1;
    self.previousPoint1 = previous;
    self.currentPoint = current;

    // calculate mid point
    self.mid1 = [self pointBetween:self.previousPoint1 andPoint:self.previousPoint2];
    self.mid2 = [self pointBetween:self.currentPoint andPoint:self.previousPoint1];

    if(self.paths.count == 0)
    {

    UIBezierPath* newPath = [UIBezierPath bezierPath];

    CGContextBeginPath(context);

    [newPath moveToPoint:self.mid1];
    [newPath addLineToPoint:self.mid2];
    [self.paths addObject:newPath];

    CGContextClosePath(context);

    }

    else

    {

        UIBezierPath* lastPath = [self.paths lastObject];

        CGContextBeginPath(context);

        [lastPath addLineToPoint:self.mid2];
        [self.paths replaceObjectAtIndex:[self.paths indexOfObject:[self.paths lastObject]] withObject:lastPath];

        CGContextClosePath(context);

    }

    //Save
    [self.pathColors addObject:self.brushColor];

    self.needsToRedraw = YES;
  [self setNeedsDisplayInRect:[self dirtyRect]];
  //[self setNeedsDisplay];
}

}

Why is this happening and why is the inside of the path not being filled with colour?

Answer 1

Your code has a few issues:

• You should be doing your drawing in your view’s drawRect: method, not the touch handler.
• You never set the variable context with a value for the current context. Do that with the UIGraphicsGetCurrentContext() method. Again, within your drawRect: method.
• You go through the trouble of creating a UIBezierPath object, but you never use it. Do that by calling CGContextAddPath( context, newPath.CGPath ), changing the variable name as needed in the two places you appear to the using a UIBezierPath.
• Keep the call to setNeedsDisplayInRect: in your touch handler method. That tells the system to do the work to update your view using the drawing that your (yet to be implemented) drawRect: method draws.