动画切换rootViewController

- (void)restoreRootViewController:(UIViewController *)rootViewController
{

typedef void (^Animation)(void);
UIWindow* window = self.window;

Animation animation = ^{
BOOL oldState = [UIView areAnimationsEnabled];
[UIView setAnimationsEnabled:NO];
window.rootViewController = rootViewController;
[UIView setAnimationsEnabled:oldState];
};

[UIView transitionWithView:window
duration:0.5f
options:UIViewAnimationOptionTransitionCrossDissolve
animations:animation
completion:nil];

}