1.滑动的时候隐藏navigation bar
navigationController.hidesBarsOnSwipe = Yes;
2. 消除导航条返回键带的title
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)
forBarMetrics:UIBarMetricsDefault];
3. 将Navigationbar变成透明而不模糊
[self.navigationController.navigationBar setBackgroundImage:[UIImage new]
forBarMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar .shadowImage = [UIImage new];
self.navigationController.navigationBar .translucent = YES;
