iOS内存优化_addChildViewController
iOS的性能优化有很多方面，今天发现虽然很常用但忽视了一个iOS5出现的API，addChildViewController对性能的优化，简单来说就是一个ViewController上面有好多sub View,这些子view不常用但是盖在上面也会耗内存，应该改为ViewController上面加好多sub ViewController,然后不加载sub View,需要用到的时候使用下面这行代码来加载sub View
transitionFromViewController:toViewController:duration:options:animations:completion
那么具体流程是:
1.调用addChildViewController
firstViewController=[[FirstViewController alloc]
initWithNibName:@"FirstViewController" bundle:nil];
[self addChildViewController:firstViewController];
这个时候firstViewController的view是没有加载的，只会调用FirstViewController的willMoveToParentViewController
2.然后真正加载view的时候
[contentView addSubview:thirdViewController.view];
开始调用ViewController的viewDidLoad,viewWillAppear,viewDidAppear方法
3.事先addChildViewController 方法添加了secondViewController，没有加载secondViewController的view，加载的时候用transitionFromViewController从FirstViewController跳转
[self transitionFromViewController:currentViewController toViewController:secondViewController duration:1 options:UIViewAnimationOptionTransitionCurlDown animations:^{
} completion:^(BOOL finished) {
if (finished) {
currentViewController=secondViewController;
}else{
currentViewController=oldViewController;
}
}];
控制器的生命周期如下：
changeViewController[17248:4467101] -[SecondViewController viewDidLoad]
changeViewController[17248:4467101] -[FirstViewController viewWillDisappear:]
hangeViewController[17248:4467101] -[SecondViewController viewWillAppear:]
changeViewController[17248:4467101] -[SecondViewController viewDidAppear:]
changeViewController[17248:4467101] -[FirstViewController viewDidDisappear:]
这是一种性能优化的方式，特此记录
