CAShapeLayer 与贝塞尔曲线

一 CAShapeLayer 简介

1，CAShapeLayer继承至CALayer，可以使用CALayer的所有属性

2，CAShapeLayer需要与贝塞尔曲线配合使用才有意义；单独使用毫无意义

3，使用CAShapeLayer与贝塞尔可以实现不在view的drawRect方法中画出一些想要的图形；

4，CAShapeLayer属于Core  Animation框架，其动画渲染直接提交到手机的GPU当中，相较于view的drawRect方法使用CPU渲染而言，其效率极高，

能大大优化内存使用情况。

drawRect 属于Core Graphics 框架，走CPU，耗性能较大。

5，示例：

@interface SubLayerVC ()

@property (nonatomic, strong) NSTimer      *timer;
@property (nonatomic, strong) CAShapeLayer *shapeLayer;

@end

@implementation SubLayerVC

- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    // 创建shapeLayer
    _shapeLayer = [CAShapeLayer layer];
    _shapeLayer.frame         = (CGRect){CGPointMake(, ), CGSizeMake(, )};
    _shapeLayer.position      = self.view.center;
    _shapeLayer.path          = [self getStar1BezierPath].CGPath;
    _shapeLayer.fillColor     = [UIColor clearColor].CGColor;
    _shapeLayer.strokeColor   = [UIColor redColor].CGColor;
    _shapeLayer.lineWidth     = .f;
    [self.view.layer addSublayer:_shapeLayer];

    // 创建定时器
    _timer = [NSTimer scheduledTimerWithTimeInterval:.f
                                              target:self
                                            selector:@selector(pathAnimation)
                                            userInfo:nil
                                             repeats:YES];

}

/**
 *  执行path的动画
 */
- (void)pathAnimation {
    static int i = ;
    if (i++ %  == ) {
        CABasicAnimation *circleAnim = [CABasicAnimation animationWithKeyPath:@"path"];
        circleAnim.removedOnCompletion = NO;
        circleAnim.duration            = ;
        circleAnim.fromValue           = (__bridge id)[self getStar1BezierPath].CGPath;
        circleAnim.toValue             = (__bridge id)[self getStar2BezierPath].CGPath;
        _shapeLayer.path               = [self getStar2BezierPath].CGPath;
        [_shapeLayer addAnimation:circleAnim forKey:@"animateCirclePath"];
    } else {
        CABasicAnimation *circleAnim = [CABasicAnimation animationWithKeyPath:@"path"];
        circleAnim.removedOnCompletion = NO;
        circleAnim.duration            = ;
        circleAnim.fromValue           = (__bridge id)[self getStar2BezierPath].CGPath;
        circleAnim.toValue             = (__bridge id)[self getStar1BezierPath].CGPath;
        _shapeLayer.path               = [self getStar1BezierPath].CGPath;
        [_shapeLayer addAnimation:circleAnim forKey:@"animateCirclePath"];
    }
}

/**
 *  贝塞尔曲线1
 *
 *  @return 贝塞尔曲线
 */
-(UIBezierPath *)getStar1BezierPath {
    //// Star Drawing
    UIBezierPath* starPath = [UIBezierPath bezierPath];
    [starPath moveToPoint: CGPointMake(22.5, 2.5)];
    [starPath addLineToPoint: CGPointMake(28.32, 14.49)];
    [starPath addLineToPoint: CGPointMake(41.52, 16.32)];
    [starPath addLineToPoint: CGPointMake(31.92, 25.56)];
    [starPath addLineToPoint: CGPointMake(34.26, 38.68)];
    [starPath addLineToPoint: CGPointMake(22.5, 32.4)];
    [starPath addLineToPoint: CGPointMake(10.74, 38.68)];
    [starPath addLineToPoint: CGPointMake(13.08, 25.56)];
    [starPath addLineToPoint: CGPointMake(3.48, 16.32)];
    [starPath addLineToPoint: CGPointMake(16.68, 14.49)];
    [starPath closePath];

    return starPath;
}
/**
 *  贝塞尔曲线2
 *
 *  @return 贝塞尔曲线
 */
-(UIBezierPath *)getStar2BezierPath {
    //// Star Drawing
    UIBezierPath* starPath = [UIBezierPath bezierPath];
    [starPath moveToPoint: CGPointMake(22.5, 2.5)];
    [starPath addLineToPoint: CGPointMake(32.15, 9.21)];
    [starPath addLineToPoint: CGPointMake(41.52, 16.32)];
    [starPath addLineToPoint: CGPointMake(38.12, 27.57)];
    [starPath addLineToPoint: CGPointMake(34.26, 38.68)];
    [starPath addLineToPoint: CGPointMake(22.5, 38.92)];
    [starPath addLineToPoint: CGPointMake(10.74, 38.68)];
    [starPath addLineToPoint: CGPointMake(6.88, 27.57)];
    [starPath addLineToPoint: CGPointMake(3.48, 16.32)];
    [starPath addLineToPoint: CGPointMake(12.85, 9.21)];
    [starPath closePath];

