iOS 隐藏自定义tabbar

-(void)viewWillAppear:(BOOL)animated
{

NSArray *array=self.tabBarController.view.subviews;

UIView *view=array[2];

view.frame=CGRectMake(0, [UIScreen mainScreen ].bounds.size.height, [UIScreen mainScreen ].bounds.size.width, 49);

[UIView commitAnimations];

}

- (void)viewWillDisappear:(BOOL)animated
{

NSArray *array=self.tabBarController.view.subviews;

UIView *view=array[2];

view.frame=CGRectMake(0, [UIScreen mainScreen ].bounds.size.height-49, [UIScreen mainScreen ].bounds.size.width, 49);

[UIView commitAnimations];
}