iOS navigationbar的高度可以修改吗？

答案是可以修改的。

修改前:

修改后:

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;
}
输出结果:

UINavigationBar:{{0, 20}, {320, 44}}
    _UINavigationBarBackground:{{0, 0}, {320, 44}}
        UIImageView:{{0, 44}, {320, 3}}
    UINavigationItemView:{{160, 22}, {0, 0}}
2013-10-29 20:24:36.900 Nav[8957:907] 

修改后
UINavigationBar:{{0, 20}, {320, 100}}
    _UINavigationBarBackground:{{0, 0}, {320, 100}}
        UIImageView:{{0, 100}, {320, 3}}
    UINavigationItemView:{{160, 22}, {0, 0}}

可以看到UINaigationBar的高度已经从44变到了100. 如果还有疑问，请追问。没有的话，请采纳，谢谢！