转：iOS5中UIViewController新方法的使用

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ViewController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，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，最后的实现效果：

 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 didFinishLauchingWithOptions:(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的视图中添加三个按钮，并且连接onClickButton方法。

5. 在MainViewController中添加三个子controller

- (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;
}

从代码可看出要把其中一个子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;
      }
}

其中把按钮设置成不同的tag了，这样便于我们编程切换子视图。这样的好处：

• 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。

项目源代码：http://easymorse-iphone.googlecode.com/svn/trunk/changeViewController/
本文转载自: http://wangjun.easymorse.com/?p=1630