屏幕旋转

iOS屏幕旋转

在设置某个特定的界面可以横屏的时候，跟UINavigationController，UITabbarController相关的控制器，会默认走基类的转屏方法，自己写的不会生效。故要把转屏的控制权交给跟控制器。在子Controller中定义转屏的方向。

/// 跟控制器是UINavigationController
/// 是否允许转屏
- (BOOL)shouldAutorotate {
    return YES;
}

/// 支持的方向
- (UIInterfaceOrientationMask)supportedInterfaceOrientations {
    return [self.viewControllers.lastObject supportedInterfaceOrientations];
}
/// 模态时的方向
- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation {
    return self.topViewController.preferredInterfaceOrientationForPresentation;
}

/// 跟控制器是UITabBarController时
- (BOOL)shouldAutorotate
{
    return YES;
}

- (UIInterfaceOrientationMask)supportedInterfaceOrientations {
    return ((UINavigationController *)self.selectedViewController).topViewController.supportedInterfaceOrientations;
}

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation {
    return ((UINavigationController *)self.selectedViewController).topViewController.preferredInterfaceOrientationForPresentation;
}