你曾注意过Safari移动客户端里美轮美奂的导航栏缩放效果么，以及那些tab bar是如何消失的吗？
在iOS 8中，苹果让这种类型的交互变得非常容易，虽然在WWDC上演示了缩放导航栏效果，不过后来他们用隐藏导航的方式替代了这个想法，但tab bar不包括在内（我猜想他们后期会添加隐藏标签栏的属性）。
以下是iOS 8中非常酷的导航交互方式，可以让用户看到更多内容。
滚动页面时隐藏Bar
如果你有一个Table View,仅需要将导航控件的hidesBarsOnSwipe属性设置为true就OK了。
class QuotesTableViewController: UITableViewController {
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
navigationController?.hidesBarsOnSwipe = true
}
}
注意导航栏的行为会影响到在你的导航堆栈里所有的视图控件，所以如果你希望某一视图控控件的导航条不会跟着隐藏的话，你需要设置一下viewDidAppear。
点击时隐藏
如果你的视图并不像上面所示那样的卷动的话，你可以试着将hidesBarsOnTap的属性设置为true.
class QuoteImageViewController: UIViewController {
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
// 将hidesBarsOnSwift设置为false
// 在此后的这个条件下它不会有任何效果
// 不过在上一个VC中它被设置成了true
navigationController?.hidesBarsOnSwipe = false
// setting hidesBarsOnTap to true
navigationController?.hidesBarsOnTap = true
}
}
请注意，如果你之前在导航栈中某个视图控件里设置过hidesBarOnSwipe,你需要再次将其赋值为false以避免这个视图会发生像其他的视图那样的行为。同样的，如果对于Table View也曾有过设置，那你仍需要重新将navigationController?.hidesBarsOnTap设为false避免出错。
展示键盘输入时隐藏
如上图，使用导航控件的新特性hidesBarsWhenKeyboardAppears，你可以在输入键盘出现时将导航栏隐藏:
class CreateQuoteTableViewController: UITableViewController {
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
navigationController?.hidesBarsOnSwipe = false
// 这个例子恰到好处的结合了hidesBarsOnTap和hidesBarsWhenKeyboardAppears两个特性
// 这样用户可以轻松的唤回导航栏并保存
navigationController?.hidesBarsOnTap = true
navigationController?.hidesBarsWhenKeyboardAppears = true
}
}
为了确保用户在使用时可以轻易的唤出隐藏的导航栏，你应该在需要的时候将hidesBarsOnTap或者hidesBarsOnSwipe设置为true.
其他特性
下面演示的是其他新的导航控制器属性，你可以看一下：
class UINavigationController : UIViewController {
//... truncated
/// When the keyboard appears, the navigation controller's navigationBar toolbar will be hidden. The bars will remain hidden when the keyboard dismisses, but a tap in the content area will show them.
@availability(iOS, introduced=8.0)
var hidesBarsWhenKeyboardAppears: Bool
/// When the user swipes, the navigation controller's navigationBar & toolbar will be hidden (on a swipe up) or shown (on a swipe down). The toolbar only participates if it has items.
@availability(iOS, introduced=8.0)
var hidesBarsOnSwipe: Bool
/// The gesture recognizer that triggers if the bars will hide or show due to a swipe. Do not change the delegate or attempt to replace this gesture by overriding this method.
@availability(iOS, introduced=8.0)
var barHideOnSwipeGestureRecognizer: UIPanGestureRecognizer { get }
/// When the UINavigationController's vertical size class is compact, hide the UINavigationBar and UIToolbar. Unhandled taps in the regions that would normally be occupied by these bars will reveal the bars.
@availability(iOS, introduced=8.0)
var hidesBarsWhenVerticallyCompact: Bool
/// When the user taps, the navigation controller's navigationBar & toolbar will be hidden or shown, depending on the hidden state of the navigationBar. The toolbar will only be shown if it has items to display.
@availability(iOS, introduced=8.0)
var hidesBarsOnTap: Bool
/// The gesture recognizer used to recognize if the bars will hide or show due to a tap in content. Do not change the delegate or attempt to replace this gesture by overriding this method.
@availability(iOS, introduced=8.0)
unowned(unsafe) var barHideOnTapGestureRecognizer: UITapGestureRecognizer { get }
}