Question

i added a custom view and want to draw an inner smaller circle, outer bigger circle and and perpendicular line. the drawRect: method in my class looks like this.

- (void) drawRect:(CGRect)rect{
    CGContextRef myContext = UIGraphicsGetCurrentContext();
    float height = rect.size.height;
    float width = rect.size.width;
    CGContextTranslateCTM(myContext, 0.0, height);
    CGContextScaleCTM(myContext, 1.0, -1.0);
    CGPoint middle = CGPointMake(width/2, height/2);
    UIBezierPath *innerCirclePath = [UIBezierPath bezierPathWithArcCenter:middle radius:25 startAngle:0 endAngle:DEGREES_TO_RADIANS(360) clockwise:YES];
    [innerCirclePath setLineWidth:2];
    [[UIColor redColor] setStroke];
    [innerCirclePath stroke];
    UIBezierPath *outerCirclePath = [UIBezierPath bezierPathWithArcCenter:middle radius:120 startAngle:0 endAngle:DEGREES_TO_RADIANS(360) clockwise:NO];
    [outerCirclePath setLineWidth:2];
    [[UIColor greenColor] setStroke];
    [outerCirclePath stroke];
    UIBezierPath *xAxis = [UIBezierPath bezierPath];
    [xAxis moveToPoint:CGPointMake(width, height/2 - 150)];
    [xAxis addLineToPoint:CGPointMake(width, height/2 + 150)];
    [xAxis closePath];
    [[UIColor grayColor] setStroke];
    [xAxis setLineWidth:2];
    [xAxis stroke];
}

Now I do get the circles, both outer and inner but there is no perpendicular line that I wanted. Why is it not getting drawn?

Answer 1

You’re using these two lines to set up the path for your “perpendicular line”:

[xAxis moveToPoint:CGPointMake(width, height/2 - 150)];
[xAxis addLineToPoint:CGPointMake(width, height/2 + 150)];

The problem is that the X coordinate of both points is the right edge of your view. Perhaps you want it to be at the center of your view:

CGFloat xMid = CGRectGetMidX(rect);
[xAxis moveToPoint:CGPointMake(xMid, height/2 - 150)];
[xAxis addLineToPoint:CGPointMake(xMid, height/2 + 150)];