Unbalanced calls to begin/end ap

自定义Tabbar，nav push后出现警告：

Unbalanced calls to begin/end appearance transitions for <>

一个动画没有执行结束，下一个动画就开始了。 解决办法 自定义tabbar实现如下方法 问题即可解决：

-(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];

}