IOS修改UINavigationBar高度

你新建一个工程，将UIWindow的rootViewController设置为一个UINavigationController的实列，然后自定义一个控制器CustomVC,在CustomVC中写如下代码:
- (void)viewDidAppear:(BOOL)animated{    [super viewDidAppear:animated];    NSLog(@"修改前");    [self printViewHierarchy:self.navigationController.navigationBar];    //修改NavigaionBar的高度    self.navigationController.navigationBar.frame = CGRectMake(0, 20, 320, 100);    NSLog(@"\n修改后");    [self printViewHierarchy:self.navigationController.navigationBar];}- (void)printViewHierarchy:(UIView *)superView{    static uint level = 0;    for(uint i = 0; i < level; i++){        printf("\t");    }    const char *className = NSStringFromClass([superView class]).UTF8String;    const char *frame = NSStringFromCGRect(superView.frame).UTF8String;    printf("%s:%s\n", className, frame);    ++level;    for(UIView *view in superView.subviews){        [self printViewHierarchy:view];    }    --level;}