看了这位大哥http://www.jobbole.com/members/3170539585/的文章，关于微信导航栏的实现。
由于他没有给出代码实现，当时我没有设置barstyle，导致不好看，哈哈。
这里给出完整代码
`#import “SHNavigationVC.h”

#import “UIColor+expanded.h”
@interface SHNavigationVC ()
@property (nonatomic, strong) UIView *blurBackView;
@end
@implementation SHNavigationVC

• (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  UINavigationBar navBar = self.navigationBar;
  [navBar insertSubview:self.blurBackView atIndex:0];
  }
  -(UIView )blurBackView{
  if (!_blurBackView) {
  _blurBackView = [UIView new];
  _blurBackView.frame = CGRectMake(0, -20, KScreenSize.width, 64);
  CAGradientLayer *gradientLayer = [[CAGradientLayer alloc]init];
  gradientLayer.frame = CGRectMake(0, 0, KScreenSize.width, 64);
  gradientLayer.colors = @[(bridge id)[UIColor colorWithHexString:@”0x040012” andAlpha:0.76].CGColor,(bridge id)[UIColor colorWithHexString:@”0x040012” andAlpha:0.28].CGColor];
  gradientLayer.startPoint = CGPointMake(0, 0);
  gradientLayer.endPoint = CGPointMake(0, 1.0);
  [_blurBackView.layer addSublayer:gradientLayer];
  _blurBackView.userInteractionEnabled = NO;
  _blurBackView.alpha = 0.5;
  }
  return _blurBackView;
  }`