YYXC_School/LN_School/SkimViewController.m

#import "SkimViewController.h"

@interface SkimViewController () <UIScrollViewDelegate>
{
    NSArray *_imageNames;
    NSInteger _index;
    
    UIScrollView *_scrollView;
    NSMutableArray *_imageViews;
}
@end

@implementation SkimViewController

- (instancetype)initWithImageNames:(NSArray *)imageNames index:(NSInteger)index
{
    self = [super init];
    if (self) {
        _imageNames = [[NSArray alloc] initWithArray:imageNames];
        _index = index;
    }
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor blackColor];
    
    [self goBackByNavigation];
    [self createScrollView];
    [self creaeteImageViews];
}

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

- (void)createScrollView
{
    CGSize size = self.view.frame.size;
    _scrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
    _scrollView.delegate = self;
    
    if (@available(iOS 11.0, *)) {
        _scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    }else {
        self.automaticallyAdjustsScrollViewInsets = NO;
    }
    _scrollView.pagingEnabled = YES;
    _scrollView.showsHorizontalScrollIndicator = NO;
    
    _scrollView.contentSize = CGSizeMake(size.width*3, size.height);
    _scrollView.contentOffset = CGPointMake(size.width, 0);
    
    [self.view addSubview:_scrollView];
}

- (void)creaeteImageViews
{
    //创建用于保存图片视图的数组
    _imageViews = [[NSMutableArray alloc] init];
    CGSize size = _scrollView.frame.size;
    NSInteger count = _imageNames.count;
    for (NSInteger i=0; i<3; i++) {
        UIImageView *view = [[UIImageView alloc] initWithFrame:CGRectMake(i*size.width, 0, size.width, size.height)];
        view.tag = (i-1+count+_index)%count;
        view.contentMode = UIViewContentModeScaleAspectFit;
        [self setImageToView:view];
        
        if (i != 1) {
            //添加到滚动视图上
            [_scrollView addSubview:view];
        } else {
            //创建一个等大的滚动视图
            UIScrollView *sv = [[UIScrollView alloc] initWithFrame:view.frame];
            //注意 啊 大兄弟
            view.frame = CGRectMake(0, 0, size.width, size.height);
            //缩放比例
            sv.minimumZoomScale = 0.2;
            sv.maximumZoomScale = 2.0;
            
            sv.delegate = self;
            
            //手势
            //长按
            UILongPressGestureRecognizer * pressGestureRecognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressAction:)];
            [view addGestureRecognizer:pressGestureRecognizer];
            
            //单击
            UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapHandle:)];
            [view addGestureRecognizer:tap];
            view.userInteractionEnabled = YES;
            
            [sv addSubview:view];
            [_scrollView addSubview:sv];
            
            //双击手势
            UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapHandle:)];
            doubleTap.numberOfTapsRequired = 2;
            
            //单机必须在双击手势识别失败时,才能识别
            [tap requireGestureRecognizerToFail:doubleTap];
            
            [view addGestureRecognizer:doubleTap];
        }
        
        //保存到数组中
        [_imageViews addObject:view];
        
        
    }
    //刷新标题
    [self refreshTitle];
}

- (void)tapHandle:(UITapGestureRecognizer *)tap
{
    if (tap.numberOfTapsRequired == 1) {
        BOOL hidden = !self.navigationController.navigationBarHidden;
        [self.navigationController setNavigationBarHidden:hidden animated:YES];
    } else if (tap.numberOfTapsRequired == 2) {
        UIScrollView *sv = (UIScrollView *)[tap.view superview];
        if (sv.zoomScale != 1.0) {
            [sv setZoomScale:1.0 animated:YES];
        } else {
            [sv setZoomScale:sv.maximumZoomScale animated:YES];
            [self.navigationController setNavigationBarHidden:YES animated:YES];
        }
    }
    
}

- (void)setImageToView:(UIImageView *)view {

    [view sd_setImageWithURL:[NSURL URLWithString:_imageNames[view.tag]]];
}

- (void)cycleReuse
{
    CGFloat offset = _scrollView.contentOffset.x;
    CGFloat width = _scrollView.frame.size.width;
    NSInteger flag = 0;
    if (offset == 0) {
        //向右滑
        flag = 1;
    } else if (offset == 2*width) {
        //向左滑
        flag = -1;
    } else {
        return;
    }
    NSInteger count = _imageNames.count;
    for (UIImageView *view in _imageViews) {
        view.tag = (view.tag-flag+count)%count;
        [self setImageToView:view];
    }
    //无动画的重置偏移量
    _scrollView.contentOffset = CGPointMake(width, 0);
    
    //刷新标题
    [self refreshTitle];
    //恢复中间滚动视图的缩放比例1.0
    UIScrollView *sv = (UIScrollView *)[_imageViews[1] superview];
    sv.zoomScale = 1.0;
}

- (void)refreshTitle
{
    self.navigationItem.title = [NSString stringWithFormat:@"%ld/%lu",[_imageViews[1] tag]+1,_imageNames.count];
}



#pragma mark 长按保存图片
- (void)longPressAction:(UILongPressGestureRecognizer *)pressGestureRecognizer {
    if (pressGestureRecognizer.state == UIGestureRecognizerStateBegan) {
        UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:@"提示" message:@"保存图片" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
        [alertView show];
    }
}

//保存图片代理方法
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 1) {
        NSURL * url = [NSURL URLWithString:_imageNames[_index]];
        NSURLRequest * request = [NSURLRequest requestWithURL:url];
        NSOperationQueue * queue = [[NSOperationQueue alloc] init];
        [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
            UIImageWriteToSavedPhotosAlbum([UIImage imageWithData:data], self, @selector(image:didFinishSavingWithError:contextInfo:),  nil);
        }];
    }
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    if (!error) {
        ShowMsg(@"已保存到系统相册");
    }else{
        NSLog(@"image = %@, error = %@, contextInfo = %@", image, error, contextInfo);
    }
}

#pragma mark - 代理方法
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self cycleReuse];
}

//不用跟_scrolview区分,因为后者没有设置比例
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return _imageViews[1];
}

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
    //当缩放结束,比例小于0.5时,返回到上一页
    if (scale < 0.5) {
        //返回上一页,显示导航条
        if (self.navigationController.navigationBarHidden) {
            self.navigationController.navigationBarHidden = NO;
        }
        
        [self.navigationController popViewControllerAnimated:YES];
    }
}


@end