CAGradientLayer

2. 多重渐变

- (void)viewDidLoad {
 [super  viewDidLoad];

  CAGradientLayer *gradientLayer = [CAGradientLayer  layer];
 gradientLayer.frame = self.clipView.bounds;
 [self.clipView.layer addSublayer:gradientLayer];

 gradientLayer.colors = @[(__bridge  id)[UIColor  redColor].CGColor,(__bridge  id)[UIColor  blueColor].CGColor,(__bridge  id)[UIColor  greenColor].CGColor];
 gradientLayer.locations = @[@0.0,@0.25,@0.5];  //必须与colors数组数目一致

 gradientLayer.startPoint = CGPointMake(0, 0);
 gradientLayer.endPoint = CGPointMake(1, 1);
}