IOS笔记 : addChildViewController

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。

 //在parent view controller 中添加 child view controller
　　 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];

    [self.view  addSubview:thirdViewController.view];

　　// addChildViewController回调用[child willMoveToParentViewController:self] ，但是不会调用didMoveToParentViewController，所以需要显示调用
    [thirdViewController didMoveToParentViewController:self];
    currentViewController=thirdViewController;

　　//切换child view controller
     [self transitionFromViewController:currentViewController toViewController:firstViewController duration:4 options:UIViewAnimationOptionTransitionFlipFromLeft animations:^{
            }  completion:^(BOOL finished) {
               //......
            }];
    currentViewController=firstViewController;

　　//移除child view controller
    // removeFromParentViewController在移除child前不会调用[self willMoveToParentViewController:nil] ，所以需要显示调用
    [currentViewController willMoveToParentViewController:nil];
    [currentViewController removeFromSuperview];
    [currentViewController removeFromParentViewController];