网易新闻标签栏视图切换

原文  http://blog.csdn.net/hmt20130412/article/details/34523235

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;            }  }];}