自定义TabBarController报错 - Unbalanced calls to begin/end appearance transitions for <>

自定义了TabBarController 之后必须实现以下方法才能避免报错

-(void)viewWillAppear:(BOOL)animated
{
    [self.selectedViewController beginAppearanceTransition: YES animated: animated];
}

-(void) viewDidAppear:(BOOL)animated
{
    [self.selectedViewController endAppearanceTransition];
}

-(void) viewWillDisappear:(BOOL)animated
{
    [self.selectedViewController beginAppearanceTransition: NO animated: animated];
}

-(void) viewDidDisappear:(BOOL)animated
{
    [self.selectedViewController endAppearanceTransition];
}