CALayer的mask属性

可以对图层按path进行指定裁剪

//#import "ViewController.h"
//
//@interface ViewController ()
//
//@end
//
//@implementation ViewController
//
//- (void)viewDidLoad {
//
//    [super viewDidLoad];
//
//    // 创建一个蓝色的Layer
//    CALayer *foregroundLayer        = [CALayer layer];
//    foregroundLayer.bounds          = CGRectMake(0, 0, 100, 100);
//    foregroundLayer.backgroundColor = [UIColor redColor].CGColor;
//
//    // 创建一个路径
//    UIBezierPath *apath = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(20, 20, 60, 60)];
//
//    // 创建maskLayer
//    CAShapeLayer *maskLayer = [CAShapeLayer layer];
//    maskLayer.path = apath.CGPath;
//    maskLayer.fillColor = [UIColor greenColor].CGColor;
//    maskLayer.fillRule = kCAFillRuleEvenOdd;
//
//    // 设置位置
//    foregroundLayer.position = self.view.center;
//    // 设置mask
//    foregroundLayer.mask = maskLayer;
//
//    [self.view.layer addSublayer:foregroundLayer];
//
//}
//
//@end

#import "ViewController.h"

static CGFloat num;

@interface ViewController ()

@property (nonatomic, strong) CAShapeLayer *circle;
@property (nonatomic, strong) CADisplayLink *link;

@end

@implementation ViewController

@synthesize circle;

- (void)viewDidLoad {

    [super viewDidLoad];

//    //创建一个CAShape
//    CALayer *bgLayer = [CALayer layer];
//
//    //设置大小颜色和位置
//    bgLayer.bounds          = CGRectMake(0, 0, 200, 200);
//    bgLayer.backgroundColor = [UIColor redColor].CGColor;
//    bgLayer.position        = self.view.center;

    CAGradientLayer *bgLayer = [CAGradientLayer layer];
    bgLayer.bounds = CGRectMake(, , , );
    bgLayer.position        = self.view.center;

    bgLayer.colors = [NSArray arrayWithObjects:
                       (id)[UIColor colorWithRed: green:/255.0 blue:/255.0 alpha:1.0].CGColor,
                       (id)[UIColor colorWithRed: green:/255.0 blue:/255.0 alpha:1.0].CGColor,
                       (id)[UIColor whiteColor].CGColor, nil];

    //创建一个CAShapeLayer作为MaskLayer
    circle = [CAShapeLayer layer];

    //设置路径
    circle.path      = [UIBezierPath bezierPathWithArcCenter:CGPointMake(, )
                                                      radius:
                                                  startAngle:
                                                    endAngle: * M_PI
                                                   clockwise:YES].CGPath;
//    circle.lineWidth = 5;
//    circle.fillColor = [UIColor greenColor].CGColor;
//    circle.fillRule  = kCAFillRuleEvenOdd;

    //设置maskLayer
    bgLayer.mask = circle;

    [self.view.layer addSublayer:bgLayer];

    //添加计时器 这个只是一个附加动画
    //self.link = [CADisplayLink displayLinkWithTarget:self selector:@selector(action)];
    //[self.link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
}

- (void)action {

    num ++;

    circle.path      = [UIBezierPath bezierPathWithArcCenter:CGPointMake(, )
                                                      radius: + num
                                                  startAngle:
                                                    endAngle: * M_PI
                                                   clockwise:YES].CGPath;

    if (num > ) {
        [self.link invalidate];
    }
}

@end