iOSでのUIscrollViewとUIpageControlおよびNSTimerの統合

iOS開発では、UIsCrollViewとUIpageControlをよく使用しています.
次のdemoは両者にNSTimerタイマを加えた後の機能を実現しています

//
//  ViewController.m
//  UI_ScrollView_PageControllDemo
//
//  Created by Devin on 15/11/17.
//  Copyright © 2015  Devin. All rights reserved.
//

#import "ViewController.h"

//             ,       
#define kScreenHeight [UIScreen mainScreen].bounds.size.height
#define kScreenWidth [UIScreen mainScreen].bounds.size.width
CGFloat kImageCount = 10;
CGFloat scrollY = 20;
CGFloat pageCtrlWidth = 200;

@interface ViewController ()<UIScrollViewDelegate>

@property (nonatomic, strong) UIScrollView *scrollView;
@property (nonatomic, strong) UIPageControl *pageCtr;

@property (nonatomic, strong) NSTimer *timer; //        
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self initScrollView];
    [self initPageControl];
    [self addTimer];
}

//    scrollView     
- (void)initScrollView{
    
    self.scrollView = [[UIScrollView alloc] initWithFrame:(CGRectMake(0, scrollY, kScreenWidth, kScreenHeight - scrollY))];
    self.scrollView.delegate = self;
    //          ,               bug,                pagecontrol   ,                 
    self.scrollView.contentOffset = CGPointMake(kScreenWidth, 0);
    
    //   11  ,      ,    ,              ,             ,              
    for (int i = 1; i < kImageCount + 2; i ++) {
        
        CGFloat x = kScreenWidth * i;
        if (i == kImageCount + 1) {
            
            x = 0;
        }
        
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:(CGRectMake(x, scrollY, kScreenWidth, kScreenHeight - scrollY))];
    
        imageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"huoying%d", i]];
        [self.scrollView addSubview:imageView];
    }
    
    self.scrollView.contentSize = CGSizeMake(kScreenWidth * (kImageCount + 1), kScreenHeight - scrollY);
    self.scrollView.pagingEnabled = YES;
    [self.view addSubview:self.scrollView];
}

//   UIPageControl
- (void)initPageControl{
    
    self.pageCtr = [[UIPageControl alloc] initWithFrame:(CGRectMake((kScreenWidth - pageCtrlWidth) / 2, kScreenHeight - scrollY, pageCtrlWidth, scrollY))];
    self.pageCtr.numberOfPages = kImageCount;
    
    self.pageCtr.pageIndicatorTintColor = [UIColor greenColor];
    self.pageCtr.currentPageIndicatorTintColor = [UIColor yellowColor];
    
    //  pageControl  scrollView   
    [self.view insertSubview:self.pageCtr aboveSubview:self.scrollView];
}

#pragma mark --- initTimer
//      
- (void)addTimer{
    
    //         
    self.timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
    
    // NSRunLoop      ,              ,           
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}
- (void)nextPage{
    
    CGPoint offset = self.scrollView.contentOffset;
    
    if (offset.x + kScreenWidth == kScreenWidth * (kImageCount + 1)) {
        
        [self.scrollView setContentOffset:CGPointZero animated:NO];
        [self.scrollView setContentOffset:CGPointMake(kScreenWidth, 0) animated:YES];
    }else{
    
    [self.scrollView setContentOffset:CGPointMake(offset.x + kScreenWidth, 0) animated:YES];
    }
    
    offset = self.scrollView.contentOffset;
    self.pageCtr.currentPage = offset.x / kScreenWidth;
    NSLog(@"%ld", self.pageCtr.currentPage);

}


#pragma mark --- UIScrollView delegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    
    NSInteger page = scrollView.contentOffset.x / kScreenWidth + 0.5; //               ,page  +1
    //              ,       ,  page  -1
    self.pageCtr.currentPage = page - 1;
}

//           
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    
    [self removeTimer];
}

//           
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    
    // GCD,      
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        
        [self addTimer];
    });
}

//     
- (void)removeTimer{
    
    [self.timer invalidate];
    self.timer = nil;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

運転後の効果はこうです