设置iOS导航栏透明

if (IOS7AndLater) {

        self.automaticallyAdjustsScrollViewInsets =NO;

        [self.navigationController.navigationBarsetBackgroundImage:[[UIImagealloc]init]forBarPosition:UIBarPositionAnybarMetrics:UIBarMetricsDefault];

    }else{

        [self.navigationController.navigationBarsetBackgroundImage:[[UIImagealloc] init]forBarMetrics:UIBarMetricsDefault];

    }

    self.navigationController.navigationBar.shadowImage = [[UIImagealloc] init];