本来只是打算介绍一下addChildViewController这个方法的,正好今天朋友去换工作面试问到网易新闻标签栏效果的实现,就结合它,用个小Demo实例介绍一下:(具体解释都写在了Demo里面的注释)

//

//  HMTMainViewController.m

//  UIScrollView

//

//  Created by HMT on 14-6-25.

//  Copyright (c) 2014年 humingtao. All rights reserved.

//

#import "HMTMainViewController.h"

#import "HMTFirstViewController.h"

#import "HMTSecondViewController.h"

#import "HMTThirdViewController.h"

@interface HMTMainViewController () <UIScrollViewDelegate>

@property (nonatomic ,strong) HMTThirdViewController  *thirdVC;

@property (nonatomic ,strong) HMTFirstViewController  *firstVC;

@property (nonatomic ,strong) HMTSecondViewController *secondVC;

@property (nonatomic ,strong) UIViewController *currentVC;

@property (nonatomic ,strong) UIScrollView *headScrollView;  //  顶部滚动视图

@property (nonatomic ,strong) NSArray *headArray;

@end

@implementation HMTMainViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

  if (self) {

    // Custom initialization

  }

  return self;

}

- (void)viewDidLoad

{

  [super viewDidLoad];

  // Do any additional setup after loading the view.

  self.navigationItem.title = @"网易新闻Demo";

  self.headArray = @[@"头条",@"娱乐",@"体育",@"财经",@"科技",@"NBA",@"手机"];

  /**

   *   automaticallyAdjustsScrollViewInsets   又被这个属性坑了

   *   我"UI高级"里面一篇文章着重讲了它,大家可以去看看

   */

  self.automaticallyAdjustsScrollViewInsets = NO;

  self.headScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 64, 320, 40)];

  self.headScrollView.backgroundColor = [UIColor purpleColor];

  self.headScrollView.contentSize = CGSizeMake(560, 0);

  self.headScrollView.bounces = NO;

  self.headScrollView.pagingEnabled = YES;

  [self.view addSubview:self.headScrollView];

  for (int i = 0; i < [self.headArray count]; i++) {

    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];

    button.frame = CGRectMake(0 + i*80, 0, 80, 40);

    [button setTitle:[self.headArray objectAtIndex:i] forState:UIControlStateNormal];

    button.tag = i + 100;

    [button addTarget:self action:@selector(didClickHeadButtonAction:) forControlEvents:UIControlEventTouchUpInside];

    [self.headScrollView addSubview:button];

  }

  /*

   苹果新的API增加了addChildViewController方法，并且希望我们在使用addSubview时，同时调用[self addChildViewController:child]方法将sub view对应的viewController也加到当前ViewController的管理中。

   对于那些当前暂时不需要显示的subview，只通过addChildViewController把subViewController加进去；需要显示时再调用transitionFromViewController方法。将其添加进入底层的ViewController中。

   这样做的好处：

   1.无疑，对页面中的逻辑更加分明了。相应的View对应相应的ViewController。

   2.当某个子View没有显示时，将不会被Load，减少了内存的使用。

   3.当内存紧张时，没有Load的View将被首先释放，优化了程序的内存释放机制。

   */

  /**

   *  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:

   */

  self.firstVC = [[HMTFirstViewController alloc] init];

  [self.firstVC.view setFrame:CGRectMake(0, 104, 320, 464)];

  [self addChildViewController:_firstVC];

  self.secondVC = [[HMTSecondViewController alloc] init];

  [self.secondVC.view setFrame:CGRectMake(0, 104, 320, 464)];

  self.thirdVC = [[HMTThirdViewController alloc] init];

  [self.thirdVC.view setFrame:CGRectMake(0, 104, 320, 464)];

  //  默认,第一个视图(你会发现,全程就这一个用了addSubview)

  [self.view addSubview:self.firstVC.view];

  self.currentVC = self.firstVC;

}

- (void)didClickHeadButtonAction:(UIButton *)button

{

  //  点击处于当前页面的按钮,直接跳出

  if ((self.currentVC == self.firstVC && button.tag == 100)||(self.currentVC == self.secondVC && button.tag == 101.)) {

    return;

  }else{

    //  展示2个,其余一样,自行补全噢

    switch (button.tag) {

      case 100:

        [self replaceController:self.currentVC newController:self.firstVC];

        break;

      case 101:

        [self replaceController:self.currentVC newController:self.secondVC];

        break;

      case 102:

        //.......

        break;

      case 103:

        //.......

        break;

      case 104:

        //.......

        break;

      case 105:

        //.......

        break;

      case 106:

        //.......

        break;

        //.......

      default:

        break;

    }

  }

}

//  切换各个标签内容

- (void)replaceController:(UIViewController *)oldController newController:(UIViewController *)newController

{

  /**

   *			着重介绍一下它

   *  transitionFromViewController:toViewController:duration:options:animations:completion:

   *  fromViewController	  当前显示在父视图控制器中的子视图控制器

   *  toViewController		将要显示的姿势图控制器

   *  duration				动画时间(这个属性,old friend 了 O(∩_∩)O)

   *  options				 动画效果(渐变,从下往上等等,具体查看API)

   *  animations			  转换过程中得动画

   *  completion			  转换完成

   */

  [self addChildViewController:newController];

  [self transitionFromViewController:oldController toViewController:newController duration:2.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:nil completion:^(BOOL finished) {

    if (finished) {

      [newController didMoveToParentViewController:self];

      [oldController willMoveToParentViewController:nil];

      [oldController removeFromParentViewController];

      self.currentVC = newController;

    }else{

      self.currentVC = oldController;

    }

  }];

}