    return starPath;
}

二贝赛尔曲线与CAShapeLayer的关系

1,CAShapeLayer，含shape，顾名思义，它需要一个形状才能生效；

2，贝塞尔曲线可以创建基于矢量的路径

3，贝塞尔曲线给CAShapeLayer提供路径，CAShapeLayer在提供的路径中进行渲染，路径会闭环，所以路径绘制出了shape。

4，用于CAShapeLayer的贝塞尔曲线作为path，其path是一个首尾相接的闭环的曲线，即使该贝塞尔曲线不是一个闭环的曲线。

shape.masksToBounds = YES ; //禁止内容显示超出CAShapeLayer的frame值。

贝塞尔曲线的frame值与CAShapeLayer的frame值互不干扰，CAShaperLayer的frame值不能小于贝塞尔曲线的frame值。

三 CAShapeLayer 之 strokeStart与strokeEnd动画

1，将shapeLayer的fillColor设置为透明背景

2，设置线条的宽度(lineWidth)的值

3，设置线条的颜色

4，将strokeStart值设定为0，然后让stokeEnd的值变化触发隐式动画

   - (void)viewDidLoad {
       [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    // 创建椭圆形贝塞尔曲线
    UIBezierPath *oval        = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(, , , )];

    // 创建CAShapeLayer
    _shapeLayer3               = [CAShapeLayer layer];
    _shapeLayer3.frame         = CGRectMake(, , , );
    _shapeLayer3.position      = self.view.center;

    // 修改CAShapeLayer的线条相关值
    _shapeLayer3.fillColor     = [UIColor clearColor].CGColor;
    _shapeLayer3.strokeColor   = [UIColor redColor].CGColor;
    _shapeLayer3.lineWidth     = .f;

    //0 是最右侧点，0.25是最下方的点，0.5是最左侧的点，0.75是最顶端的点
    _shapeLayer3.strokeStart   = .f;
    _shapeLayer3.strokeEnd     = .f;

    // 建立贝塞尔曲线与CAShapeLayer之间的关联
    _shapeLayer3.path          = oval.CGPath;

    // 添加并显示
    [self.view.layer addSublayer:_shapeLayer3];

    // 创建定时器
    _timer = [NSTimer scheduledTimerWithTimeInterval:.f
                                              target:self
                                            selector:@selector(animationEventTypeTwo)
                                            userInfo:nil
                                             repeats:YES];

}

/**
 *  动画效果1
 */
- (void)animationEventTypeOne {
    // 执行隐式动画
    _shapeLayer3.strokeEnd = arc4random() %  / .f;
}

/**
 *  动画效果2
 */
- (void)animationEventTypeTwo {
    CGFloat valueOne = arc4random() %  / .f;
    CGFloat valueTwo = arc4random() %  / .f;

    // 执行隐式动画
    _shapeLayer3.strokeStart = valueOne < valueTwo ? valueOne : valueTwo;
    _shapeLayer3.strokeEnd   = valueOne > valueTwo ? valueOne : valueTwo;
}

四   贝塞尔曲线 其他方法：

1，根据一个矩形画曲线

+ (UIBezierPath *)bezierPathWithRect:(CGRect)rect

2，根据矩形框的内切圆画曲线

+ (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect

3，

//以某个中心点画弧线

+ (UIBezierPath *)bezierPathWithArcCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise;

参数：

center:弧线中心点的坐标

radius:弧线所在圆的半径

startAngle:弧线开始的角度值

endAngle:弧线结束的角度值

clockwise:是否顺时针画弧线

4，

//画二元曲线，一般和moveToPoint配合使用

- (void)addQuadCurveToPoint:(CGPoint)endPoint controlPoint:(CGPoint)controlPoint

参数：

endPoint:曲线的终点

controlPoint:画曲线的基准点

//以三个点画一段曲线，一般和moveToPoint配合使用

- (void)addCurveToPoint:(CGPoint)endPoint controlPoint1:(CGPoint)controlPoint1 controlPoint2:(CGPoint)controlPoint2

参数：

endPoint:曲线的终点

controlPoint1:画曲线的第一个基准点

controlPoint2:画曲线的第二个基准点