使用CALayer绘制线 [英] Draw a line with a CALayer

问题描述

我想使用CALayer在两点之间画一条线。这是我的代码：

//将CALayer定位为父节点及其子节点之间的线。

   - （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] 
 
 //找到行的长度：
 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）; 
 
 //计算并设置图层的中心：
 CGPoint center = CGPointMake（pointA.x + pointB.x）/ 2，（pointA.y + pointB.y）/ 2） ; 
 layer.position = center; 
 
 //计算线的角度并设置图层的变换以匹配它。 
 CGFloat angle = atan2f（pointB.y  -  pointA.y，pointB.x  -  pointA.x）; 
 layer.transform = CATransform3DMakeRotation（angle，0，0，1）; 
} 
  

我知道长度正确计算，确定中心也是。当我运行它显示线是正确的长度，通过两点之间的中心点，但不能正确旋转。起初我以为这条线绕着错误的锚点旋转，所以我做了： layer.anchorPoint = center; ，但是这个代码没有显示任何行屏幕。

<$ p

$ p> - （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];
}


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

解决方案

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];
}

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