IOS第六天(3:scrollView 图片轮播器)

#import "HMViewController.h"
#define kImageCount     5
@interface HMViewController () <UIScrollViewDelegate>
@property (nonatomic, strong) UIScrollView *scrollView;
@property (nonatomic, strong) UIPageControl *pageControl;

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

@implementation HMViewController

- (UIScrollView *)scrollView
{
if (_scrollView == nil) {
_scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(10, 20, 300, 130)];
_scrollView.backgroundColor = [UIColor redColor];

[self.view addSubview:_scrollView];

// 取消弹簧效果
_scrollView.bounces = NO;

// 取消水平滚动条
_scrollView.showsHorizontalScrollIndicator = NO;
_scrollView.showsVerticalScrollIndicator = NO;

// 要分页
_scrollView.pagingEnabled = YES;

// contentSize
_scrollView.contentSize = CGSizeMake(kImageCount * _scrollView.bounds.size.width, 0);

// 设置代理
_scrollView.delegate = self;
}
return _scrollView;
}

- (UIPageControl *)pageControl
{
if (_pageControl == nil) {
// 分页控件，本质上和scrollView没有任何关系，是两个独立的控件
_pageControl = [[UIPageControl alloc] init];
// 总页数
_pageControl.numberOfPages = kImageCount;
// 控件尺寸
CGSize size = [_pageControl sizeForNumberOfPages:kImageCount];

_pageControl.bounds = CGRectMake(0, 0, size.width, size.height);
_pageControl.center = CGPointMake(self.view.center.x, 130);

// 设置颜色
_pageControl.pageIndicatorTintColor = [UIColor redColor];
_pageControl.currentPageIndicatorTintColor = [UIColor blackColor];

[self.view addSubview:_pageControl];

// 添加监听方法
/** 在OC中，绝大多数"控件"，都可以监听UIControlEventValueChanged事件，button除外" */
[_pageControl addTarget:self action:@selector(pageChanged:) forControlEvents:UIControlEventValueChanged];
}
return _pageControl;
}

// 分页控件的监听方法
- (void)pageChanged:(UIPageControl *)page
{
NSLog(@"%d", page.currentPage);

// 根据页数，调整滚动视图中的图片位置 contentOffset
CGFloat x = page.currentPage * self.scrollView.bounds.size.width;
[self.scrollView setContentOffset:CGPointMake(x, 0) animated:YES];
}

// 视图加载完成调用，通常用来设置数据
- (void)viewDidLoad
{
[super viewDidLoad];

// 设置图片
for (int i = 0; i < kImageCount; i++) {
NSString *imageName = [NSString stringWithFormat:@"img_%02d", i + 1];
UIImage *image = [UIImage imageNamed:imageName];

UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.scrollView.bounds];
imageView.image = image;

[self.scrollView addSubview:imageView];
}

// 计算imageView的位置
[self.scrollView.subviews enumerateObjectsUsingBlock:^(UIImageView *imageView, NSUInteger idx, BOOL *stop) {

// 调整x => origin => frame
CGRect frame = imageView.frame;
frame.origin.x = idx * frame.size.width;

imageView.frame = frame;
}];
//    NSLog(@"%@", self.scrollView.subviews);

// 分页初始页数为0
self.pageControl.currentPage = 0;

// 启动时钟
[self startTimer];
}

- (void)startTimer
{
self.timer = [NSTimer timerWithTimeInterval:2.0 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES];
// 添加到运行循环
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}

- (void)updateTimer
{
// 页号发生变化
// (当前的页数 + 1) % 总页数
int page = (self.pageControl.currentPage + 1) % kImageCount;
self.pageControl.currentPage = page;

NSLog(@"%d", self.pageControl.currentPage);
// 调用监听方法，让滚动视图滚动
[self pageChanged:self.pageControl];
}

#pragma mark - ScrollView的代理方法
// 滚动视图停下来，修改页面控件的小点（页数）
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
// 停下来的当前页数
NSLog(@"%@", NSStringFromCGPoint(scrollView.contentOffset));

// 计算页数
int page = scrollView.contentOffset.x / scrollView.bounds.size.width;

self.pageControl.currentPage = page;
}

/**
修改时钟所在的运行循环的模式后，抓不住图片

解决方法：抓住图片时，停止时钟，送售后，开启时钟
*/
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
NSLog(@"%s", __func__);
// 停止时钟，停止之后就不能再使用，如果要启用时钟，需要重新实例化
[self.timer invalidate];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
NSLog(@"%s", __func__);
[self startTimer];
}
@end