原文地址：http://justsee.iteye.com/blog/1829687
ios4还是3，以前基于在vviewcontroller上的切换，基本上就2中方式，导航控制器上的push，或者普通控制器上modal，现在终于多了一个这种玩意儿了。在ios5中，ViewController中新添加了下面几个方法：
addChildViewController:
removeFromParentViewController
transitionFromViewController:toViewController:duration:options:animations:completion:
willMoveToParentViewController:
didMoveToParentViewController:
下面详细介绍一下addChildViewController，一个ViewController可以添加多个子ViewController，但是这些子ViewControlle要想显示出来，需要把子controller的视图添加到父视图的相应位置r，可以通过transitionFromViewController:toViewController:duration:options:animations:completion:这个方法转换显示的子视图。同时加入相应的动画。下面以一个例子来说明这几个新方法：
下面详细介绍一下上述效果的实现：
创建项目，changeViewController。
添加相应的viewController，MainViewController、FirstViewController、SecondViewController、ThirdViewController。
3.把MainViewController添加到window中。
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
MainViewController *mainViewController=[[MainViewController alloc] initWithNibName:@"MainViewController" bundle:nil];
self.window.rootViewController=mainViewController;
[self.window makeKeyAndVisible];
return YES;
}
4.在MainViewController中添加三个按钮，并且连接onClickbutton方法。
5.在MainViewController中添加三个子controller
#pragma mark – View lifecycle
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
FirstViewController *firstViewController=[[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
[self addChildViewController:firstViewController];
SecondViewController *secondViewController=[[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
[self addChildViewController:secondViewController];
ThirdViewController *thirdViewController=[[ThirdViewController alloc] initWithNibName:@"ThirdViewController" bundle:nil];
[self addChildViewController:thirdViewController];
[contentView addSubview:thirdViewController.view];
currentViewController=thirdViewController;
}
其中要把其中的一个子controller的view添加到根视图中，这样才能显示出相应的视图。
6.点击按钮，切换视图。
-(IBAction)onClickbutton:(id)sender
{
FirstViewController *firstViewController=[self.childViewControllers objectAtIndex:0];
ThirdViewController *thirdViewController=[self.childViewControllers objectAtIndex:2];
SecondViewController *secondViewController=[self.childViewControllers objectAtIndex:1];
if ((currentViewController==firstViewController&&[sender tag]==1)||(currentViewController==secondViewController&&[sender tag]==2) ||(currentViewController==thirdViewController&&[sender tag]==3) ) {
return;
}
UIViewController*oldViewController=currentViewController;
switch ([sender tag]) {
case 1:
{
NSLog(@"留言及回复");
[self transitionFromViewController:currentViewController toViewController:firstViewController duration:4 options:UIViewAnimationOptionTransitionFlipFromLeft animations:^{
} completion:^(BOOL finished) {
if (finished) {
currentViewController=firstViewController;
}else{
currentViewController=oldViewController;
}
}];
}
break;
case 2:
{
NSLog(@"生日提醒");
[self transitionFromViewController:currentViewController toViewController:secondViewController duration:1 options:UIViewAnimationOptionTransitionFlipFromTop animations:^{
} completion:^(BOOL finished) {
if (finished) {
currentViewController=secondViewController;
}else{
currentViewController=oldViewController;
}
}];
}
break;
case 3:
{
NSLog(@"好友申请");
[self transitionFromViewController:currentViewController toViewController:thirdViewController duration:1 options:UIViewAnimationOptionTransitionFlipFromBottom animations:^{
} completion:^(BOOL finished) {
if (finished) {
currentViewController=thirdViewController;
}else{
currentViewController=oldViewController;
}
}];
}
break;
default:
break;
}
}
其中我把按钮设置成不同的tag了。
这时候点击按钮，就可以切换子视图了。
可以看到，这些view在没有使用时，是不会被load的，并且当有Memory Warning时，当前没有显示的view自动被unload掉了。
这样写的好处：
多个UIViewController之间切换可以添加动画
当内存警告的时候，可以把当前不是激活状态的ViewController内存释放。所以新的方法确实能有效地节省内存，也能方便地处理内存不足时的资源回收
可以把代码更好分开
thx google！
iOS5ViewCtrlerSample-master.zip(21.1 KB)
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