[self.layer setShadowColor:[UIColor blackColor].CGColor];

[self.layer setShadowOpacity:0.8];

[self.layer setShadowOffset:CGSizeMake(, )];

[self.layer setShadowRadius:kShadowRadius];

//加上下面这行即可

[self.layer setShadowPath:[UIBezierPath bezierPathWithRect:self.bounds].CGPath];