导航栏如何设置为全透明样式

转载：http://blog.csdn.net/Hierarch_Lee/article/details/50823575

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

self.view.backgroundColor = [UIColor greenColor];

self.navigationController.navigationBar.titleTextAttributes = @{NSForegroundColorAttributeName:[UIColor redColor]};

[self.navigationController.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];

}