iOS 界面启动时，功能新特征显示

APP新启动的时候，都会有几张新的图片滑动，才能到主的界面。现在，我们新建一个控制器，专门来处理新特性，直接上代码.

第一步：新建一个NewfeatureController

//
//  HWNewfeatureController.m
//  Weibo
//
//  Created by jys on 15/3/24.
//  Copyright (c) 2015年 weibo. All rights reserved.
//

#import "HWNewfeatureController.h"
#import "HWTabBarViewController.h"

#define HWNewfeatureCount 4

@interface HWNewfeatureController ()<UIScrollViewDelegate>

@property (nonatomic,weak) UIPageControl *pageControl;
@property (nonatomic,weak) UIScrollView *scrollView;

@end

@implementation HWNewfeatureController

- (void)viewDidLoad {
    [super viewDidLoad];
    //1.创建一个scrollView，显示所有的新特性图片
    UIScrollView *scrollView=[[UIScrollView alloc] init];
    scrollView.frame=self.view.bounds;
    [self.view addSubview:scrollView];
    self.scrollView=scrollView;
    
    //2.添加图片到scrollView中
    CGFloat scrollW=scrollView.width;
    CGFloat scrollH=scrollView.height;
    
    for (int i=0; i<HWNewfeatureCount; i++) {
        UIImageView *imageView=[[UIImageView alloc] init];
        imageView.width=scrollW;
        imageView.height=scrollH;
        imageView.y=0;
        imageView.x=i*scrollW;
        
        //显示图片
        NSString *name = [NSString stringWithFormat:@"new_feature_%d", i + 1];
        imageView.image=[UIImage imageNamed:name];
        [scrollView addSubview:imageView];
        
        // 如果是最后一个imageView，就往里面添加其他内容
        if (i == HWNewfeatureCount - 1) {
            [self setupLastImageView:imageView];
        }
    }
    
    //3.设置scrollView的其它属性
    //如果想要某个方向上不能滚动，那么这个方向对应的尺寸数值传0即可
    scrollView.contentSize=CGSizeMake(scrollView.width*HWNewfeatureCount, 0);
    scrollView.bounces=NO;//去除弹簧效应
    scrollView.pagingEnabled=YES;//分页，一张一张的滚动
    scrollView.showsHorizontalScrollIndicator=NO;//没有滚动条
    scrollView.delegate = self;
    
    //4.添加pageController分页，展示目前看的是第几页
    UIPageControl *pageControl=[[UIPageControl alloc] init];
    pageControl.numberOfPages=HWNewfeatureCount;
    pageControl.backgroundColor=[UIColor redColor];
    pageControl.currentPageIndicatorTintColor=HWColor(253, 98, 42);
    pageControl.pageIndicatorTintColor=HWColor(189, 189, 189);
    pageControl.centerX=scrollW*0.5;
    pageControl.centerY=scrollH-50;
    [self.view addSubview:pageControl];
    self.pageControl=pageControl;
    
    // UIPageControl就算没有设置尺寸，里面的内容还是照常显示的，该控件相对特别
    //    pageControl.width = 100;
    //    pageControl.height = 50;
    //    pageControl.userInteractionEnabled = NO;
}

//当前页面滚到哪页
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    double page=scrollView.contentOffset.x/scrollView.width;
    self.pageControl.currentPage=(int)(page+0.5);
}

/**
 *  初始化最后一个imageView
 *
 *  @param imageView <#imageView description#>
 */
-(void)setupLastImageView:(UIImageView *)imageView
{
    //开启交互功能
    imageView.userInteractionEnabled=YES;
    
    //1.分享给大家
    UIButton *shareBtn=[[UIButton alloc]init];
    [shareBtn setImage:[UIImage imageNamed:@"new_feature_share_false"]  forState:UIControlStateNormal];
    [shareBtn setImage:[UIImage imageNamed:@"new_feature_share_true"] forState:UIControlStateSelected];
    
    [shareBtn setTitle:@"分享给大家" forState:UIControlStateNormal];
    [shareBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    shareBtn.titleLabel.font=[UIFont systemFontOfSize:15];
    shareBtn.width=200;
    shareBtn.height=30;
    shareBtn.centerX=imageView.width*0.5;
    shareBtn.centerY=imageView.height*0.65;
    // top left bottom right
    shareBtn.titleEdgeInsets = UIEdgeInsetsMake(0, 10, 0, 0);
    [shareBtn addTarget:self action:@selector(shareClick:) forControlEvents:UIControlEventTouchUpInside];
    [imageView addSubview:shareBtn];
    
    //2.开始微博
    UIButton *startBtn=[[UIButton alloc] init];
    [startBtn setBackgroundImage:[UIImage imageNamed:@"new_feature_finish_button"] forState:UIControlStateNormal];
    [startBtn setBackgroundImage:[UIImage imageNamed:@"new_feature_finish_button_highlighted"] forState:UIControlStateHighlighted];
    startBtn.size=startBtn.currentBackgroundImage.size;
    startBtn.centerX=imageView.width*0.5;
    startBtn.centerY=imageView.height*0.75;
    [startBtn setTitle:@"开始微博" forState:UIControlStateNormal];
    [startBtn addTarget:self action:@selector(startClick) forControlEvents:UIControlEventTouchUpInside];
    [imageView addSubview:startBtn];
    //startBtn.centerX=imageView
    
}


-(void)shareClick:(UIButton *)shareBtn
{
    //状态取反
    shareBtn.selected=!shareBtn.isSelected;
}

//开始微博
-(void)startClick
{
    UIWindow *window=[UIApplication sharedApplication].keyWindow;
    window.rootViewController=[[HWTabBarViewController alloc]init];
    
}


@end

上面的代码中，需要注意的是：

开始微博，显示主界面时，请使用rootViewController来处理，如果用其它方式，新特性界面并没有销毁，留下隐患。

- (void)startClick
{
    // 切换到HWTabBarController
    /*
     切换控制器的手段
     1.push：依赖于UINavigationController，控制器的切换是可逆的，比如A切换到B，B又可以回到A
     2.modal：控制器的切换是可逆的，比如A切换到B，B又可以回到A
     3.切换window的rootViewController
     */
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    window.rootViewController = [[HWTabBarViewController alloc] init];
    
    // modal方式，不建议采取：新特性控制器不会销毁
//    HWTabBarViewController *main = [[HWTabBarViewController alloc] init];
//    [self presentViewController:main animated:YES completion:nil];
}

第二步，程序启动时，判断版本号。如果版本号不一致，则显示新特性。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // 1.创建窗口
    self.window = [[UIWindow alloc] init];
    self.window.frame = [UIScreen mainScreen].bounds;
    
    // 2.设置根控制器
    NSString *key = @"CFBundleVersion";
    // 上一次的使用版本（存储在沙盒中的版本号）
    NSString *lastVersion = [[NSUserDefaults standardUserDefaults] objectForKey:key];
    // 当前软件的版本号（从Info.plist中获得）
    NSString *currentVersion = [NSBundle mainBundle].infoDictionary[key];
    
    if ([currentVersion isEqualToString:lastVersion]) { // 版本号相同：这次打开和上次打开的是同一个版本
        self.window.rootViewController = [[HWTabBarViewController alloc] init];
    } else { // 这次打开的版本和上一次不一样，显示新特性
        self.window.rootViewController = [[HWNewfeatureViewController alloc] init];
        
        // 将当前的版本号存进沙盒
        [[NSUserDefaults standardUserDefaults] setObject:currentVersion forKey:key];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }
    
    // 3.显示窗口
    [self.window makeKeyAndVisible];
    return YES;
}