全屏之后NavigationBar上移20

- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];

    [self prefersStatusBarHidden];

    CGRect windowFrame = [UIScreen mainScreen].bounds;
    
    self.navigationController.navigationBar.frame = CGRectMake(0, 20, windowFrame.size.width, 44);
}