IOS 实现系统UINavigationController UINavigationBar 透明效果

//1.
//将背景图和分隔线都隐藏，这两个NSLog navigationBar 的subView是输出不出来的
//需要时 hidden = NO;
if ([self.navigationController.navigationBar respondsToSelector:@selector(setBackgroundImage:forBarMetrics:)]){
NSArray *list = self.navigationController.navigationBar.subviews;
for (id obj in list) {
if ([obj isKindOfClass:[UIImageView class]]) {
UIImageView *imageView = (UIImageView *)obj;
imageView.hidden = YES;
}
}
}
//2.
//第二个方法会有一条分隔线
//    //透明导航栏
//    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"girl"] forBarMetrics:UIBarMetricsDefault];
//    self.navigationController.navigationBar.barStyle = UIBarMetricsDefault;
//    self.navigationController.navigationBar.translucent = YES;