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，最后实现的效果：

点击其中的按钮如下：

下面详细介绍一下上述效果的实现：

  1. 创建项目，changeViewController。
  2. 添加相应的viewController，MainViewController、FirstViewController、SecondViewController、ThirdViewController。如下图：

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。

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。
  • 可以把代码更好分开