ios 自定义tabbar时 viewDidAppear不调用

自定义tabbar不点击其他item时，默认controller的viewDidAppear的相关函数都不自动调用。在论坛逛了半天终于有人给出正确的解决办法。这里贴出来，以备不时之需。

-(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];
}

在自定义的tabBarViewController中填上这块代码，就能完美解决上述问题。亲测完美解决。