切换window的root时经常需要一些过度动画，下面是效果的封装

//淡入淡出效果
- (void)animationForRootViewController:(UIViewController *)rootViewController complection:(void(^)(void))complection; {
    self.window.userInteractionEnabled = NO;
    rootViewController.view.alpha = 0;
    [UIView transitionWithView:self.window duration:1.2f options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        self.window.rootViewController = rootViewController;
        rootViewController.view.alpha = 1;
    } completion:^(BOOL finished) {
        self.window.userInteractionEnabled = YES;
        if (complection) {
            complection();
        }
    }];
}

//翻页效果
- (void)animationForRootViewController:(UIViewController *)rootViewController isToLogin:(BOOL)toLogin complection:(void(^)(void))complection; {
    self.window.userInteractionEnabled = NO;
    UIViewAnimationOptions option = toLogin ? UIViewAnimationOptionCurveEaseOut|UIViewAnimationOptionTransitionCurlDown : UIViewAnimationOptionCurveEaseIn|UIViewAnimationOptionTransitionCurlUp;
    [UIView transitionWithView:self.window duration:1.2f options:option animations:^{
        self.window.rootViewController = rootViewController;
    } completion:^(BOOL finished) {
        self.window.userInteractionEnabled = YES;
        if (complection) {
            complection();
        }
    }];
}