问题
I'm trying to draw a line between two points using a CALayer. Here is my code:
//positions a CALayer to be a line between a parent node and its subnodes.
-(void)makeLineLayer:(CALayer *)layer lineFromPointA:(CGPoint)pointA toPointB:(CGPoint)pointB{
NSLog([NSString stringWithFormat:@"Coordinates: \n Ax: %f Ay: %f Bx: %f By: %f", pointA.x,pointA.y,pointB.x,pointB.y]);
//find the length of the line:
CGFloat length = sqrt((pointA.x - pointB.x) * (pointA.x - pointB.x) + (pointA.y - pointB.y) * (pointA.y - pointB.y));
layer.frame = CGRectMake(0, 0, 1, length);
//calculate and set the layer's center:
CGPoint center = CGPointMake((pointA.x+pointB.x)/2, (pointA.y+pointB.y)/2);
layer.position = center;
//calculate the angle of the line and set the layer's transform to match it.
CGFloat angle = atan2f(pointB.y - pointA.y, pointB.x - pointA.x);
layer.transform = CATransform3DMakeRotation(angle, 0, 0, 1);
}
I know that the length is being calculated correctly, and I'm am pretty sure that the center is also. When I run it lines are displayed that are the right length and that pass through the center point between the two points, but are not rotated correctly. At first I thought that the line was being rotated around the wrong anchor point, so I did: layer.anchorPoint = center;
, but this code fails to show any lines on the screen. What am I doing wrong
回答1:
Try This...
-(void)makeLineLayer:(CALayer *)layer lineFromPointA:(CGPoint)pointA toPointB:(CGPoint)pointB
{
CAShapeLayer *line = [CAShapeLayer layer];
UIBezierPath *linePath=[UIBezierPath bezierPath];
[linePath moveToPoint: pointA];
[linePath addLineToPoint:pointB];
line.path=linePath.CGPath;
line.fillColor = nil;
line.opacity = 1.0;
line.strokeColor = [UIColor redColor].CGColor;
[layer addSublayer:line];
}
回答2:
Here's a Swift version based on Rajesh Choudhary's answer:
Swift 2
func drawLine(onLayer layer: CALayer, fromPoint start: CGPoint, toPoint end: CGPoint) {
let line = CAShapeLayer()
let linePath = UIBezierPath()
linePath.moveToPoint(start)
linePath.addLineToPoint(end)
line.path = linePath.CGPath
line.fillColor = nil
line.opacity = 1.0
line.strokeColor = UIColor.redColor().CGColor
layer.addSublayer(line)
}
Swift 3
func drawLine(onLayer layer: CALayer, fromPoint start: CGPoint, toPoint end: CGPoint) {
let line = CAShapeLayer()
let linePath = UIBezierPath()
linePath.move(to: start)
linePath.addLine(to: end)
line.path = linePath.cgPath
line.fillColor = nil
line.opacity = 1.0
line.strokeColor = UIColor.red.cgColor
layer.addSublayer(line)
}
回答3:
Here's a Swift 3 version based on Rajesh Choudhary's answer:
func drawLine(onLayer layer: CALayer, fromPoint start: CGPoint, toPoint end:CGPoint) {
let line = CAShapeLayer()
let linePath = UIBezierPath()
linePath.move(to: start)
linePath.addLine(to: end)
line.path = linePath.cgPath
line.fillColor = nil
line.opacity = 1.0
line.strokeColor = UIColor.green.cgColor
layer.addSublayer(line)
}
来源:https://stackoverflow.com/questions/21515451/draw-a-line-with-a-calayer