小知识点

 //使图片变为圆形

_image.image=[UIImageimageNamed:@"Image"];

    _image.layer.cornerRadius=_image.frame.size.width/2;

    _image.layer.masksToBounds=YES;

    _image.layer.borderColor=[UIColorredColor].CGColor;

    _image.layer.borderWidth=2.0;

  //设置导航栏为透明

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

    [self.navigationController.navigationBarsetShadowImage:[[UIImagealloc]init]];