一般会在次级页面重写viewWillAppear和viewWillDisappear，具体代码如下：
<pre><code>
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.navigationController setNavigationBarHidden:YES animated:YES];
} - (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self.navigationController setNavigationBarHidden:NO animated:YES];
}
</code></pre>
