导航条渐变色

• (void)viewDidLoad {
  [super viewDidLoad];
  [self updateNavigationBarBGColor];
  self.title = @"导航title";
  }

//设置导航条的背景为渐变色

• (void)updateNavigationBarBGColor
  {
  CALayer * bgLayer = [self gradientBGLayerForBounds:CGRectMake(0, 0, self.navigationController.navigationBar.frame.size.width, self.navigationController.navigationBar.frame.size.height)];
  UIGraphicsBeginImageContext(bgLayer.bounds.size);
  [bgLayer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage * bgAsImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  if (bgAsImage != nil)
  {
  [self.navigationController.navigationBar setBackgroundImage:bgAsImage forBarMetrics:UIBarMetricsDefault];
  }
  else
  {
  NSLog(@"Failded to create gradient bg image, user will see standard tint color gradient.");
  }
  }

• (CALayer *)gradientBGLayerForBounds:(CGRect)bounds
  {
  CAGradientLayer *gradientLayer = [CAGradientLayer layer];
  gradientLayer.colors = @[(__bridge id)[UIColor redColor].CGColor, (__bridge id)[UIColor yellowColor].CGColor];
  gradientLayer.locations = @[@0, @1.0];
  gradientLayer.startPoint = CGPointMake(0, 0);
  gradientLayer.endPoint = CGPointMake(1.0, 0);
  gradientLayer.frame = bounds;
  return gradientLayer;
  }

参考原文https://www.jianshu.com/p/6aee372beff2