ios5中UIViewController新使用方法 ( 添加多个子ViewController )

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只有一个是显示到父视图中的，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。

一定要先addChildViewController后才addSubview，否则会出现问题的。

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。