iOS 解决1。返回时的黑边问题、2。controller的抖动问题

- (void)loadView {
    [super loadView];
    self.navigationController.navigationBar.hidden = YES;
    return;
}
-(void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:YES];
}