获取图片组中的图片，并实现左右预览和放大效果

实现UIWebView加载网页中的图片的预览放大效果
（1）首先获取到架子啊网页中的图片链接imageUrl，

- (void)webViewDidFinishLoad:(UIWebView *)webView {
//这里是js，主要目的实现对url的获取
static  NSString * const jsGetImages =
@"function getImages(){\
var objs = document.getElementsByTagName(\"img\");\
var imgScr = '';\
for(var i=0;i;//这里获取网页中img标签对象
[webView stringByEvaluatingJavaScriptFromString:jsGetImages];//注入js方法
NSString *urlResurlt = [webView stringByEvaluatingJavaScriptFromString:@"getImages()"]; 
//去掉最后一个空链接+符号
NSString *urlResurltStr = [urlResurlt substringToIndex:([urlResurlt length]-1)];
    
_mUrlArray = [NSMutableArray arrayWithArray:[urlResurltStr componentsSeparatedByString:@"+"]];
 //    NSLog(@"%@",_mUrlArray);
//urlResurlt 就是获取到得所有图片的url的拼接；mUrlArray就是所有Url的数组
}

在下面的方法里进行处理点击图片显示的操作

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
//将url转换为string
NSString *requestString = [[request URL] absoluteString];
//hasPrefix 判断创建的字符串内容是否以pic:字符开始
if ([requestString hasPrefix:@"myweb:imageClick:"]) {
    _imageUrl = [requestString substringFromIndex:@"myweb:imageClick:".length];
    //获取当前图片的url在整个链接地址中位置
    NSInteger index = [_mUrlArray indexOfObject:_imageUrl];
    
    if (self.bgView) {
        //设置不隐藏，还原放大缩小，显示图片
        self.bgView.hidden = NO;
        self.bgView.frame = CGRectMake(0, 0, WIDTH, HEIGHT);
        self.scrollView.contentOffset = CGPointMake(WIDTH*index, 0);
    } else{
        [self showBigImage:_mUrlArray atIndex:index];//创建视图并显示图片
    }
    return NO;
}
return YES;
}

（2）实现放大效果
显示大图，是使用UIScrollView

#pragma mark 显示大图片
- (void)showBigImage:(NSArray *)imageUrls atIndex:(NSInteger )index{
self.bgView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];
[self.bgView setBackgroundColor:[UIColor colorWithWhite:0 alpha:0.7]];
[[UIApplication sharedApplication].keyWindow addSubview:self.bgView];
//创建灰色透明背景，使其背后内容不可操作
self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];
[self.scrollView setBackgroundColor:[UIColor colorWithWhite:0 alpha:0.7]];
self.scrollView.delegate = self;
// 是否分页
self.scrollView.pagingEnabled = YES;
//禁止垂直滚动
  //  self.scrollView.showsVerticalScrollIndicator = YES;
//设置分页
self.scrollView.pagingEnabled = YES;
// 设置内容大小
self.scrollView.contentSize = CGSizeMake(WIDTH*imageUrls.count,HEIGHT);
[self.bgView addSubview:self.scrollView];
//创建关闭按钮
UIButton *closeBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[closeBtn setBackgroundImage:[UIImage imageNamed:@"close"] forState:UIControlStateNormal];
[closeBtn addTarget:self action:@selector(removeBigImage) forControlEvents:UIControlEventTouchUpInside];
[closeBtn setFrame:CGRectMake(WIDTH-50, 25, 25, 25)];
[self.bgView addSubview:closeBtn];
for (int i= 0; i<imageUrls.count; i++) {
    UITapGestureRecognizer *doubleTap =[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleDoubleTap:)];
    [doubleTap setNumberOfTapsRequired:2];
    
    UIScrollView *s = [[UIScrollView alloc]initWithFrame:CGRectMake(WIDTH*i,0,WIDTH, HEIGHT)];
    s.bounces = NO;
    s.backgroundColor = [UIColor clearColor];
    s.contentSize =CGSizeMake(WIDTH,HEIGHT);
    s.delegate =self;
    s.minimumZoomScale =1.0;
    s.maximumZoomScale =3.0;
    //        s.tag = i+1;
    [s setZoomScale:1.0];
    UIImageView *imageview = [[UIImageView alloc]initWithFrame:CGRectMake(0,0,WIDTH, HEIGHT)];
    //加载图片的时候  最好设置一个网络错误的预设图片
    [imageview sd_setImageWithURL:imageUrls[i]];
    imageview.contentMode = UIViewContentModeScaleAspectFit;
    imageview.userInteractionEnabled =YES;
    imageview.tag = i+1;
    [imageview addGestureRecognizer:doubleTap];
    [s addSubview:imageview];
    [self.scrollView addSubview:s];
}
self.scrollView.contentOffset = CGPointMake(WIDTH*index, 0);

}


#pragma mark - ScrollView delegate
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{

for (UIView *v in scrollView.subviews){
    return v;
}
return nil;
}
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
if (scrollView ==self.scrollView){
//        CGFloat x = scrollView.contentOffset.x;
    for (UIScrollView *s in scrollView.subviews){
        if ([s isKindOfClass:[UIScrollView class]]){
            [s setZoomScale:1.0]; //scrollView每滑动一次将要出现的图片较正常时候图片的倍数（将要出现的图片显示的倍数）
        }
    }
}
}

#pragma mark - 双击图片放大的逻辑
-(void)handleDoubleTap:(UIGestureRecognizer *)gesture{
float newScale = [(UIScrollView*)gesture.view.superview zoomScale] * 1.5;//每次双击放大倍数
CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gesture locationInView:gesture.view]];
[(UIScrollView*)gesture.view.superview zoomToRect:zoomRect animated:YES];
}

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center
{
CGRect zoomRect;
zoomRect.size.height =self.view.frame.size.height / scale;
zoomRect.size.width  =self.view.frame.size.width  / scale;
//双击图片的时候 以整个屏幕中心为基点 调整放大后的图片的原点位置
zoomRect.origin.x = self.scrollView.center.x - (zoomRect.size.width  /2.0);
zoomRect.origin.y = self.scrollView.center.y - (zoomRect.size.height /2.0);
return zoomRect;
}
- (void)removeBigImage
{
self.bgView.hidden = YES;
}

2.实现UIImageView图片的预览和放大效果
(1)在图片的点击事件里，进行处理点击图片显示的操作
mUrlArray 是图片数组，index是图片的位置

- (void)showBigImage:(NSArray *)imageUrls atIndex:(NSInteger )index
{
_mUrlArray = imageUrls;
 if (self.bgView) {
        //设置不隐藏，还原放大缩小，显示图片
        self.bgView.hidden = NO;
        self.bgView.frame = CGRectMake(0, 0, WIDTH, HEIGHT);
        self.scrollView.contentOffset = CGPointMake(WIDTH*index, 0);
    } else{
        [self showBigImage:_mUrlArray atIndex:index];//创建视图并显示图片
    }
}插入代码片

(2)实现放大效果
显示大图，是使用UIScrollView
代码同上

附上参考链接：https://www.jianshu.com/p/2bd1eaee206b