Drawing semicircles with CoreGraphics
I know how to draw lines and shapes with CGPath
. But I could not figure out how to draw this symbol for the electrical circuit
What code should you write to get a semi-circular shape?
This is what I have so far:
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 5.0);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextMoveToPoint(context, 60, 80);
CGContextAddLineToPoint(context, 120, 80);
CGContextMoveToPoint(context, 120, 80);
CGContextAddArc(120,80,M_PI,M_PI/2);
CGContextMoveToPoint(context, 200, 80);
CGContextAddLineToPoint(context, 300, 80);
CGContextStrokePath(context);
}
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You can create UIBezierPath
for example. something like:
UIBezierPath *path = [UIBezierPath bezierPath];
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 15.0;
CGFloat lineLength = 25.0;
[path moveToPoint:point];
point.x += lineLength;
[path addLineToPoint:point];
point.x += radius;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += lineLength + radius;
[path addLineToPoint:point];
Maybe your view controller will just create CAShapeLayer
and add it to your view layer
.
CAShapeLayer *layer = [CAShapeLayer layer];
layer.path = [path CGPath];
layer.lineWidth = 2.0;
layer.fillColor = [[UIColor clearColor] CGColor];
layer.strokeColor = [[UIColor blackColor] CGColor];
[self.view.layer addSublayer:layer];
If you want to do it in a drawRect
subclass UIView
, you can, stroke
this way:
- (void)drawRect:(CGRect)rect
{
UIBezierPath *path = [UIBezierPath bezierPath];
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 20.0;
CGFloat lineLength = 45.0;
[path moveToPoint:point];
point.x += lineLength;
[path addLineToPoint:point];
point.x += radius;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += lineLength + radius;
[path addLineToPoint:point];
path.lineWidth = 2.0;
[[UIColor blackColor] setStroke];
[[UIColor clearColor] setFill];
[path stroke];
}
Or, as your revised question suggests, if you're more comfortable with CoreGraphics, you can do this too:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 20.0;
CGFloat lineLength = 45.0;
CGContextMoveToPoint(context, point.x, point.y);
point.x += lineLength;
CGContextAddLineToPoint(context, point.x, point.y);
point.x += radius;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += lineLength + radius;
CGContextAddLineToPoint(context, point.x, point.y);
CGContextSetStrokeColorWithColor(context, [[UIColor blackColor] CGColor]);
CGContextSetLineWidth(context, 2.0);
CGContextDrawPath(context, kCGPathStroke);
}
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