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];

}